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• EF Forced Concurrency Checks

  - by Imran

  Hi, I have an issue with EF 4.0 that I hope someone can help with. I currently have an entity that I want to update in a last in wins fashion (i.e. ignore concurrency checks and just overwrite whats in the db with what is submitted). It seems Entity Framework not only includes the primary key of the entity in the where clause of the generated sql, but also any foreign key fields. This is annoying as it means that I don't get true last in wins semantics and need to know what value the fk field had before the update or I get a concurrency exception. I am aware that this can be short circuited by including a foreign key field as well as the navigation property on the entity. I would like to avoid this if possible as it's not a very clean solution. I was just wondering if there was any other way to override this behaviour? It seems like more of a bug than a feature. I have no problem with ef doing concurrency checks if I instruct it to do so but not being able to bypass concurrency completely is a bit of a hindrance as there are many valid scenarios where this is not needed

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• Doxygen: grouping documentation by folder in a multi-project codebase

  - by John

  In one project, some pages were added - it was a new project in which doxygen was being tested properly - adding comments & pages - rather than simply auto-generating docs from our existing code-base. The problem is when doxygen is run on the main code-base, that project's pages show up at a top level. e.g they have a main-page and some sub-pages. But what we'd want is all those pages pushed down one level so you have main-project-main-project-pages. One question is what happens if multiple projects have a main-page? Do they get combined, or throw errors? Another question is if you can tell doxygen to use paths and containing folders to auto-generate groups or sections or page-hierarchies in some way? Going through all out projects to properly assign classes to groups is a mammoth task, so ideally everything in a directory would get put in a group of that name, as a way to make the documentation of non-doxygen codebases better. Sorry my question is a bit vague, the problem is even after reading the docs the terminology isn't totally clear yet. Hopefully the kind of question I'm asking is clear, if not I'll try to cobble an example file-structure together.

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• How do I combine two arrays in PHP based on a common key?

  - by Eoghan O'Brien

  Hi, I'm trying to join two associative arrays together based on an entry_id key. Both arrays come from individual database resources, the first stores entry titles, the second stores entry authors, the key=value pairs are as follows: array ( 'entry_id' => 1, 'title' => 'Test Entry' ) array ( 'entry_id' => 1, 'author_id' => 2 I'm trying to achieve an array structure like: array ( 'entry_id' => 1, 'author_id' => 2, 'title' => 'Test Entry' ) Currently, I've solved the problem by looping through each array and formatting the array the way I want, but I think this is a bit of a memory hog. $entriesArray = array(); foreach ($entryNames as $names) { foreach ($entryAuthors as $authors) { if ($names['entry_id'] === $authors['entry_id']) { $entriesArray[] = array( 'id' => $names['entry_id'], 'title' => $names['title'], 'author_id' => $authors['author_id'] ); } } } I'd like to know is there an easier, less memory intensive method of doing this?

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• NHibernate CreateSqlQuery and object graph

  - by magellings

  Hello I'm a newbie to NHibernate. I'd like to make one sql query to the database using joins to my three tables. I have an Application with many Roles with many Users. I'm trying to get NHibernate to properly form the object graph starting with the Application object. For example, if I have 10 application records, I want 10 application objects and then those objects have their roles which have their users. What I'm getting however resembles a Cartesian product in which I have as many Application objects as total User records. I've looked into this quite a bit and am not sure if it is possible to form the application hierarchy correctly. I can only get the flattened objects to come back. It seems "maybe" possible as in my research I've read about "grouped joins" and "hierarchical output" with an upcoming LINQ to NHibernate release. Again though I'm a newbie. [Update Based on Frans comment in Ayende's post here I'm guessing what I want to do is not possible http://ayende.com/Blog/archive/2008/12/01/solving-the-select-n1-problem.aspx ] Thanks for you time in advance. Session.CreateSQLQuery(@"SELECT a.ID, a.InternalName, r.ID, r.ApplicationID, r.Name, u.UserID, u.RoleID FROM dbo.[Application] a JOIN dbo.[Roles] r ON a.ID = r.ApplicationID JOIN dbo.[UserRoleXRef] u ON u.RoleID = r.ID") .AddEntity("app", typeof(RightsBasedSecurityApplication)) .AddJoin("role", "app.Roles") .AddJoin("user", "role.RightsUsers") .List<RightsBasedSecurityApplication>().AsQueryable();

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• How to handle refunds or rebates via a payment processor?

