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• How can I work efficiently on a desktop sharing workflow?

  - by OSdave

  I am a freelance Magento developer, based in Spain. One of my clients is a Germany based web development company and they're asking me something I think it's impossible. OK, maybe not impossible but definitely not a preferred way of doing things. One of their clients has a Magento Entreprise installation, which is the paid (and I think proprietary) version of Magento. Their client has forbidden them to download the files from his server. My client is asking me now to study one particular module of the application in order to interact with it from a custom module I'll have to develop. As they have a read-only ssh access to their client's server, they came up with this solution: Set up a desktop/screen sharing session between one of their developer's station and mine, alongsides with a skype conversation. Their idea is that I'll say to the developer: show me file foo.php The developer will then open this foo.php file in his IDE. I'll have then to ask him to show me the bar method, the parent class, etc... Remember that it's a read-only session, so forget about putting a Zend_Debug::log() anywhere, and don't even think about a xDebug breakpoint (they don't use any kind of debugger, sic). Their client has also forbidden them to use any version control system... My first reaction when they explained to me this was (and I actually did say it outloud to them): Well, find another client. but they took it as a joke from me. I understand that in a business point of view rejecting a client is not a good practice, but I think that the condition of this assignment make it impossible to complete. At least according to my workflow. I mean, the way I work or learn a new framework/program is: download all files and copy of db on my pc create a git repository and a branch run the application locally use breakpoints use Zend_Debug::log() write the code and tests commit to git repo upload to (test/staging first if there is one, production if not) server I have agreed to try the desktop sharing session, although I think it will be a waste of time. On one hand I don't mind, they pay me for that time, but I know me and I don't like the sensation of loosing my time. On the other hand, I have other clients for whom I can work according to my workflow. I am about to say to them that I cannot (don't want to) do it. Well, I'll first try this desktop sharing session: maybe I'm wrong and it can actually work. But I like to consider myself as a professional, and I know that I don't know everything. So I try to keep an open mind and I am always willing to learn new stuff. So my questions are: Can this desktop-sharing workflow work? What should be done in order to take the most of it? Taking into account all the obstacles (geographic locations, no local, no git), is there another way for me to work on that project?

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• Custom Text and Binary Payloads using WebSocket (TOTD #186)

  - by arungupta

  TOTD #185 explained how to process text and binary payloads in a WebSocket endpoint. In summary, a text payload may be received as public void receiveTextMessage(String message) {    . . . } And binary payload may be received as: public void recieveBinaryMessage(ByteBuffer message) {    . . .} As you realize, both of these methods receive the text and binary data in raw format. However you may like to receive and send the data using a POJO. This marshaling and unmarshaling can be done in the method implementation but JSR 356 API provides a cleaner way. For encoding and decoding text payload into POJO, Decoder.Text (for inbound payload) and Encoder.Text (for outbound payload) interfaces need to be implemented. A sample implementation below shows how text payload consisting of JSON structures can be encoded and decoded. public class MyMessage implements Decoder.Text<MyMessage>, Encoder.Text<MyMessage> {     private JsonObject jsonObject;    @Override    public MyMessage decode(String string) throws DecodeException {        this.jsonObject = new JsonReader(new StringReader(string)).readObject();               return this;    }     @Override    public boolean willDecode(String string) {        return true;    }     @Override    public String encode(MyMessage myMessage) throws EncodeException {        return myMessage.jsonObject.toString();    } public JsonObject getObject() { return jsonObject; }} In this implementation, the decode method decodes incoming text payload to MyMessage, the encode method encodes MyMessage for the outgoing text payload, and the willDecode method returns true or false if the message can be decoded. The encoder and decoder implementation classes need to be specified in the WebSocket endpoint as: @WebSocketEndpoint(value="/endpoint", encoders={MyMessage.class}, decoders={MyMessage.class}) public class MyEndpoint { public MyMessage receiveMessage(MyMessage message) { . . . } } Notice the updated method signature where the application is working with MyMessage instead of the raw string. Note that the encoder and decoder implementations just illustrate the point and provide no validation or exception handling. Similarly Encooder.Binary and Decoder.Binary interfaces need to be implemented for encoding and decoding binary payload. Here are some references for you: JSR 356: Java API for WebSocket - Specification (Early Draft) and Implementation (already integrated in GlassFish 4 promoted builds) TOTD #183 - Getting Started with WebSocket in GlassFish TOTD #184 - Logging WebSocket Frames using Chrome Developer Tools, Net-internals and Wireshark TOTD #185: Processing Text and Binary (Blob, ArrayBuffer, ArrayBufferView) Payload in WebSocket Subsequent blogs will discuss the following topics (not necessary in that order) ... Error handling Interface-driven WebSocket endpoint Java client API Client and Server configuration Security Subprotocols Extensions Other topics from the API

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• Concurrent Affairs

  - by Tony Davis

  I once wrote an editorial, multi-core mania, on the conundrum of ever-increasing numbers of processor cores, but without the concurrent programming techniques to get anywhere near exploiting their performance potential. I came to the.controversial.conclusion that, while the problem loomed for all procedural languages, it was not a big issue for the vast majority of programmers. Two years later, I still think most programmers don't concern themselves overly with this issue, but I do think that's a bigger problem than I originally implied. Firstly, is the performance boost from writing code that can fully exploit all available cores worth the cost of the additional programming complexity? Right now, with quad-core processors that, at best, can make our programs four times faster, the answer is still no for many applications. But what happens in a few years, as the number of cores grows to 100 or even 1000? At this point, it becomes very hard to ignore the potential gains from exploiting concurrency. Possibly, I was optimistic to assume that, by the time we have 100-core processors, and most applications really needed to exploit them, some technology would be around to allow us to do so with relative ease. The ideal solution would be one that allows programmers to forget about the problem, in much the same way that garbage collection removed the need to worry too much about memory allocation. From all I can find on the topic, though, there is only a remote likelihood that we'll ever have a compiler that takes a program written in a single-threaded style and "auto-magically" converts it into an efficient, correct, multi-threaded program. At the same time, it seems clear that what is currently the most common solution, multi-threaded programming with shared memory, is unsustainable. As soon as a piece of state can be changed by a different thread of execution, the potential number of execution paths through your program grows exponentially with the number of threads. If you have two threads, each executing n instructions, then there are 2^n possible "interleavings" of those instructions. Of course, many of those interleavings will have identical behavior, but several won't. Not only does this make understanding how a program works an order of magnitude harder, but it will also result in irreproducible, non-deterministic, bugs. And of course, the problem will be many times worse when you have a hundred or a thousand threads. So what is the answer? All of the possible alternatives require a change in the way we write programs and, currently, seem to be plagued by performance issues. Software transactional memory (STM) applies the ideas of database transactions, and optimistic concurrency control, to memory. However, working out how to break down your program into sufficiently small transactions, so as to avoid contention issues, isn't easy. Another approach is concurrency with actors, where instead of having threads share memory, each thread runs in complete isolation, and communicates with others by passing messages. It simplifies concurrent programs but still has performance issues, if the threads need to operate on the same large piece of data. There are doubtless other possible solutions that I haven't mentioned, and I would love to know to what extent you, as a developer, are considering the problem of multi-core concurrency, what solution you currently favor, and why. Cheers, Tony.

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• PCI Encryption Key Management

  - by Unicorn Bob

  (Full disclosure: I'm already an active participant here and at StackOverflow, but for reasons that should hopefully be obvious, I'm choosing to ask this particular question anonymously). I currently work for a small software shop that produces software that's sold commercially to manage small- to mid-size business in a couple of fairly specialized industries. Because these industries are customer-facing, a large portion of the software is related to storing and managing customer information. In particular, the storage (and securing) of customer credit card information. With that, of course, comes PCI compliance. To make a long story short, I'm left with a couple of questions about why certain things were done the way they were, and I'm unfortunately without much of a resource at the moment. This is a very small shop (I report directly to the owner, as does the only other full-time employee), and the owner doesn't have an answer to these questions, and the previous developer is...err...unavailable. Issue 1: Periodic Re-encryption As of now, the software prompts the user to do a wholesale re-encryption of all of the sensitive information in the database (basically credit card numbers and user passwords) if either of these conditions is true: There are any NON-encrypted pieces of sensitive information in the database (added through a manual database statement instead of through the business object, for example). This should not happen during the ordinary use of the software. The current key has been in use for more than a particular period of time. I believe it's 12 months, but I'm not certain of that. The point here is that the key "expires". This is my first foray into commercial solution development that deals with PCI, so I am unfortunately uneducated on the practices involved. Is there some aspect of PCI compliance that mandates (or even just strongly recommends) periodic key updating? This isn't a huge issue for me other than I don't currently have a good explanation to give to end users if they ask why they are being prompted to run it. Question 1: Is the concept of key expiration standard, and, if so, is that simply industry-standard or an element of PCI? Issue 2: Key Storage Here's my real issue...the encryption key is stored in the database, just obfuscated. The key is padded on the left and right with a few garbage bytes and some bits are twiddled, but fundamentally there's nothing stopping an enterprising person from examining our (dotfuscated) code, determining the pattern used to turn the stored key into the real key, then using that key to run amok. This seems like a horrible practice to me, but I want to make sure that this isn't just one of those "grin and bear it" practices that people in this industry have taken to. I have developed an alternative approach that would prevent such an attack, but I'm just looking for a sanity check here. Question 2: Is this method of key storage--namely storing the key in the database using an obfuscation method that exists in client code--normal or crazy? Believe me, I know that free advice is worth every penny that I've paid for it, nobody here is an attorney (or at least isn't offering legal advice), caveat emptor, etc. etc., but I'm looking for any input that you all can provide. Thank you in advance!

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• Changing the Operating System with only Ubuntu installed

  - by Games Brainiac

  I really wanted to dive into the world of Open Source operating systems, so I downloaded the latest version of Ubuntu (13.10), and installed it on a clean(no operating system installed, absolutely nothing) Lenovo ThinkPad machine. After a few days, I wanted to try out a different Operating System (Elementary OS). I downloaded the ISO file, burned it to a USB, tested that the USB booted from a different computer (I have 2, one is the Lenovo, the other a HP). I was able to get the bootscreen, and everything worked like a charm after I set the BIOS to boot from USB Disk Drive instead of HD. After this, I went back to Lenovo, and tried to open up the boot menu, by pressing F12, so that I could load from a temporary device. To my surprise, nothing but the HD was listed. There was no Optical Drive, No USB Drive, absolutely nothing. So, I thought that these devices were probably disabled. So I went into my BIOS and checked to see what was the case. I saw that all my devices were enabled. USB and all the other devices such as network cable and the rest were all enabled. So, I thought this probably had something to do wit UEFI and Legacy Boot options. So, I made sure that both were enabled. This did not solve the problem either. Again, I got nothing but the option to boot from my Hard Disk. I thought the USB had to be at fault. I tried different ports, but to no avail. Next, I tried with a Live CD, which had Ubuntu on it. This failed too. I simply could not boot from anything other than my hard disk. Okay, so at this point, I was pretty desperate, so I installed Boot-Repair through: sudo add-apt-repository ppa:yannubuntu/boot-repair sudo apt-get update sudo apt-get install boot-repair What this did is lead me to GRUB. Ideally, its just a screen that gives me the option to load from Ubuntu or Advanced Settings. The Advanced settings had nothing but Ubuntu options in it. So, I kept on pressing ESC and that led me to the the grub console, and thats where I am right now with my Lenovo. I've also tried updating the BIOS, but Lenovo only has packages for Red Hat and Windows. So, a dead end there too. Right now, I need to know if there is any way that I can just delete everything from my Lenovo? I want to revert it back to its blank factory condition. How can I achieve this? I have tried to elaborate my problem as best I could. If there is any important information that I've missed out, please do not hesitate to leave a comment. I would have included some screen shots, but BIOS screen shots are a little hard to manage. However, I can provide a camera Image of the boot screen if needed (doing that as we speak).