  - by Tai Squared

  I need to handle online payments and am trying to choose a payment processor. One requirement is to handle refunds and rebates to the customer. These won't always be at the time of sale, and not for the entire amount of the purchase. Is this something all payment processors handle? I don't want to have to do this manually as there may be many rebates, and they may be for relatively small amounts. I see PayPal has a refund API, but other parts of their site talk about sending a refund within 60 days. Is this something also required by the API? Amazon FPS also has a refund API that seems a bit more flexible. The Google Checkout refund has an amout field, but it's unclear to me if you can do a partial refund as the description reads "The refund-order command instructs Google Checkout to refund the buyer for a particular order." What are some things to look out for when looking for a payment processor that can handle rebates and refunds? Is there always a time limit in issuing these refunds? Is using a merchant account better for this type of process? I was hoping to avoid that due to the increased cost and complexity, but would consider it if it meets all of my requirements. Update It appears the refund process is fairly simple and handled by all processors. Is there any additional information on rebates? I would like to avoid a process of sending live checks to customers, but I will have to send rebates in some small amounts that may be a few months after the initial purchase.

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• Is F# a good language for card game AI?

  - by Anthony Brien

  I'm writing a Mahjong Game in C# (the Chinese traditional game, not the solitaire kind). While writing the code for the bot player's AI, I'm wondering if a functional language like F# would be a more suitable language than what I currently use which is C# with a lot of Linq. I don't know much about F# which is why I ask here. To illustrate what I try to solve, here's a quick summary of Mahjong: Mahjong plays a bit like Gin Rummy. You have 13 tiles in your hand, and each turn, you draw a tile and discard another one, trying to improve your hand towards a winning Mahjong hand, which consists or 4 sets and a pair. Sets can be a 3 of a kind (pungs), 4 of a kind (kongs) or a sequence of 3 consecutive tiles (chows). You can also steal another player's discard, if it can complete one of your sets. The code I had to write to detect if the bot can declare 3 consecutive tiles set (chow) is pretty tedious. I have to find all the unique tiles in the hand, and then start checking if there's a sequence of 3 tiles that contain that one in the hand. Detecting if the bot can go Mahjong is even more complicated since it's a combination of detecting if there's 4 sets and a pair in his hand. And that's just a standard Mahjong hand. There's also numerous "special" hands that break those rules but are still a Mahjong hand. For example, "13 unique wonders" consists of 13 specific tiles, "Jade Empire" consists of only tiles colored green, etc. In a perfect world, I'd love to be able to just state the 'rules' of Mahjong, and have the language be able to match a set of 13 tiles against those rules to retrieve which rules it fulfills, for example, checking if it's a Mahjong hand or if it includes a 4 of a kind. Is this something F#'s pattern matching feature can help solve?

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• How to make UISlider output nice rounded numbers exponentially?

  - by RickiG

  Hi I am implementing a UISlider a user can manipulate to set a distance. I have never used the CocoaTouch UISlider, but have used other frameworks sliders, usually there is a variable for setting the "step" and other "helper" properties. The documentation for the UISlider deals only with a max and min value, and the output is always a 6 decimal float with a linear relation to the position of the "slider nob". I guess I will have to implement the desired functionality step by step. To the user, the min/max values range from 10 m to 999 Km, I am trying to implement this in an exponential way, that will feel natural to the user. I.e. the user experiences a feeling of control over the values, big or small. Also that the "output" has reasonable values. Values like 10m 200m 2.5km 150 km etc. instead of 1.2342356 m or 108.93837756 km. I would like for the step size to increase by 10m for the first 200m, then maybe by 50m up to 500m, then when passing the 1000 m value, it starts to deal with Kilometers, so then it is step size = 1 km up until 50 km, then maybe 25 km steps etc. Any way I go about this I end up doing a lot of rounding and a lot of calculations wrapped in a forrest of if statements and NSString/Number conversions, each time the user moves the slider just a little. I was hoping someone could lend me a bit of inspiration/math help or make me aware of a more lean approach to solving this problem. My last idea is to populate and array with a 100 string values, then have the slider int value correspond to a string, this is not very flexible, but doable. Thank you in advance for any help given:)