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• Why is x=x++ undefined?

  - by ugoren

  It's undefined because the it modifies x twice between sequence points. The standard says it's undefined, therefore it's undefined. That much I know. But why? My understanding is that forbidding this allows compilers to optimize better. This could have made sense when C was invented, but now seems like a weak argument. If we were to reinvent C today, would we do it this way, or can it be done better? Or maybe there's a deeper problem, that makes it hard to define consistent rules for such expressions, so it's best to forbid them? So suppose we were to reinvent C today. I'd like to suggest simple rules for expressions such as x=x++, which seem to me to work better than the existing rules. I'd like to get your opinion on the suggested rules compared to the existing ones, or other suggestions. Suggested Rules: Between sequence points, order of evaluation is unspecified. Side effects take place immediately. There's no undefined behavior involved. Expressions evaluate to this value or that, but surely won't format your hard disk (strangely, I've never seen an implementation where x=x++ formats the hard disk). Example Expressions x=x++ - Well defined, doesn't change x. First, x is incremented (immediately when x++ is evaluated), then it's old value is stored in x. x++ + ++x - Increments x twice, evaluates to 2*x+2. Though either side may be evaluated first, the result is either x + (x+2) (left side first) or (x+1) + (x+1) (right side first). x = x + (x=3) - Unspecified, x set to either x+3 or 6. If the right side is evaluated first, it's x+3. It's also possible that x=3 is evaluated first, so it's 3+3. In either case, the x=3 assignment happens immediately when x=3 is evaluated, so the value stored is overwritten by the other assignment. x+=(x=3) - Well defined, sets x to 6. You could argue that this is just shorthand for the expression above. But I'd say that += must be executed after x=3, and not in two parts (read x, evaluate x=3, add and store new value). What's the Advantage? Some comments raised this good point. It's not that I'm after the pleasure of using x=x++ in my code. It's a strange and misleading expression. What I want is to be able to understand complicated expressions. Normally, a complicated expression is no more than the sum of its parts. If you understand the parts and the operators combining them, you can understand the whole. C's current behavior seems to deviate from this principle. One assignment plus another assignment suddenly doesn't make two assignments. Today, when I look at x=x++, I can't say what it does. With my suggested rules, I can, by simply examining its components and their relations.

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• OpenGL Fast-Object Instancing Error

  - by HJ Media Studios

  I have some code that loops through a set of objects and renders instances of those objects. The list of objects that needs to be rendered is stored as a std::map, where an object of class MeshResource contains the vertices and indices with the actual data, and an object of classMeshRenderer defines the point in space the mesh is to be rendered at. My rendering code is as follows: glDisable(GL_BLEND); glEnable(GL_CULL_FACE); glDepthMask(GL_TRUE); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_DEPTH_TEST); for (std::map<MeshResource*, std::vector<MeshRenderer*> >::iterator it = renderables.begin(); it != renderables.end(); it++) { it->first->setupBeforeRendering(); cout << "<"; for (unsigned long i =0; i < it->second.size(); i++) { //Pass in an identity matrix to the vertex shader- used here only for debugging purposes; the real code correctly inputs any matrix. uniformizeModelMatrix(Matrix4::IDENTITY); /** * StartHere fix rendering problem. * Ruled out: * Vertex buffers correctly. * Index buffers correctly. * Matrices correct? */ it->first->render(); } it->first->cleanupAfterRendering(); } geometryPassShader->disable(); glDepthMask(GL_FALSE); glDisable(GL_CULL_FACE); glDisable(GL_DEPTH_TEST); The function in MeshResource that handles setting up the uniforms is as follows: void MeshResource::setupBeforeRendering() { glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); glEnableVertexAttribArray(2); glEnableVertexAttribArray(3); glEnableVertexAttribArray(4); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, iboID); glBindBuffer(GL_ARRAY_BUFFER, vboID); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0); // Vertex position glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 12); // Vertex normal glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 24); // UV layer 0 glVertexAttribPointer(3, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 32); // Vertex color glVertexAttribPointer(4, 1, GL_UNSIGNED_SHORT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 44); //Material index } The code that renders the object is this: void MeshResource::render() { glDrawElements(GL_TRIANGLES, geometry->numIndices, GL_UNSIGNED_SHORT, 0); } And the code that cleans up is this: void MeshResource::cleanupAfterRendering() { glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); glDisableVertexAttribArray(2); glDisableVertexAttribArray(3); glDisableVertexAttribArray(4); } The end result of this is that I get a black screen, although the end of my rendering pipeline after the rendering code (essentially just drawing axes and lines on the screen) works properly, so I'm fairly sure it's not an issue with the passing of uniforms. If, however, I change the code slightly so that the rendering code calls the setup immediately before rendering, like so: void MeshResource::render() { setupBeforeRendering(); glDrawElements(GL_TRIANGLES, geometry->numIndices, GL_UNSIGNED_SHORT, 0); } The program works as desired. I don't want to have to do this, though, as my aim is to set up vertex, material, etc. data once per object type and then render each instance updating only the transformation information. The uniformizeModelMatrix works as follows: void RenderManager::uniformizeModelMatrix(Matrix4 matrix) { glBindBuffer(GL_UNIFORM_BUFFER, globalMatrixUBOID); glBufferSubData(GL_UNIFORM_BUFFER, 0, sizeof(Matrix4), matrix.ptr()); glBindBuffer(GL_UNIFORM_BUFFER, 0); }

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• Using 3rd Party JavaScript Plugins Hardwired With &lsquo;document.write&rsquo;

  - by ToStringTheory

  Introduction Have you ever had the need to implement a 3rd party JavaScript plugin, but your needs didn’t fit the model and usage defined by the API or documentation of the plugin?  Recently I ran into this issue when I was trying to implement a web snapshot plugin into our site.  To use their plugin, you had to include a script tag to the plugin on their server with an API key.  The second part of the usage was to include a <script> tag around a function call wherever you wanted a snapshot to appear. The Problem When trying to use the service, the images did not display.  I checked a couple of things and didn’t find anything wrong at first..  It wasn’t until I looked at the function that was called by the inline script did I find the issue – a call to the webservice, followed by a call to ‘document.write’ in its callback.  The solution in which I was trying to implement the plugin happened to be in response to an AJAX call after the document had completely loaded.  After the page has loaded, document.write does nothing. My first thought for a solution was to just cache the script from the service, and edit it do something like a return function or callback that I could use to edit the document from.  However, I quickly discovered that there is no way to cache the script from the service, as it had a hash in the function where it would call the server.  The hash was updated every few seconds/minutes, expiring old hashes.  This meant that I wouldn’t be able to edit the script and upload a new version to my server, as the script would not work after a few minutes from originally getting the script from the service. Solution The solution eluded me until I realized that this was JavaScript I was dealing with.  A language designed so that you could do just about anything to any library, function, or object…  At this point, the solution was simple – take control of the document.write function.  Using a buffer variable, and a simple function call, it is eerily simple to perform: //what would have been output to the document var buffer = ""; //store a reference to the real document.write var dw = document.write; //redefine document.write to store to our buffer document.write = function (str) {buffer += str;} //execute the function containing calls to document.write eval('{function encapsulated in <script></script> tags}'); //restore the original document.write function (just in case) document.write = dw; That’s it.  Instead of using the script tags where I wanted to include a snapshot, I called a function passing in the URL to the page I wanted a snapshot of.  After that last line of code, what would have been output to the document (or not in the case of the ajax call) was instead stored in buffer. Conclusion While the solution itself is simple, coming from a background much more footed in the .Net platform, I believe that this is a prime example of always keeping the language that you are working in in mind.  While this may seem obvious at first, as I KNEW I was in JavaScript, I never thought of taking control of the document.write function because I am more accustomed to the .Net world.  I can’t simply replace the functionality of Console.WriteLine.

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• Bowing to User Experience

  As a consumer of geeky news it is hard to check my Google Reader without running into two or three posts about Apples iPad and in particular the changes to the developer guidelines which seemingly restrict developers to using Apples Xcode tool and Objective-C language for iPad apps. One of the alternatives to Objective-C affected, is MonoTouch, an option with some appeal to me as it is based on the Mono implementation of C#. Seemingly restricted is the key word here, as far as I can tell, no official announcement has been made about its fate. For more details around MonoTouch for iPhone OS, check out Miguel de Icazas post: http://tirania.org/blog/archive/2010/Apr-28.html. These restrictions have provoked some outrage as the perception is that Apple is arrogantly restricting developers freedom to create applications as they choose and perhaps unwittingly shortchanging iPhone/iPad users who wont benefit from these now never-to-be-made great applications. Apples response has mostly been to say they are concentrating on providing a certain user experience to their customers, and to do this, they insist everyone uses the tools they approve. Which isnt a surprising line of reasoning given Apple restricts the hardware used and content of the apps already. The vogue term for this approach is curated, as in a benevolent museum director selecting only the finest artifacts for display or a wise gardener arranging the plants in a garden just so. If this is what a curated experience is like it is hard to argue that consumers are not responding. My iPhone is probably the most satisfying piece of technology I own. Coming from the Razr, it really was an revolution in how the form factor, interface and user experience all tied together. While the curated approach reinvented the smart phone genre, it is easy to forget that this is not a new approach for Apple. Macbooks and Macs are Apple hardware that run Apple software. And theyve been successful, but not quite in the same way as the iPhone or iPad (based on early indications). Why not? Well a curated approach can only be wildly successful if the curator a) makes the right choices and b) offers choices that no one else has. Although its advantages are eroding, the iPhone was different from other phones, a unique, focused, touch-centric experience. The iPad is an attempt to define another category of computing. Macs and Macbooks are great devices, but are not fundamentally a different user experience than a PC, you still have windows, file folders, mouse and keyboard, and similar applications. So the big question for Apple is can they hold on to their market advantage, continuing innovating in user experience and stay on top? Or are they going be like Xerox, and the rest of the world says thank you for the windows metaphor, now let me implement that better? It will be exciting to watch, with Android already a viable competitor and Microsoft readying Windows Phone 7. And to close the loop back to the restrictions on developing for iPhone OS. At this point the main target appears to be Adobe and Adobe Flash. Apples calculation is that a) they dont need those developers or b) the developers they want will learn Apples stuff anyway. My guess is that they are correct; that as much as I like the idea of developers having more options, I am not going to buy a competitors product to spite Apple unless that product is just as usable. For a non-technical consumer, I dont know that this conversation even factors into the buying decision. If it did, wed be talking about how Microsoft is trying to retake a slice of market share from the behemoth that is Linux.Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Too complex/too many objects?

  - by Mike Fairhurst

  I know that this will be a difficult question to answer without context, but hopefully there are at least some good guidelines to share on this. The questions are at the bottom if you want to skip the details. Most are about OOP in general. Begin context. I am a jr dev on a PHP application, and in general the devs I work with consider themselves to use many more OO concepts than most PHP devs. Still, in my research on clean code I have read about so many ways of using OO features to make code flexible, powerful, expressive, testable, etc. that is just plain not in use here. The current strongly OO API that I've proposed is being called too complex, even though it is trivial to implement. The problem I'm solving is that our permission checks are done via a message object (my API, they wanted to use arrays of constants) and the message object does not hold the validation object accountable for checking all provided data. Metaphorically, if your perm containing 'allowable' and 'rare but disallowed' is sent into a validator, the validator may not know to look for 'rare but disallowed', but approve 'allowable', which will actually approve the whole perm check. We have like 11 validators, too many to easily track at such minute detail. So I proposed an AtomicPermission class. To fix the previous example, the perm would instead contain two atomic permissions, one wrapping 'allowable' and the other wrapping 'rare but disallowed'. Where previously the validator would say 'the check is OK because it contains allowable,' now it would instead say '"allowable" is ok', at which point the check ends...and the check fails, because 'rare but disallowed' was not specifically okay-ed. The implementation is just 4 trivial objects, and rewriting a 10 line function into a 15 line function. abstract class PermissionAtom { public function allow(); // maybe deny() as well public function wasAllowed(); } class PermissionField extends PermissionAtom { public function getName(); public function getValue(); } class PermissionIdentifier extends PermissionAtom { public function getIdentifier(); } class PermissionAction extends PermissionAtom { public function getType(); } They say that this is 'not going to get us anything important' and it is 'too complex' and 'will be difficult for new developers to pick up.' I respectfully disagree, and there I end my context to begin the broader questions. So the question is about my OOP, are there any guidelines I should know: is this too complicated/too much OOP? Not that I expect to get more than 'it depends, I'd have to see if...' when is OO abstraction too much? when is OO abstraction too little? how can I determine when I am overthinking a problem vs fixing one? how can I determine when I am adding bad code to a bad project? how can I pitch these APIs? I feel the other devs would just rather say 'its too complicated' than ask 'can you explain it?' whenever I suggest a new class.

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• Entity System with C++ templates

  - by tommaisey

  I've been getting interested in the Entity/Component style of game programming, and I've come up with a design in C++ which I'd like a critique of. I decided to go with a fairly pure Entity system, where entities are simply an ID number. Components are stored in a series of vectors - one for each Component type. However, I didn't want to have to add boilerplate code for every new Component type I added to the game. Nor did I want to use macros to do this, which frankly scare me. So I've come up with a system based on templates and type hinting. But there are some potential issues I'd like to check before I spend ages writing this (I'm a slow coder!) All Components derive from a Component base class. This base class has a protected constructor, that takes a string parameter. When you write a new derived Component class, you must initialise the base with the name of your new class in a string. When you first instantiate a new DerivedComponent, it adds the string to a static hashmap inside Component mapped to a unique integer id. When you subsequently instantiate more Components of the same type, no action is taken. The result (I think) should be a static hashmap with the name of each class derived from Component that you instantiate at least once, mapped to a unique id, which can by obtained with the static method Component::getTypeId ("DerivedComponent"). Phew. The next important part is TypedComponentList<typename PropertyType>. This is basically just a wrapper to an std::vector<typename PropertyType> with some useful methods. It also contains a hashmap of entity ID numbers to slots in the array so we can find Components by their entity owner. Crucially TypedComponentList<> is derived from the non-template class ComponentList. This allows me to maintain a list of pointers to ComponentList in my main ComponentManager, which actually point to TypedComponentLists with different template parameters (sneaky). The Component manager has template functions such as: template <typename ComponentType> void addProperty (ComponentType& component, int componentTypeId, int entityId) and: template <typename ComponentType> TypedComponentList<ComponentType>* getComponentList (int componentTypeId) which deal with casting from ComponentList to the correct TypedComponentList for you. So to get a list of a particular type of Component you call: TypedComponentList<MyComponent>* list = componentManager.getComponentList<MyComponent> (Component::getTypeId("MyComponent")); Which I'll admit looks pretty ugly. Bad points of the design: If a user of the code writes a new Component class but supplies the wrong string to the base constructor, the whole system will fail. Each time a new Component is instantiated, we must check a hashed string to see if that component type has bee instantiated before. Will probably generate a lot of assembly because of the extensive use of templates. I don't know how well the compiler will be able to minimise this. You could consider the whole system a bit complex - perhaps premature optimisation? But I want to use this code again and again, so I want it to be performant. Good points of the design: Components are stored in typed vectors but they can also be found by using their entity owner id as a hash. This means we can iterate them fast, and minimise cache misses, but also skip straight to the component we need if necessary. We can freely add Components of different types to the system without having to add and manage new Component vectors by hand. What do you think? Do the good points outweigh the bad?

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• Using Private Extension Galleries in Visual Studio 2012

  - by Jakob Ehn

  Note: The installer and the complete source code is available over at CodePlex at the following location: http://inmetavsgallery.codeplex.com   Extensions and addins are everywhere in the Visual Studio ALM ecosystem! Microsoft releases new cool features in the form of extensions and the list of 3rd party extensions that plug into Visual Studio just keeps growing. One of the nice things about the VSIX extensions is how they are deployed. Microsoft hosts a public Visual Studio Gallery where you can upload extensions and make them available to the rest of the community. Visual Studio checks for updates to the installed extensions when you start Visual Studio, and installing/updating the extensions is fast since it is only a matter of extracting the files within the VSIX package to the local extension folder. But for custom, enterprise-specific extensions, you don’t want to publish them online to the whole world, but you still want an easy way to distribute them to your developers and partners. This is where Private Extension Galleries come into play. In Visual Studio 2012, it is now possible to add custom extensions galleries that can point to any URL, as long as that URL returns the expected content of course (see below).Registering a new gallery in Visual Studio is easy, but there is very little documentation on how to actually host the gallery. Visual Studio galleries uses Atom Feed XML as the protocol for delivering new and updated versions of the extensions. This MSDN page describes how to create a static XML file that returns the information about your extensions. This approach works, but require manual updates of that file every time you want to deploy an update of the extension. Wouldn’t it be nice with a web service that takes care of this for you, that just lets you drop a new version of your VSIX file and have it automatically detect the new version and produce the correct Atom Feed XML? Well search no more, this is exactly what the Inmeta Visual Studio Gallery Service does for you :-) Here you can see that in addition to the standard Online galleries there is an Inmeta Gallery that contains two extensions (our WIX templates and our custom TFS Checkin Policies). These can be installed/updated i the same way as extensions from the public Visual Studio Gallery. Installing the Service Download the installler (Inmeta.VSGalleryService.Install.msi) for the service and run it. The installation is straight forward, just select web site, application pool and (optional) a virtual directory where you want to install the service.   Note: If you want to run it in the web site root, just leave the application name blank Press Next and finish the installer. Open web.config in a text editor and locate the the <applicationSettings> element Edit the following setting values: FeedTitle This is the name that is shown if you browse to the service using a browser. Not used by Visual Studio BaseURI When Visual Studio downloads the extension, it will be given this URI + the name of the extension that you selected. This value should be on the following format: http://SERVER/[VDIR]/gallery/extension/ VSIXAbsolutePath This is the path where you will deploy your extensions. This can be a local folder or a remote share. You just need to make sure that the application pool identity account has read permissions in this folder Save web.config to finish the installation Open a browser and enter the URL to the service. It should show an empty Feed page:   Adding the Private Gallery in Visual Studio 2012 Now you need to add the gallery in Visual Studio. This is very easy and is done as follows: Go to Tools –> Options and select Environment –> Extensions and Updates Press Add to add a new gallery Enter a descriptive name, and add the URL that points to the web site/virtual directory where you installed the service in the previous step   Press OK to save the settings. Deploying an Extension This one is easy: Just drop the file in the designated folder! :-)  If it is a new version of an existing extension, the developers will be notified in the same way as for extensions from the public Visual Studio gallery: I hope that you will find this sever useful, please contact me if you have questions or suggestions for improvements!

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• How to introduce a computer illiterate 50-year old to programming [closed]

  - by sunday

  The other day my dad asked me a question that I would have never expected from him. "How can I learn C++?" My dad is turning 56 this year and computers are a distant concept for him. He doesn't know how to use a phone very well besides calling numbers (no speed dial or contacts); though he has started to learn computers a little better - to the point that he knows how to open the internet (in Windows) and browse around (and has successfully completed several job applications entirely on his own online, of which he was offered positions too). But still, these are too narrow-windowed experiences to mean much, really. While he may not have the background, my dad knows how to read. And I mean reading as a skill, not just an ability. He has little to no college education (financial problems, family, etc.) and was fortunate enough to finish high school, but still taught himself to become a master electrician and has been one for almost 30 years now. He did the same with guitar, learning to play at a very professional level and has been praised for his skill. In high school, he picked up a weight lifting book - and was the only person in his high school at the time to qualify officially as an "athlete" by national standards. In all cases, he just needed something to read. Something to teach him. He absorbs information like a sponge. I have no doubt in my dad's motivation or capability of doing this, so my general goal is simply: Get my dad into the world of computers, and get him on the road to programming. I strongly believe that once I get him through the fundamentals, his drive and reading skill will keep him going on this own. So I'm asking you all: where should I start with all this? And what are the best resources out there? Should I get him to start Linux instead of Windows? Is C++ a bad idea? Remember, he needs to (IMO) learn computers first, and then get that first grasp (the "Hello world" experience) of programming. For money's sake and at top preference, I'd like free online resources that he can read, but by all means any good suggestions in print or paid-for-online are welcome (that I could possibly look into later to purchase). And also, I intend to start him off with C++ (no Python, Java, etc.), because I know it the best and will be able to help him along the way with code. (I have minimal knowledge right now in other languages). Edit: I'm getting a lot of persistent suggestions to use Python. The only reason I wanted to do C++ is that I KNOW it and can be THERE when my dad needs help. My VERY FIRST exposure to programming ever was Java. I learned Java, and I got good at it. I open to other suggestions, but please provide an effective application of your suggestions. EDIT #2: I understand my approach/thinking/knowledge could be lacking here. I'm a sophomore level undergraduate CS major. If you don't agree with anything in my post, tell me why - give me ideas, information - that's why I'm asking in the first place. To narrow down my general goal to specific reachable goals.