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• jQuery error when aborting an ajax call only in Internet Explorer

  - by Rob Crowell

  When mousing over an image in a jcarousel, my site displays a popup whose contents are loaded via ajax. I'm doing what I thought was fairly straightforward; keeping a handle to the xhrRequest object, and aborting the existing one before making a new request. It works great in all browsers except IE, where I receive an error "Object doesn't support this property or method" Here's the code that is triggering it: function showPopup { // ... code snipped ... // cancel the existing xhr request if (showPopup.xhrRequest != null) { showPopup.xhrRequest.abort(); showPopup.xhrRequest = null; } showPopup.xhrRequest = $.ajax({url: url, type: "GET", success:function(data) { $("#popup-content").html(data); } }); // ... code snipped ... } showPopup.xhrRequest = null; Works great in Firefox and Chrome. I traced the error down to this bit of code in jquery.js inside the ajax function (line 5233 in my copy of jQuery): // Override the abort handler, if we can (IE doesn't allow it, but that's OK) // Opera doesn't fire onreadystatechange at all on abort try { var oldAbort = xhr.abort; xhr.abort = function() { if (xhr ) { oldAbort.call( xhr ); } onreadystatechange( "abort" ); } catch(e) { } The specific error occurs on the oldAbort.call( xhr ) line. Any ideas?

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• MSIE8 compatibility mode not rendering dynamically created table

  - by KristoferA - Huagati.com

  A bit weird... ...if running in IE8 quirks mode, the table added by the following code doesn't render. Can anyone tell me why, because it is not obvious to me..? <html xmlns="http://www.w3.org/1999/xhtml"> <head> <script> function AddTable() { var table = document.createElement('table'); var row = document.createElement('tr'); table.appendChild(row); var cell = document.createElement('td'); cell.innerHTML='abc'; row.appendChild(cell); var divContainer = document.getElementById('divContainer'); divContainer.appendChild(table); } </script> </head> <body> <div id='divContainer'> </div> <input type='button' value='add table' onclick='javascript:AddTable()' /> </body> </html>

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• Cross-Platform Language + GUI Toolkit for Prototyping Multimedia Applications

  - by msutherl

  I'm looking for a language + GUI toolkit for rapidly prototyping utility applications for multimedia installations. I've been working with Max/MSP/Jitter for many years, but I'd like to add a text-based language to my 'arsenal' for tasks apart from 'content production'. (When it comes to actual media synthesis, my choices are clear [SuperCollider + MSP for audio, Jitter + Quartz + openFrameworks for video]). I'm looking for something that maintains some of the advantages of Max, but is lower-level, faster, more cross-platfrom (Linux support), and text-based. Integration with powerful sound/video libraries is not a requirement. Some requirements: Cross-platform (at least OSX and Linux, Windows is a plus) Fast and easy cross-platform GUIs with no platform-specific modification GUI code separated from backend code as much as possible Good for interfacing with external serial devices (micro-controllers) Good network support (UDP/TCP) Good libraries for multi-media (video, sound, OSC) are a plus Asynchronous synchronous UNIX integration is a plus The options that come to mind: AS3/Flex (not a fan of AS3 or the idea of running in the Flash Player) openFrameworks (C++ framework, perhaps a bit too low level [looking for fast development time] and biased toward video work) Java w/ Processing libraries (like openFrameworks, just slower) Python + Qt (is Qt appropriate for rapid prototyping?) Python + Another GUI toolkit SuperCollider + Swing (yucky GUI development) Java w/ SWT Any other options? What do you recommend?

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• Is there a fast alternative to creating a Texture2D from a Bitmap object in XNA?