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• Why is the framerate (fps) capped at 60?

  - by dennmat

  ISSUE I recently moved a project from my laptop to my desktop(machine info below). On my laptop the exact same code displays the fps(and ms/f) correctly. On my desktop it does not. What I mean by this is on the laptop it will display 300 fps(for example) where on my desktop it will show only up to 60. If I add 100 objects to the game on the laptop I'll see my frame rate drop accordingly; the same test on the desktop results in no change and the frames stay at 60. It takes a lot(~300) entities before I'll see a frame drop on the desktop, then it will descend. It seems as though its "theoretical" frames would be 400 or 500 but will never actually get to that and only do 60 until there's too much to handle at 60. This 60 frame cap is coming from no where. I'm not doing any frame limiting myself. It seems like something external is limiting my loop iterations on the desktop, but for the last couple days I've been scratching my head trying to figure out how to debug this. SETUPS Desktop: Visual Studio Express 2012 Windows 7 Ultimate 64-bit Laptop: Visual Studio Express 2010 Windows 7 Ultimate 64-bit The libraries(allegro, box2d) are the same versions on both setups. CODE Main Loop: while(!abort) { frameTime = al_get_time(); if (frameTime - lastTime >= 1.0) { lastFps = fps/(frameTime - lastTime); lastTime = frameTime; avgMspf = cumMspf/fps; cumMspf = 0.0; fps = 0; } /** DRAWING/UPDATE CODE **/ fps++; cumMspf += al_get_time() - frameTime; } Note: There is no blocking code in the loop at any point. Where I'm at My understanding of al_get_time() is that it can return different resolutions depending on the system. However the resolution is never worse than seconds, and the double is represented as [seconds].[finer-resolution] and seeing as I'm only checking for a whole second al_get_time() shouldn't be responsible. My project settings and compiler options are the same. And I promise its the same code on both machines. My googling really didn't help me much, and although technically it's not that big of a deal. I'd really like to figure this out or perhaps have it explained, whichever comes first. Even just an idea of how to go about figuring out possible causes, because I'm out of ideas. Any help at all is greatly appreciated. EDIT: Thanks All. For any others that find this to disable vSync(windows only) in opengl: First get "wglext.h". It's all over the web. Then you can use a tool like GLee or just write your own quick extensions manager like: bool WGLExtensionSupported(const char *extension_name) { PFNWGLGETEXTENSIONSSTRINGEXTPROC _wglGetExtensionsStringEXT = NULL; _wglGetExtensionsStringEXT = (PFNWGLGETEXTENSIONSSTRINGEXTPROC) wglGetProcAddress("wglGetExtensionsStringEXT"); if (strstr(_wglGetExtensionsStringEXT(), extension_name) == NULL) { return false; } return true; } and then create and setup your function pointers: PFNWGLSWAPINTERVALEXTPROC wglSwapIntervalEXT = NULL; PFNWGLGETSWAPINTERVALEXTPROC wglGetSwapIntervalEXT = NULL; if (WGLExtensionSupported("WGL_EXT_swap_control")) { // Extension is supported, init pointers. wglSwapIntervalEXT = (PFNWGLSWAPINTERVALEXTPROC) wglGetProcAddress("wglSwapIntervalEXT"); // this is another function from WGL_EXT_swap_control extension wglGetSwapIntervalEXT = (PFNWGLGETSWAPINTERVALEXTPROC) wglGetProcAddress("wglGetSwapIntervalEXT"); } Then just call wglSwapIntervalEXT(0) to disable vSync and 1 to enable vSync. I found the reason this is windows only is that openGl actually doesn't deal with anything other than rendering it leaves the rest up to the OS and Hardware. Thanks everyone saved me a lot of time!

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• Software and/(x)or Hardware Projects for Pre-School Kids

  - by haylem

  I offered to participate at my kid's pre-school for various activities (yes, I'm crazy like that), and one of them is to help them discover extra-curricular (big word for a pre-school, but by lack of a better one... :)) hobbies, which may or may not relate to a professional activity. At first I thought that it wouldn't be really easy to have pre-schoolers relate to programming or the internal workings of a computer system in general (and I'm more used to teaching middle-school to university-level students), but then I thought there must be a way. So I'm trying to figure out ways to introduce very young kids (3yo) to computer systems in a fun and preferably educational way. Of course, I don't expect them to start smashing the stack for fun and profit right away (or at least not voluntarily, though I could use the occasion for some toddler tests...), but I'm confident there must be ways to get them interested in both: using the systems, becoming curious about understanding what they do, interacting with the systems to modify them. I guess this setting is not really relevant after all, it's pretty much the same as if you were aiming to achieve the same for your own kids at home. Ideas Considering we're talking 3yo pre-schoolers here, and that at this age some kids are already quite confident using a mouse (some even a keyboard, if not for typing, at least to press some buttons they've come to associate with actions) while others have not yet had any interaction with computers of any kind, it needs to be: rather basic, demonstrated and played with in less then 5 or 10 minutes, doable in in groups or alone, scalable and extendable in complexity to accommodate their varying abilities. The obvious options are: basic smallish games to play with, interactive systems like LOGO, Kojo, Squeak and clones (possibly even simpler than that), or thngs like Lego Systems. I guess it can be a thing to reflect on both at the software and the hardware levels: it could be done with a desktop or laptop machine, a tablet, a smartphone (or a crap-phone, for that matter, as long as you can modify it), or even get down to building something from scratch (Raspberry Pi and Arduino being popular options at the moment). I can probably be in the form of games, funny visualizations (which are pretty much games) w/ Prototype, virtual worlds to explore. I also thought on the moment (and I hope this won't offend anyone) that some approaches to teaching pets could work (reward systems, haptic feedback and such things could quickly point a kid in the right direction to understanding how things work, in a similar fashion - I'm not suggesting to shock the kids!). Hmm, Is There an Actual Question in There? What type of systems do you think might be a good fit, both in terms of hardware and software? Do you have seen such systems, or have anything in mind to work on? Are you aware of some research in this domain, with tangible results? Any input is welcome. It's not that I don't see options: there are tons, but I have a harder time pinpointing a more concrete and definite type of project/activity, so I figure some have valuable ideas or existing ones. Note: I am not advocating that every kid should learn to program, be interested in computer systems, or that all of them in a class would even care enough to follow such an introduction with more than a blank stare. I don't buy into the "everybody would benefit from learning to program" thing. Wouldn't hurt, but not necessary in any way. But if I can walk out of there with a few of them having smiled using the thing (or heck, cried because others took them away from them), that'd be good enough. Related Questions I've seen and that seem to complement what I'm looking for, but not exactly for the same age groups or with the same goals: Teaching Programming to Kids Recommendations for teaching kids math concepts & skills for programming?

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• Upgrade to Xubuntu 13.10 - Saucy Salamander

  As a common 'fashion' it is possible to upgrade an existing installation of Ubuntu or one of its derivates every six months. Of course, you might opt-in for the adventure and directly keep your system always on the latest version (including alphas and betas), or you might like to play safe and stay on the long-term support (LTS) versions which are updated every two years only. As for me, I'd like to jump from release to release on my main desktop machine. And since 17th October Saucy Salamander or also known as Ubuntu 13.10 has been released for general use. The following paragraphs document the steps I went in order to upgrade my system to the recent version. Don't worry about the fact that I'm actually using Xubuntu. It's mainly a flavoured version of Ubuntu running Xfce 4.10 as default X Window manager. Well, I have Gnome and LXDE on the same system... just out of couriosity. Preparing the system Before you think about upgrading you have to ensure that your current system is running on the latest packages. This can be done easily via a terminal like so: $ sudo apt-get update && sudo apt-get -y dist-upgrade --fix-missing Next, we are going to initiate the upgrade itself: $ sudo update-manager As a result the graphical Software Updater should inform you that a newer version of Ubuntu is available for installation. Ubuntu's Software Updater informs you whether an upgrade is available Running the upgrade After clicking 'Upgrade...' you will be presented with information about the new version. Details about Ubuntu 13.10 (Saucy Salamander) Simply continue with the procedure and your system will be analysed for the next steps. Analysing the existing system and preparing the actual upgrade to 13.10 Next, we are at the point of no return. Last confirmation dialog before having a coffee break while your machine is occupied to download the necessary packages. Not the best bandwidth at hand after all... yours might be faster. Are you really sure that you want to start the upgrade? Let's go and have fun! Anyway, bye bye Raring Ringtail and Welcome Saucy Salamander! In case that you added any additional repositories like Medibuntu or PPAs you will be informed that they are going to be disabled during the upgrade and they might require some manual intervention after completion. Ubuntu is playing safe and third party repositories are disabled during the upgrade Well, depending on your internet bandwidth this might take something between a couple of minutes and some hours to download all the packages and then trigger the actual installation process. In my case I left my PC unattended during the night. Time to reboot Finally, it's time to restart your system and see what's going to happen... In my case absolutely nothing unexpected. The system booted the new kernel 3.11.0 as usual and I was greeted by a new login screen. Honestly, 'same' system as before - which is good and I love that fact of consistency - and I can continue to work productively. And also Software Updater confirms that we just had a painless upgrade: System is running Ubuntu 13.10 - Saucy Salamander - and up to date See you in six months again... ;-) Post-scriptum In case that you would to upgrade to the latest development version of Ubuntu, run the following command in a console: $ sudo update-manager -d And repeat all steps as described above.

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• Identity in .NET 4.5&ndash;Part 3: (Breaking) changes

  - by Your DisplayName here!

  I recently started porting a private build of Thinktecture.IdentityModel to .NET 4.5 and noticed a number of changes. The good news is that I can delete large parts of my library because many features are now in the box. Along the way I found some other nice additions. ClaimsIdentity now has methods to query the claims collection, e.g. HasClaim(), FindFirst(), FindAll(). ClaimsPrincipal has those methods as well. But they work across all contained identities. Nice! ClaimsPrincipal.Current retrieves the ClaimsPrincipal from Thread.CurrentPrincipal. Combined with the above changes, no casting necessary anymore. SecurityTokenHandler now has read and write methods that work directly with strings. This makes it much easier to deal with non-XML tokens like SWT or JWT. A new session security token handler that uses the ASP.NET machine key to protect the cookie. This makes it easier to get started in web farm scenarios. No need for a custom service host factory or the federation behavior anymore. WCF can be switched into “WIF mode” with the useIdentityConfiguration switch (odd name though). Tooling has become better and the new test STS makes it very easy to get started. On the other hand – and that was kind of expected – to bring claims into the core framework, there are also some breaking changes for WIF code. If you want to migrate (and I would recommend that), most changes to your code are mechanical. The following is a brain dump of the changes I encountered. Assembly Microsoft.IdentityModel is gone. The new functionality is now in mscorlib, System.IdentityModel(.Services) and System.ServiceModel. All the namespaces have changed as well. No IClaimsPrincipal and IClaimsIdentity anymore. Configuration section has been split into <system.identityModel /> and <system.identityModel.services />. WCF configuration story has changed as well. Claim.ClaimType is now Claim.Type. ClaimCollection is now IEnumerable<Claim>. IsSessionMode is now IsReferenceMode. Bootstrap token handling is different now. ClaimsPrincipalHttpModule is gone. This is not really needed anymore, apart from maybe claims transformation (see here). Various factory methods on ClaimsPrincipal are gone (e.g. ClaimsPrincipal.CreateFromIdentity()). SecurityTokenHandler.ValidateToken now returns a ReadOnlyCollection<ClaimsIdentity>. Some lower level helper classes are gone or internal now (e.g. KeyGenerator). The WCF WS-Trust bindings are gone. I think this is a pity. They were *really* useful when doing work with WSTrustChannelFactory. Since WIF is part of the Windows operating system and also supported in future versions of .NET, there is no urgent need to migrate to the 4.5 claims model. But obviously, going forward, at some point you want to make the move.

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• Play in NetBeans IDE (Part 2)

  - by Geertjan

  Peter Hilton was one of many nice people I met for the first time during the last few days constituting JAX London. He did a session today on the Play framework which, if I understand it correctly, is an HTML5 framework. It doesn't use web.xml, Java EE, etc. It uses Scala internally, as well as in its templating language.  Support for Play would, I guess, based on the little I know about it right now, consist of extending the HTML5 application project, which is new in NetBeans IDE 7.3. The workflow I imagine goes as follows. You'd create a new HTML5 application project, at which point you can choose a variety of frameworks and templates (Coffee Script, Angular, etc), which comes out of the box with the HTML5 support (i.e., Project Easel) in NetBeans IDE 7.3. Then, once the project is created, you'll right-click it and go to the Project Properties dialog, where you'll be able to enable Play support: At this stage, i.e., when you've checked the checkbox above and then clicked OK, all the necessary Play files will be added to your project, e.g., the routes file and the application.conf, for example. And then you have a Play application. Creating support in this way entails nothing more than creating a module that looks like this, i.e., with one Java class, where even the layer.xml file below is superfluous: All the code in the PlayEnablerPlanel.java that you see above is as follows: import java.awt.BorderLayout; import javax.swing.JCheckBox; import javax.swing.JComponent; import javax.swing.JPanel; import org.netbeans.spi.project.ui.support.ProjectCustomizer; import org.netbeans.spi.project.ui.support.ProjectCustomizer.Category; import org.openide.util.Lookup; public class PlayEnablerPanel implements ProjectCustomizer.CompositeCategoryProvider {     @ProjectCustomizer.CompositeCategoryProvider.Registration(             projectType = "org.netbeans.modules.web.clientproject",             position = 1000)     public static PlayEnablerPanel enablePlay() {         return new PlayEnablerPanel();     }     @Override     public Category createCategory(Lookup lkp) {         return ProjectCustomizer.Category.create("Play Framework", "Configure Play", null);     }     @Override     public JComponent createComponent(Category ctgr, Lookup lkp) {         JPanel playPanel = new JPanel(new BorderLayout());         playPanel.add(new JCheckBox("Enable Play"), BorderLayout.NORTH);         return playPanel;     } } Looking forward to having a beer with Peter soon (he lives not far away, in Rotterdam) to discuss this! Also read Part 1 of this series, which I wrote some time ago, and which has other ideas and considerations.

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• Is the Leptonica implementation of 'Modified Median Cut' not using the median at all?

  - by TheCodeJunkie

  I'm playing around a bit with image processing and decided to read up on how color quantization worked and after a bit of reading I found the Modified Median Cut Quantization algorithm. I've been reading the code of the C implementation in Leptonica library and came across something I thought was a bit odd. Now I want to stress that I am far from an expert in this area, not am I a math-head, so I am predicting that this all comes down to me not understanding all of it and not that the implementation of the algorithm is wrong at all. The algorithm states that the vbox should be split along the lagest axis and that it should be split using the following logic The largest axis is divided by locating the bin with the median pixel (by population), selecting the longer side, and dividing in the center of that side. We could have simply put the bin with the median pixel in the shorter side, but in the early stages of subdivision, this tends to put low density clusters (that are not considered in the subdivision) in the same vbox as part of a high density cluster that will outvote it in median vbox color, even with future median-based subdivisions. The algorithm used here is particularly important in early subdivisions, and 3is useful for giving visible but low population color clusters their own vbox. This has little effect on the subdivision of high density clusters, which ultimately will have roughly equal population in their vboxes. For the sake of the argument, let's assume that we have a vbox that we are in the process of splitting and that the red axis is the largest. In the Leptonica algorithm, on line 01297, the code appears to do the following Iterate over all the possible green and blue variations of the red color For each iteration it adds to the total number of pixels (population) it's found along the red axis For each red color it sum up the population of the current red and the previous ones, thus storing an accumulated value, for each red note: when I say 'red' I mean each point along the axis that is covered by the iteration, the actual color may not be red but contains a certain amount of red So for the sake of illustration, assume we have 9 "bins" along the red axis and that they have the following populations 4 8 20 16 1 9 12 8 8 After the iteration of all red bins, the partialsum array will contain the following count for the bins mentioned above 4 12 32 48 49 58 70 78 86 And total would have a value of 86 Once that's done it's time to perform the actual median cut and for the red axis this is performed on line 01346 It iterates over bins and check they accumulated sum. And here's the part that throws me of from the description of the algorithm. It looks for the first bin that has a value that is greater than total/2 Wouldn't total/2 mean that it is looking for a bin that has a value that is greater than the average value and not the median ? The median for the above bins would be 49 The use of 43 or 49 could potentially have a huge impact on how the boxes are split, even though the algorithm then proceeds by moving to the center of the larger side of where the matched value was.. Another thing that puzzles me a bit is that the paper specified that the bin with the median value should be located, but does not mention how to proceed if there are an even number of bins.. the median would be the result of (a+b)/2 and it's not guaranteed that any of the bins contains that population count. So this is what makes me thing that there are some approximations going on that are negligible because of how the split actually takes part at the center of the larger side of the selected bin. Sorry if it got a bit long winded, but I wanted to be as thoroughas I could because it's been driving me nuts for a couple of days now ;)

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• F# Objects &ndash; Integration with the other .Net Languages &ndash; Part 2

  - by MarkPearl

  So in part one of my posting I covered the real basics of object creation. Today I will hopefully dig a little deeper… My expert F# book brings up an interesting point – properties in F# are just syntactic sugar for method calls. This makes sense… for instance assume I had the following object with the property exposed called Firstname. type Person(Firstname : string, Lastname : string) = member v.Firstname = Firstname I could extend the Firstname property with the following code and everything would be hunky dory… type Person(Firstname : string, Lastname : string) = member v.Firstname = Console.WriteLine("Side Effect") Firstname   All that this would do is each time I use the property Firstname, I would see the side effect printed to the screen saying “Side Effect”. Member methods have a very similar look & feel to properties, in fact the only difference really is that you declare that parameters are being passed in. type Person(Firstname : string, Lastname : string) = member v.FullName(middleName) = Firstname + " " + middleName + " " + Lastname   In the code above, FullName requires the parameter middleName, and if viewed from another project in C# would show as a method and not a property. Precomputation Optimizations Okay, so something that is obvious once you think of it but that poses an interesting side effect of mutable value holders is pre-computation of results. All it is, is a slight difference in code but can result in quite a huge saving in performance. Basically pre-computation means you would not need to compute a value every time a method is called – but could perform the computation at the creation of the object (I hope I have got it right). In a way I battle to differentiate this from lazy evaluation but I will show an example to explain the principle. Let me try and show an example to illustrate the principle… assume the following F# module namespace myNamespace open System module myMod = let Add val1 val2 = Console.WriteLine("Compute") val1 + val2 type MathPrecompute(val1 : int, val2 : int) = let precomputedsum = Add val1 val2 member v.Sum = precomputedsum type MathNormalCompute(val1 : int, val2 : int) = member v.Sum = Add val1 val2 Now assume you have a C# console app that makes use of the objects with code similar to the following… using System; using myNamespace; namespace CSharpTest { class Program { static void Main(string[] args) { Console.WriteLine("Constructing Objects"); var myObj1 = new myMod.MathNormalCompute(10, 11); var myObj2 = new myMod.MathPrecompute(10, 11); Console.WriteLine(""); Console.WriteLine("Normal Compute Sum..."); Console.WriteLine(myObj1.Sum); Console.WriteLine(myObj1.Sum); Console.WriteLine(myObj1.Sum); Console.WriteLine(""); Console.WriteLine("Pre Compute Sum..."); Console.WriteLine(myObj2.Sum); Console.WriteLine(myObj2.Sum); Console.WriteLine(myObj2.Sum); Console.ReadKey(); } } } The output when running the console application would be as follows…. You will notice with the normal compute object that the system would call the Add function every time the method was called. With the Precompute object it only called the compute method when the object was created. Subtle, but something that could lead to major performance benefits. So… this post has gone off in a slight tangent but still related to F# objects.

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• SSI: Failed String Comparison with CGI Environment Variable [migrated]

  - by Calyo Delphi

  I am currently working on developing a personal website. It's not my first time doing this, but this is my first major foray into implementing SSI. I've run myself into a wall, however, with an if-else directive that uses one of the CGI environment variables as part of its comparison. Even after some limited attempts at debugging, all of the output and documentation that I have means that the comparisons being made should fail outright. This is not the case, and the wrong evaluation is being made by the if-else directive. Here's the code in the file index.shtml: <head> <!--#set var="page" value="Home" --> <!--#include file="headlinks.shtml" --> <style> img#ref { float: right; margin-left: 8px; border-width: 0px; } </style> </head> Here's the code in the file headlinks.shtml: <title><!--#echo var="page" --> &ndash; <!--#echo var="HTTP_HOST" --></title> <!--#set var="docroot" value="${DOCUMENT_ROOT}" --> <!--#echo var="docroot" --> <!--#if expr="( $docroot != '/Applications/MAMP/htdocs' ) || ( $docroot != '/home/dragarch/public_html' )" --> <link rel="stylesheet" type="text/css" href="../style.css"> <link rel="shortcut icon" type="image/svg+xml" href="../favicon.svg" /> <!--#else --> <link rel="stylesheet" type="text/css" href="style.css"> <link rel="shortcut icon" type="image/svg+xml" href="favicon.svg" /> <!--#endif --> And here's the output for the file index.shtml: <title>Home &ndash; dragarch</title> /Applications/MAMP/htdocs <link rel="stylesheet" type="text/css" href="../style.css"> <link rel="shortcut icon" type="image/svg+xml" href="../favicon.svg" /> Both style.css and favicon.svg are in the document root with index.shtml, so the if directive should fail and default to the output of the else directive. As you can see, while the document root (which is currently the MAMP htdocs folder on my own notebook) is correct according to the output of the echo directive, the comparison in the if-else directive fails to compare the strings properly. I'm using this page for my documentation: http://httpd.apache.org/docs/2.2/mod/mod_include.html I'm at a complete loss as to why this is the case, and need a bit of help here. EDIT: I should note that dragarch is a hostname that I configured in /etc/hosts to point to 127.0.0.1 so I could test the site without having to use localhost. It has no real effect on the functionality of anything, other than to just act as a prettier hostname to use.