  - by Matthew Bowen

  I've looked around a lot and the only methods I've found for creating a Texture2D from a Bitmap are: using (MemoryStream s = new MemoryStream()) { bmp.Save(s, System.Drawing.Imaging.ImageFormat.Png); s.Seek(0, SeekOrigin.Begin); Texture2D tx = Texture2D.FromFile(device, s); } and Texture2D tx = new Texture2D(device, bmp.Width, bmp.Height, 0, TextureUsage.None, SurfaceFormat.Color); tx.SetData<byte>(rgbValues, 0, rgbValues.Length, SetDataOptions.NoOverwrite); Where rgbValues is a byte array containing the bitmap's pixel data in 32-bit ARGB format. My question is, are there any faster approaches that I can try? I am writing a map editor which has to read in custom-format images (map tiles) and convert them into Texture2D textures to display. The previous version of the editor, which was a C++ implementation, converted the images first into bitmaps and then into textures to be drawn using DirectX. I have attempted the same approach here, however both of the above approaches are significantly too slow. To load into memory all of the textures required for a map takes for the first approach ~250 seconds and for the second approach ~110 seconds on a reasonable spec computer. If there is a method to edit the data of a texture directly (such as with the Bitmap class's LockBits method) then I would be able to convert the custom-format images straight into a Texture2D and hopefully save processing time. Any help would be very much appreciated. Thanks

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• Optimizing MySQL for ALTER TABLE of InnoDB

  - by schuilr

  Sometime soon we will need to make schema changes to our production database. We need to minimize downtime for this effort, however, the ALTER TABLE statements are going to run for quite a while. Our largest tables have 150 million records, largest table file is 50G. All tables are InnoDB, and it was set up as one big data file (instead of a file-per-table). We're running MySQL 5.0.46 on an 8 core machine, 16G memory and a RAID10 config. I have some experience with MySQL tuning, but this usually focusses on reads or writes from multiple clients. There is lots of info to be found on the Internet on this subject, however, there seems to be very little information available on best practices for (temporarily) tuning your MySQL server to speed up ALTER TABLE on InnoDB tables, or for INSERT INTO .. SELECT FROM (we will probably use this instead of ALTER TABLE to have some more opportunities to speed things up a bit). The schema changes we are planning to do is adding a integer column to all tables and make it the primary key, instead of the current primary key. We need to keep the 'old' column as well so overwriting the existing values is not an option. What would be the ideal settings to get this task done as quick as possible?

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• How to use my trackpad for horizontal mousewheel scrolling in a Java AWT ScrollPane

  - by blissapp

  Like many modern mice and trackpads, my laptop supports vertical and horizontal scrolling. It's an addictive feature once you get used to it. I simply want my Java apps to support horizontal scrolling via the trackpad/mousewheel, but everywhere I search it seems that this is not possible in Java. I really want someone to tell me that I'm somehow doing it wrong, this feature is already requested behaviour: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6440198 The inability to do this simple thing is actually a deal breaker for the app I'm working on. In fact, for any app I can envision! I've invested a bit of time in the Java backend, so I'd really like to find a solution for this seemingly simple thing. Question is what could I do to implement this behaviour? Are raw OS level events even exposed to java, would I then need to write this from scratch? import java.awt.*; public class ScrollExample extends Canvas { public void paint(Graphics g) { g.setColor(Color.green); g.fillOval(0,0,400, 400); } public static void main(String[] args) { ScrollExample b = new ScrollExample(); Frame f = new Frame ("Scroll Example"); ScrollPane scroller = new ScrollPane (ScrollPane.SCROLLBARS_ALWAYS); scroller.add(b,"Center"); f.setPreferredSize(new Dimension(500,500)); f.add ("Center",scroller); f.pack(); f.show(); } }

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• ASP.NET output caching - dynamically update dependencies

  - by ColinE

  Hi All, I have an ASP.NET application which requires output caching. I need to invalidate the cached items when the data returned from a web service changes, so a simple duration is not good enough. I have been doing a bit of reading about cache dependencies and think I have the right idea. It looks like I will need to create a cache dependency to my web service. To associate the page output with this dependency I think I should use the following method: Response.AddCacheItemDependency(cacheKey); The thing I am struggling with is what I should add to the cache? The dependency my page has is to a single value returned by the web service. My current thinking is that I should create a Custom Cache Dependency via subclassing CacheDependency, and store the current value in the cache. I can then use Response.AddCacheItemDependency to form the dependency. I can then periodically check the value and for a NotifyDependencyChange in order to invalidate my cached HTTP response. The problem is, I need to ensure that the cache is flushed immediately, so a periodic check is not good enough. How can I ensure that my dependant object in the cache which represents the value returned by the web service is re-evaluated before the HTTP response is fetched from the cache? Regards, Colin E.