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• How do you go from a so so programmer to a great one? [closed]

  - by Cervo

  How do you go from being an okay programmer to being able to write maintainable clean code? For example David Hansson was writing Basecamp when in the process he created Rails as part of writing Basecamp in a clean/maintainable way. But how do you know when there is value in a side project like that? I have a bachelors in computer science, and I am about to get a masters and I will say that colleges teach you to write code to solve problems, not neatly or anything. Basically you think of a problem, come up with a solution, and write it down...not necessarily the most maintainable way in the world. Also my first job was in a startup, and now my third is in a small team in a large company where the attitude was/is get it done yesterday (also most of my jobs are mainly database development with SQL with a few ASP.NET web pages/.NET apps on the side). So of course cut/paste is more favored than making things more cleanly. And they would rather have something yesterday even if you have to rewrite it next month rather than to have something in a week that lasts for a year. Also spaghetti code turns up all over the place, and it takes very smart people to write/understand/maintain spaghetti code...However it would be better to do things so simple/clean that even a caveman/woman could do maintenance. Also I get very bored/unmotivated having to go modify the same things cut/pasted in a few locations. Is this the type of skill that you need to learn by working with a serious software organization that has an emphasis on maintenance and maybe even an architect who designs a system architecture and reviews code? Could you really learn it by volunteering on an open source project (it seems to me that a full time programmer job is way more practice than a few hours a week on an open source project)? Is there some course where you can learn this? I can attest that graduate school and undergraduate school do not really emphasize clean software at all. They just teach the structures/algorithms and then send you off into the world to solve problems. Overall I think the first thing is learning to write clean/maintainable code within the bounds of the project in order to become a good programmer. Then the next thing is learning when you need to do a side project (like a framework) to make things more maintainable/clean even while you still deliver things for the deadline in order to become a great programmer. For example, you are making an SQL report and someone gives you 100 calculations for individual columns. At what point does it make sense to construct a domain specific language to encode the rules in simply and then generate all the SQL as opposed to cut/pasting the query from the table a bunch of times and then adjusting each query to do the appropriate calculations. This is the type of thing I would say a great programmer would know. He/she would maybe even know ways to avoid the domain specific language and to still do all the calculations without creating an unmaintainable mess or a ton of repetitive code to cut/paste everywhere.

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• Slide 2d Vector to destination over a period of time

  - by SchautDollar

  I am making a library of GUI controls for games I make with XNA. I am currently developing the library as I make a game so I can test the features and find errors/bugs and hopefully smash them right away. My current issue is on a slide feature I want to implement for my base class that all controls inherit. My goal is to get the control to slide to a specified point over a specified amount of time. Here is the #region containing the code #region Slide private bool sliding; private Vector2 endPoint; private float slideTimeLeft; private float speed; private bool wasEnabled; private Vector2 slideDirection; private float slideDistance; public void Slide(Vector2 startPoint, Vector2 endPoint, float slideTime) { this.location = startPoint; Slide(endPoint,slideTime); } public void Slide(Vector2 endPoint, float slideTime) { this.wasEnabled = this.enabled; this.enabled = false; this.sliding = true; Vector2 tempLength = endPoint - this.location; this.slideDistance = tempLength.Length(); //Was this.slideDistance = (float)Math.Sqrt(tempLength.LengthSquared()); this.speed = slideTime / this.slideDistance; this.endPoint = endPoint; this.slideTimeLeft = slideTime; } private void UpdateSlide(GameTime gameTime) { if (this.sliding) { this.slideTimeLeft -= gameTime.ElapsedGameTime.Milliseconds; if (this.slideTimeLeft >= 0 ) { if ((this.endPoint-this.location).Length() != 0){//Was if (this.endPoint.LengthSquared() > 0 || this.location.LengthSquared() > 0) { this.slideDirection = Vector2.Normalize(this.endPoint - this.location); } this.location += this.slideDirection * speed * gameTime.ElapsedGameTime.Milliseconds;//This is where I believe the issue is, but I'm not sure. It seems right to me... (Even though it doesn't work) } else { this.enabled = this.wasEnabled; this.location = this.endPoint;//After time, the controls position will get set to be the endpoint. this.sliding = false; } } } #endregion this.location is the location of the control elsewhere defined in the class. I have looked at this blog as a huge reference and have googled around quite and have looked on many forums but can't find anything that shows how to implement it. Please and Thanks for your time! EDIT: I have switched this line "this.location += this.slideDirection * speed * gameTime.ElapsedGameTime.Milliseconds;" several times to see what it does. My issue is getting the control to smoothly move to the end location. It moves after the time has expired, but It doesn't move other then that except flash in my face. EDIT2: I have used the first slide method with 3 parameters and it works except it doesn't do it in a period of time and once it gets to its destination, it starts moving randomly towards the previous location and the end location.

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• ???????,???????????

  - by ??-Oracle

  Normal 0 7.8 ? 0 2 false false false EN-US ZH-CN X-NONE ??: 1.???????; 2.??????????????????; 3.????????????????,??????????,????????; ??: ?????????: SQL> create table test_b (id number(10)) tablespace bbb; Table created. SQL> insert into test_b values (1); 1 row created. SQL> commit; NAME --------------------------------------------------------------------------------     FILE# ---------- /opt/oracle/oradata/R11203/aaa.dbf        10 /opt/oracle/oradata/R11203/bbb.dbf        11 11 rows selected. SQL> host ??????,?????? bash-4.2$ ls -al /opt/oracle/oradata/R11203/bbb.dbf -rw-rw----   1 oracle     dba        10493952 Apr  4 09:53 /opt/oracle/oradata/R11203/bbb.dbf bash-4.2$ mv /opt/oracle/oradata/R11203/bbb.dbf /opt/oracle/oradata/R11203/bbb.dbf.bak bash-4.2$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.3.0 Production on Fri Apr 4 09:55:03 2014 Copyright (c) 1982, 2011, Oracle.  All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options SQL> alter tablespace bbb read only; alter tablespace bbb read only * ERROR at line 1: ORA-01116: error in opening database file 11 ORA-01110: data file 11: '/opt/oracle/oradata/R11203/bbb.dbf' ORA-27041: unable to open file HPUX-ia64 Error: 2: No such file or directory Additional information: 3 SQL> shutdown immediate; ORA-01116: error in opening database file 11 ORA-01110: data file 11: '/opt/oracle/oradata/R11203/bbb.dbf' ORA-27041: unable to open file HPUX-ia64 Error: 2: No such file or directory Additional information: 3 SQL> select status from v$instance; STATUS ------------ OPEN SQL> alter system switch logfile; System altered. SQL> / System altered. SQL> / System altered. SQL>/ System altered. SQL> / System altered. SQL> / System altered. SQL> ?? SQL> shutdown immediate; ORA-01116: error in opening database file 11 ORA-01110: data file 11: '/opt/oracle/oradata/R11203/bbb.dbf' ORA-27041: unable to open file HPUX-ia64 Error: 2: No such file or directory Additional information: 3 SQL> shutdown abort; ORACLE instance shut down. ???????mount?? SQL> startup mount; ORACLE instance started. Total System Global Area  329859072 bytes Fixed Size                  2182336 bytes Variable Size             285213504 bytes Database Buffers           37748736 bytes Redo Buffers                4714496 bytes Database mounted. ??alter database create datafile <> as ....???,???????????: SQL> alter database create datafile 11; Database altered. ???????redo log????????? SQL> recover datafile 11; Media recovery complete. SQL> alter database open; Database altered. SQL> select * from test_b;        ID ----------         1 DefSemiHidden="true" DefQFormat="false" DefPriority="99" LatentStyleCount="267" UnhideWhenUsed="false" QFormat="true" Name="Normal"/ UnhideWhenUsed="false" QFormat="true" Name="heading 1"/ UnhideWhenUsed="false" QFormat="true" Name="Title"/ UnhideWhenUsed="false" QFormat="true" Name="Subtitle"/ UnhideWhenUsed="false" QFormat="true" Name="Strong"/ UnhideWhenUsed="false" QFormat="true" Name="Emphasis"/ UnhideWhenUsed="false" Name="Table Grid"/ UnhideWhenUsed="false" QFormat="true" Name="No Spacing"/ UnhideWhenUsed="false" Name="Light Shading"/ UnhideWhenUsed="false" Name="Light List"/ UnhideWhenUsed="false" Name="Light Grid"/ UnhideWhenUsed="false" Name="Medium Shading 1"/ UnhideWhenUsed="false" Name="Medium Shading 2"/ UnhideWhenUsed="false" Name="Medium List 1"/ UnhideWhenUsed="false" Name="Medium List 2"/ UnhideWhenUsed="false" Name="Medium Grid 1"/ UnhideWhenUsed="false" Name="Medium Grid 2"/ UnhideWhenUsed="false" Name="Medium Grid 3"/ UnhideWhenUsed="false" Name="Dark List"/ UnhideWhenUsed="false" Name="Colorful Shading"/ UnhideWhenUsed="false" Name="Colorful List"/ UnhideWhenUsed="false" Name="Colorful Grid"/ UnhideWhenUsed="false" Name="Light Shading Accent 1"/ UnhideWhenUsed="false" Name="Light List Accent 1"/ UnhideWhenUsed="false" Name="Light Grid Accent 1"/ UnhideWhenUsed="false" Name="Medium Shading 1 Accent 1"/ UnhideWhenUsed="false" Name="Medium Shading 2 Accent 1"/ UnhideWhenUsed="false" Name="Medium List 1 Accent 1"/ UnhideWhenUsed="false" QFormat="true" Name="List Paragraph"/ UnhideWhenUsed="false" QFormat="true" Name="Quote"/ UnhideWhenUsed="false" QFormat="true" Name="Intense Quote"/ UnhideWhenUsed="false" Name="Medium List 2 Accent 1"/ UnhideWhenUsed="false" Name="Medium Grid 1 Accent 1"/ UnhideWhenUsed="false" Name="Medium Grid 2 Accent 1"/ UnhideWhenUsed="false" Name="Medium Grid 3 Accent 1"/ UnhideWhenUsed="false" Name="Dark List Accent 1"/ UnhideWhenUsed="false" Name="Colorful Shading Accent 1"/ UnhideWhenUsed="false" Name="Colorful List Accent 1"/ UnhideWhenUsed="false" Name="Colorful Grid Accent 1"/ UnhideWhenUsed="false" Name="Light Shading Accent 2"/ UnhideWhenUsed="false" Name="Light List Accent 2"/ UnhideWhenUsed="false" Name="Light Grid Accent 2"/ UnhideWhenUsed="false" Name="Medium Shading 1 Accent 2"/ UnhideWhenUsed="false" Name="Medium Shading 2 Accent 2"/ UnhideWhenUsed="false" Name="Medium List 1 Accent 2"/ UnhideWhenUsed="false" Name="Medium List 2 Accent 2"/ UnhideWhenUsed="false" Name="Medium Grid 1 Accent 2"/ UnhideWhenUsed="false" Name="Medium Grid 2 Accent 2"/ UnhideWhenUsed="false" Name="Medium Grid 3 Accent 2"/ UnhideWhenUsed="false" Name="Dark List Accent 2"/ UnhideWhenUsed="false" Name="Colorful Shading Accent 2"/ UnhideWhenUsed="false" Name="Colorful List Accent 2"/ UnhideWhenUsed="false" Name="Colorful Grid Accent 2"/ UnhideWhenUsed="false" Name="Light Shading Accent 3"/ UnhideWhenUsed="false" Name="Light List Accent 3"/ UnhideWhenUsed="false" Name="Light Grid Accent 3"/ UnhideWhenUsed="false" Name="Medium Shading 1 Accent 3"/ UnhideWhenUsed="false" Name="Medium Shading 2 Accent 3"/ UnhideWhenUsed="false" Name="Medium List 1 Accent 3"/ UnhideWhenUsed="false" Name="Medium List 2 Accent 3"/ UnhideWhenUsed="false" Name="Medium Grid 1 Accent 3"/ UnhideWhenUsed="false" Name="Medium Grid 2 Accent 3"/ UnhideWhenUsed="false" Name="Medium Grid 3 Accent 3"/ UnhideWhenUsed="false" Name="Dark List Accent 3"/ UnhideWhenUsed="false" Name="Colorful Shading Accent 3"/ UnhideWhenUsed="false" Name="Colorful List Accent 3"/ UnhideWhenUsed="false" Name="Colorful Grid Accent 3"/ UnhideWhenUsed="false" Name="Light Shading Accent 4"/ UnhideWhenUsed="false" Name="Light List Accent 4"/ UnhideWhenUsed="false" Name="Light Grid Accent 4"/ UnhideWhenUsed="false" Name="Medium Shading 1 Accent 4"/ UnhideWhenUsed="false" Name="Medium Shading 2 Accent 4"/ UnhideWhenUsed="false" Name="Medium List 1 Accent 4"/ UnhideWhenUsed="false" Name="Medium List 2 Accent 4"/ UnhideWhenUsed="false" Name="Medium Grid 1 Accent 4"/ UnhideWhenUsed="false" Name="Medium Grid 2 Accent 4"/ UnhideWhenUsed="false" Name="Medium Grid 3 Accent 4"/ UnhideWhenUsed="false" Name="Dark List Accent 4"/ UnhideWhenUsed="false" Name="Colorful Shading Accent 4"/ UnhideWhenUsed="false" Name="Colorful List Accent 4"/ UnhideWhenUsed="false" Name="Colorful Grid Accent 4"/ UnhideWhenUsed="false" Name="Light Shading Accent 5"/ UnhideWhenUsed="false" Name="Light List Accent 5"/ UnhideWhenUsed="false" Name="Light Grid Accent 5"/ UnhideWhenUsed="false" Name="Medium Shading 1 Accent 5"/ UnhideWhenUsed="false" Name="Medium Shading 2 Accent 5"/ UnhideWhenUsed="false" Name="Medium List 1 Accent 5"/ UnhideWhenUsed="false" Name="Medium List 2 Accent 5"/ UnhideWhenUsed="false" Name="Medium Grid 1 Accent 5"/ UnhideWhenUsed="false" Name="Medium Grid 2 Accent 5"/ UnhideWhenUsed="false" Name="Medium Grid 3 Accent 5"/ UnhideWhenUsed="false" Name="Dark List Accent 5"/ UnhideWhenUsed="false" Name="Colorful Shading Accent 5"/ UnhideWhenUsed="false" Name="Colorful List Accent 5"/ UnhideWhenUsed="false" Name="Colorful Grid Accent 5"/ UnhideWhenUsed="false" Name="Light Shading Accent 6"/ UnhideWhenUsed="false" Name="Light List Accent 6"/ UnhideWhenUsed="false" Name="Light Grid Accent 6"/ UnhideWhenUsed="false" Name="Medium Shading 1 Accent 6"/ UnhideWhenUsed="false" Name="Medium Shading 2 Accent 6"/ UnhideWhenUsed="false" Name="Medium List 1 Accent 6"/ UnhideWhenUsed="false" Name="Medium List 2 Accent 6"/ UnhideWhenUsed="false" Name="Medium Grid 1 Accent 6"/ UnhideWhenUsed="false" Name="Medium Grid 2 Accent 6"/ UnhideWhenUsed="false" Name="Medium Grid 3 Accent 6"/ UnhideWhenUsed="false" Name="Dark List Accent 6"/ UnhideWhenUsed="false" Name="Colorful Shading Accent 6"/ UnhideWhenUsed="false" Name="Colorful List Accent 6"/ UnhideWhenUsed="false" Name="Colorful Grid Accent 6"/ UnhideWhenUsed="false" QFormat="true" Name="Subtle Emphasis"/ UnhideWhenUsed="false" QFormat="true" Name="Intense Emphasis"/ UnhideWhenUsed="false" QFormat="true" Name="Subtle Reference"/ UnhideWhenUsed="false" QFormat="true" Name="Intense Reference"/ UnhideWhenUsed="false" QFormat="true" Name="Book Title"/ /* Style Definitions */ table.MsoNormalTable {mso-style-name:????; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.5pt; mso-bidi-font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-font-kerning:1.0pt;}

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• ??OPEN CURSOR?BULK COLLECT

  - by Liu Maclean(???)