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• Editing a .class file directly, playing around with opcodes

  - by echox

  Hi, today I just tried to play a little bit around with the opcodes in compiled java class file. After inserting iinc 1,1 the java virtual machine responds with: Exception in thread "main" java.lang.ClassFormatError: Truncated class file at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632) at java.lang.ClassLoader.defineClass(ClassLoader.java:616) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141) at java.net.URLClassLoader.defineClass(URLClassLoader.java:283) at java.net.URLClassLoader.access$000(URLClassLoader.java:58) at java.net.URLClassLoader$1.run(URLClassLoader.java:197) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:248) Could not find the main class: Test. Program will exit. This is my example source code: public class Test { public static void main(String[] args) { int i = 5; i++; i++; i++; System.out.println("Number: " + i + "\n"); } } The opcode for an increment is 0x84 + 2 bytes for operands. There's only one section in the resulting class file, which contains 0x84: [..] 8401 0184 0101 8401 01[..] So I would translate this as: iinc 1,1 iinc 1,1 iinc 1,1 corresponding to my i++; i++; i++; I then tried to append just 840101 to increment the variable once more, but that didn't work and resulted in the ClassFormatError. Is there anything like a checksum for the class file? I looked up the format of a classfile in http://java.sun.com/docs/books/jvms/second_edition/html/ClassFile.doc.html but could not find anything which points out to some kind of bytes_of_classfile or something. I also don't understand why the error is "Truncated Class File", because I did append something :-) I know its not a good idea to edit class files directly, but I'm just interested on the VM internals here.

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• How to develop modular web UIs with Django?

  - by nh2

  When doing larger sites in "big business", you most probalbly work in a team with several developers. Let's say dev A makes a form to insert new user data, B creates a user list, C makes some privilege administration and D does crazy statistic graphs work with image generation and so on. Each dev begins to develop his own component, creates a view and a template and tests that independently, until each component works. Now, the client wants to have all those components on one bit HTML page. How to achieve this? How to assemble different views/templates in a form of composition so that they remain modular and can be developed and tested independently? It seems inheritance is not the way to go because all of those UI components are equal and there is no hierarchy. The idea of the assembling template is something like <html> <head> // include the css for the components and their assembly </head> <body> // include user data form here <some containers, images, and so on> // show user list // show privilege administration in this part // and finally, the nice statistic graphs // perhaps, we want to display some other components here in future </body> </html> I have not found an answer on the net yet. Most people come up with one big template which just implements all of the UI functionality, removing all modularity. Each component shall have its own template and view dealing only with that component developed by one person each, and they then shall be sticked together just like bricks. I would highly appreciate any hints!

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• How to convert from hex-encoded string to a "human readable" string?

  - by John Jensen

  I'm using the Net-SNMP bindings for python and I'm attempting to grab an ARP cache from a Brocade switch. Here's what my code looks like: #!/usr/bin/env python import netsnmp def get_arp(): oid = netsnmp.VarList(netsnmp.Varbind('ipNetToMediaPhysAddress')) res = netsnmp.snmpwalk(oid, Version=2, DestHost='10.0.1.243', Community='public') return res arp_table = get_arp() print arp_table The SNMP code itself is working fine. Output from snmpwalk looks like this: <snip> IP-MIB::ipNetToMediaPhysAddress.128.10.200.6.158 = STRING: 0:1b:ed:a3:ec:c1 IP-MIB::ipNetToMediaPhysAddress.129.10.200.6.162 = STRING: 0:1b:ed:a4:ac:c1 IP-MIB::ipNetToMediaPhysAddress.130.10.200.6.166 = STRING: 0:1b:ed:38:24:1 IP-MIB::ipNetToMediaPhysAddress.131.10.200.6.170 = STRING: 74:8e:f8:62:84:1 </snip> But my output from the python script yields a tuple of hex-encoded strings that looks like this: ('\x00$8C\x98\xc1', '\x00\x1b\xed;_A', '\x00\x1b\xed\xb4\x8f\x81', '\x00$86\x15\x81', '\x00$8C\x98\x81', '\x00\x1b\xed\x9f\xadA', ...etc) I've spent some time googling and came across the struct module and the .decode("hex") string method, but the .decode("hex") method doesn't seem to work: Python 2.7.3 (default, Apr 10 2013, 06:20:15) [GCC 4.6.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> hexstring = '\x00$8C\x98\xc1' >>> newstring = hexstring.decode("hex") Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python2.7/encodings/hex_codec.py", line 42, in hex_decode output = binascii.a2b_hex(input) TypeError: Non-hexadecimal digit found >>> And the documentation for struct is a bit over my head.