  ????T.askmaclean.com?????bulk collect?open cursor???, ?????????  ??????: ???? OPEN_CURSOR ????SQL?? ???????. ?????? ????? ???????????????? ????? test_soruce create table zengfankun_temp01 as select * from dba_objects;select count(*) from zengfankun_temp01;–12,6826analyze table zengfankun_temp01 compute statistics; create or replace procedure test_open_cursor istype type_owner is table of zengfankun_temp01.owner%type index by binary_integer;type type_object_name is table of zengfankun_temp01.object_name%type index by binary_integer;type type_object_id is table of zengfankun_temp01.object_id%type index by binary_integer;type type_object_type is table of zengfankun_temp01.object_type%type index by binary_integer;type type_last_ddl_time is table of zengfankun_temp01.last_ddl_time%type index by binary_integer; l_ary_owner type_owner;l_ary_object_name type_object_name;l_ary_object_id type_object_id;l_ary_object_type type_object_type;l_ary_last_ddl_time type_last_ddl_time; cursor cur_object isselect owner,object_name,object_id,object_type,last_ddl_timefrom zengfankun_temp01order by owner,object_name,object_type,last_ddl_time;OPEN_START number;OPEN_END number;FETCH_START number;FETCH_END number;beginDBMS_OUTPUT.ENABLE (buffer_size=>null) ;OPEN_START:=dbms_utility.get_time();open cur_object;OPEN_END :=dbms_utility.get_time();dbms_output.put_line(‘OPEN_TIME:’||TO_CHAR(OPEN_END-OPEN_START));loopFETCH_START:=dbms_utility.get_time();fetch cur_object bulk collect intol_ary_owner,l_ary_object_name,l_ary_object_id,l_ary_object_type,l_ary_last_ddl_timelimit 10000;FETCH_END:=dbms_utility.get_time();dbms_output.put_line(‘FETCH_TIME:’||TO_CHAR(FETCH_END-FETCH_START)||’ ROWCOUNT:’||cur_object%rowCount); exit when cur_object%notfound or cur_object%notfound is null;end loop;end test_open_cursor; OPEN_TIME:12FETCH_TIME:21 ROWCOUNT:10000FETCH_TIME:3 ROWCOUNT:20000FETCH_TIME:3 ROWCOUNT:30000FETCH_TIME:3 ROWCOUNT:40000FETCH_TIME:3 ROWCOUNT:50000FETCH_TIME:3 ROWCOUNT:60000FETCH_TIME:3 ROWCOUNT:70000FETCH_TIME:3 ROWCOUNT:80000FETCH_TIME:3 ROWCOUNT:90000FETCH_TIME:3 ROWCOUNT:100000FETCH_TIME:3 ROWCOUNT:110000FETCH_TIME:3 ROWCOUNT:120000FETCH_TIME:1 ROWCOUNT:126826 ???? OPEN_TIME:0FETCH_TIME:18 ROWCOUNT:10000FETCH_TIME:3 ROWCOUNT:20000FETCH_TIME:3 ROWCOUNT:30000FETCH_TIME:3 ROWCOUNT:40000FETCH_TIME:3 ROWCOUNT:50000FETCH_TIME:3 ROWCOUNT:60000FETCH_TIME:3 ROWCOUNT:70000FETCH_TIME:3 ROWCOUNT:80000FETCH_TIME:3 ROWCOUNT:90000FETCH_TIME:3 ROWCOUNT:100000FETCH_TIME:3 ROWCOUNT:110000FETCH_TIME:3 ROWCOUNT:120000FETCH_TIME:2 ROWCOUNT:126826 SQL?????????, ????????????.??OPEN CURSOR ????0???????????3??.??N? ??????. ???? ?N? ?????????? ??????. ??????????????? ??????????. ?????????10000??? ???????????????????clear???, ???????????: ?OPEN CURSOR ?????, PL/SQL????SQL????PARSE SQL????????, ??????OPEN CURSOR????SNAPSHOT SCN ??SCN, ??Oracle?????FETCH?????,???????????????? ????FETCH ??????????????,???????Current Block, The most recent version of block , ?????SCN >> Snapshot scn, ????UNDO???? ???SCN ???Best Block ,???Read Consistentcy;???? ???UNDO SNAPSHOT???????????????Best Block??,???????ORA-1555??? ????????, ??????????,???????????????char(2000)????, ???????????????,????bulk collect fetch??fetch 10 ???,????????OPEN CURSOR?????PARSE??SQL????????, ??????????fetch bulk collect??????????10????,??”_trace_pin_time”????Server Process?pin CR block???,??????????Fetch Bulk Collect limit 10??10?buffer?pin? [oracle@nas ~]$ sqlplus / as sysdba SQL*Plus: Release 11.2.0.3.0 Production on Wed Aug 1 11:36:52 2012 Copyright (c) 1982, 2011, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production With the Partitioning, OLAP, Data Mining and Real Application Testing options SQL> select * from global_name; GLOBAL_NAME -------------------------------------------------------------------------------- http://www.askmaclean.com SQL> create table maclean (t1 char(2000)) tablespace users pctfree 99; Table created. SQL> begin 2 for i in 1..200 loop 3 insert into maclean values('MACLEAN'); 4 commit ; 5 end loop; 6 end; 7 / PL/SQL procedure successfully completed. SQL> exec dbms_stats.gather_table_stats('','MACLEAN'); PL/SQL procedure successfully completed. SQL> select count(*) from maclean; COUNT(*) ---------- 200 SQL> select blocks,num_rows from dba_tables where table_name='MACLEAN'; BLOCKS NUM_ROWS ---------- ---------- 244 200 SQL> alter system set "_trace_pin_time"=1 scope=spfile; System altered. SQL> startup force; ORACLE instance started. Total System Global Area 3140026368 bytes Fixed Size 2232472 bytes Variable Size 1795166056 bytes Database Buffers 1325400064 bytes Redo Buffers 17227776 bytes Database mounted. Database opened. SQL> alter session set events '10046 trace name context forever,level 12'; Session altered. SQL> SQL> SQL> declare 2 cursor v_cursor is 3 select * from sys.maclean; 4 type v_type is table of sys.maclean%rowtype index by binary_integer; 5 rec_tab v_type; 6 begin 7 open v_cursor; 8 dbms_lock.sleep(30); 9 loop 10 fetch v_cursor bulk collect 11 into rec_tab limit 10; 12 dbms_lock.sleep(10); 13 exit when v_cursor%notfound; 14 end loop; 15 end; 16 / ?????10046 trace+ pin trace: PARSING IN CURSOR #47499559136872 len=337 dep=0 uid=0 oct=47 lid=0 tim=1343836146412056 hv=496860239 ad='11a11dbb0' sqlid='4zh7954ftuz2g' declare cursor v_cursor is select * from sys.maclean; type v_type is table of sys.maclean%rowtype index by binary_integer; rec_tab v_type; begin open v_cursor; dbms_lock.sleep(30); loop fetch v_cursor bulk collect into rec_tab limit 10; dbms_lock.sleep(10); exit when v_cursor%notfound; end loop; end; END OF STMT PARSE #47499559136872:c=0,e=346,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=0,tim=1343836146412051 ===================== PARSING IN CURSOR #47499559126280 len=25 dep=1 uid=0 oct=3 lid=0 tim=1343836146414939 hv=3296884535 ad='11a11d250' sqlid='2mb1493284xtr' SELECT * FROM SYS.MACLEAN END OF STMT PARSE #47499559126280:c=1999,e=2427,p=0,cr=0,cu=0,mis=1,r=0,dep=1,og=1,plh=2568761675,tim=1343836146414937 EXEC #47499559126280:c=0,e=55,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=1,plh=2568761675,tim=1343836146415104 ????? ? SELECT * FROM SYS.MACLEAN? PARSE ????? , ????FETCH???????pin ????????, ????OPEN CURSOR????? *** 2012-08-01 11:49:36.424 WAIT #47499559136872: nam='PL/SQL lock timer' ela= 30009361 duration=0 p2=0 p3=0 obj#=-1 tim=1343836176424782 ???30s pin ktewh26: kteinpscan dba 0x10a6202:4 time 1039048805 pin ktewh27: kteinmap dba 0x10a6202:4 time 1039048847 pin kdswh11: kdst_fetch dba 0x10a6203:1 time 1039048898 pin kdswh11: kdst_fetch dba 0x10a6204:1 time 1039048961 pin kdswh11: kdst_fetch dba 0x10a6205:1 time 1039049004 pin kdswh11: kdst_fetch dba 0x10a6206:1 time 1039049042 pin kdswh11: kdst_fetch dba 0x10a6207:1 time 1039049089 pin kdswh11: kdst_fetch dba 0x10a6208:1 time 1039049123 pin kdswh11: kdst_fetch dba 0x10a6209:1 time 1039049159 pin kdswh11: kdst_fetch dba 0x10a620a:1 time 1039049191 pin kdswh11: kdst_fetch dba 0x10a620b:1 time 1039049225 pin kdswh11: kdst_fetch dba 0x10a620c:1 time 1039049260 kdst_fetch???fetch??????? , ??fetch?10?? ???????FETCH FETCH #47499559126280:c=0,e=536,p=0,cr=12,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836176425542 *** 2012-08-01 11:49:46.428 WAIT #47499559136872: nam='PL/SQL lock timer' ela= 10002694 duration=0 p2=0 p3=0 obj#=-1 tim=134383618642829 ????10s pin kdswh11: kdst_fetch dba 0x10a620d:1 time 1049052211 pin kdswh11: kdst_fetch dba 0x10a620e:1 time 1049052264 pin kdswh11: kdst_fetch dba 0x10a620f:1 time 1049052299 pin kdswh11: kdst_fetch dba 0x10a6211:1 time 1049052332 pin kdswh11: kdst_fetch dba 0x10a6212:1 time 1049052364 pin kdswh11: kdst_fetch dba 0x10a6213:1 time 1049052398 pin kdswh11: kdst_fetch dba 0x10a6214:1 time 1049052430 pin kdswh11: kdst_fetch dba 0x10a6215:1 time 1049052462 pin kdswh11: kdst_fetch dba 0x10a6216:1 time 1049052494 pin kdswh11: kdst_fetch dba 0x10a6217:1 time 1049052525 FETCH #47499559126280:c=0,e=371,p=0,cr=10,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836186428807 ??pin 10????, ???fetch ?? WAIT #47499559136872: nam='PL/SQL lock timer' ela= 10002864 duration=0 p2=0 p3=0 obj#=-1 tim=1343836196431754 pin kdswh11: kdst_fetch dba 0x10a6218:1 time 1059055662 pin kdswh11: kdst_fetch dba 0x10a6219:1 time 1059055714 pin kdswh11: kdst_fetch dba 0x10a621a:1 time 1059055748 pin kdswh11: kdst_fetch dba 0x10a621b:1 time 1059055781 pin kdswh11: kdst_fetch dba 0x10a621c:1 time 1059055815 pin kdswh11: kdst_fetch dba 0x10a621d:1 time 1059055848 pin kdswh11: kdst_fetch dba 0x10a621e:1 time 1059055883 pin kdswh11: kdst_fetch dba 0x10a621f:1 time 1059055915 pin kdswh11: kdst_fetch dba 0x10a6221:1 time 1059055953 pin kdswh11: kdst_fetch dba 0x10a6222:1 time 1059055992 FETCH #47499559126280:c=0,e=385,p=0,cr=10,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836196432274 ???? ??????? DBA????? ............................ ???? WAIT #47499559136872: nam='PL/SQL lock timer' ela= 10002933 duration=0 p2=0 p3=0 obj#=-1 tim=1343836366495589 pin kdswh11: kdst_fetch dba 0x10a62f6:1 time 1229119497 pin kdswh11: kdst_fetch dba 0x10a62f7:1 time 1229119545 pin kdswh11: kdst_fetch dba 0x10a62f8:1 time 1229119576 pin kdswh11: kdst_fetch dba 0x10a62f9:1 time 1229119610 pin kdswh11: kdst_fetch dba 0x10a62fa:1 time 1229119644 pin kdswh11: kdst_fetch dba 0x10a62fb:1 time 1229119671 pin kdswh11: kdst_fetch dba 0x10a62fc:1 time 1229119703 pin kdswh11: kdst_fetch dba 0x10a62fd:1 time 1229119730 pin kdswh11: kdst_fetch dba 0x10a62fe:1 time 1229119760 pin kdswh11: kdst_fetch dba 0x10a62ff:1 time 1229119787 FETCH #47499559126280:c=0,e=340,p=0,cr=10,cu=0,mis=0,r=10,dep=1,og=1,plh=2568761675,tim=1343836366496067 ??????DBA? 0x10a6203 , ??DBA ? 0x10a62ff ???????DBA??MACLEAN????????,???DBA???Maclean????? getbfno?????dba??????????? CREATE OR REPLACE FUNCTION getbfno (p_dba IN VARCHAR2) RETURN VARCHAR2 IS l_str VARCHAR2 (255) DEFAULT NULL; l_fno VARCHAR2 (15); l_bno VARCHAR2 (15); BEGIN l_fno := DBMS_UTILITY.data_block_address_file (TO_NUMBER (LTRIM (p_dba, '0x'), 'xxxxxxxx' ) ); l_bno := DBMS_UTILITY.data_block_address_block (TO_NUMBER (LTRIM (p_dba, '0x'), 'xxxxxxxx' ) ); l_str := 'datafile# is:' || l_fno || CHR (10) || 'datablock is:' || l_bno || CHR (10) || 'dump command:alter system dump datafile ' || l_fno || ' block ' || l_bno || ';'; RETURN l_str; END; / Function created. SQL> select getbfno('0x10a6203') from dual; GETBFNO('0X10A6203') -------------------------------------------------------------------------------- datafile# is:4 datablock is:680451 dump command:alter system dump datafile 4 block 680451; SQL> select getbfno('0x10a62ff') from dual; GETBFNO('0X10A62FF') -------------------------------------------------------------------------------- datafile# is:4 datablock is:680703 dump command:alter system dump datafile 4 block 680703; SQL> select dbms_rowid.rowid_block_number(min(rowid)),dbms_rowid.rowid_relative_fno(min(rowid)) from maclean; DBMS_ROWID.ROWID_BLOCK_NUMBER(MIN(ROWID)) ----------------------------------------- DBMS_ROWID.ROWID_RELATIVE_FNO(MIN(ROWID)) ----------------------------------------- 680451 4 SQL> select dbms_rowid.rowid_block_number(max(rowid)),dbms_rowid.rowid_relative_fno(max(rowid)) from maclean; DBMS_ROWID.ROWID_BLOCK_NUMBER(MAX(ROWID)) ----------------------------------------- DBMS_ROWID.ROWID_RELATIVE_FNO(MAX(ROWID)) ----------------------------------------- 680703 4 ???????3???: 1.?OPEN CURSOR ?????, PL/SQL????SQL????PARSE SQL????????, ??????OPEN CURSOR????SNAPSHOT SCN ??SCN, ??Oracle?????FETCH?????,???????????????? 2.????FETCH ?????????????? 3. ???open cursor+ fetch bulk collect???”?????????”

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