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• are there java based auto-updating tools other than WebStart & Eclipse P2?

  - by DaddyB

  Hi, I am working on a java based application and we are looking to ease our deployment of updates. Up until now, we've always simply sent out new install packs & had the sysadmin's on our customer sites roll out the upgrades - painful for a large number of users. what I'd like to do is something similar to java webstart (or eclipse p2) - when the application starts, it checks for updates in a specified location and then downloads the updates prior to starting. But here's my problem - I want more control over what's done outside of the scope of plugins & jar files. For example: I'd like to be able to upate my JVM (we ship a modified version with additional security features). I need to install DLL's - possibly local to the jar files, sometimes to windows Occasiontally run MSI's to install windows components (e.g. printer drivers). I need to modify config files & the registry. I have found a few applications that support this (such as AppLifeUpdate at http://www.kineticjump.com/) but they tend to be .NET focused and it seems a bit perverse to introduce a .NET dependancy on a java application ;) I know I could write my own here, but if there is already a 3rd party library out there that supports this kind of facility, then it would make my life a lot easier. So, has anyone else had a similar problem & knows of some products I could look at? Thanks, Brian.

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• Passing an ActionScript JPG Byte Array to Javscript (and eventually to PHP)

  - by Gus

  Our web application has a feature which uses Flash (AS3) to take photos using the user's web cam, then passes the resulting byte array to PHP where it is reconstructed and saved on the server. However, we need to be able to take this web application offline, and we have chosen Gears to do so. The user takes the app offline, performs his tasks, then when he's reconnected to the server, we "sync" the data back with our central database. We don't have PHP to interact with Flash anymore, but we still need to allow users to take and save photos. We don't know how to save a JPG that Flash creates in a local database. Our hope was that we could save the byte array, a serialized string, or somehow actually persist the object itself, then pass it back to either PHP or Flash (and then PHP) to recreate the JPG. We have tried: - passing the byte array to Javascript instead of PHP, but javascript doesn't seem to be able to do anything with it (the object seems to be stripped of its methods) - stringifying the byte array in Flash, and then passing it to Javascript, but we always get the same string: ÿØÿà Now we are thinking of serializing the string in Flash, passing it to Javascript, then on the return route, passing that string back to Flash which will then pass it to PHP to be reconstructed as a JPG. (whew). Since no one on our team has extensive Flash background, we're a bit lost. Is serialization the way to go? Is there a more realistic way to do this? Does anyone have any experience with this sort of thing? Perhaps we can build a javascript class that is the same as the byte array class in AS?

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• Best way to randomly select rows *per* column in SQL Server

  - by LesterDove

  A search of SO yields many results describing how to select random rows of data from a database table. My requirement is a bit different, though, in that I'd like to select individual columns from across random rows in the most efficient/random/interesting way possible. To better illustrate: I have a large Customers table, and from that I'd like to generate a bunch of fictitious demo Customer records that aren't real people. I'm thinking of just querying randomly from the Customers table, and then randomly pairing FirstNames with LastNames, Address, City, State, etc. So if this is my real Customer data (simplified): FirstName LastName State ========================== Sally Simpson SD Will Warren WI Mike Malone MN Kelly Kline KS Then I'd generate several records that look like this: FirstName LastName State ========================== Sally Warren MN Kelly Malone SD Etc. My initial approach works, but it lacks the elegance that I'm hoping the final answer will provide. (I'm particularly unhappy with the repetitiveness of the subqueries, and the fact that this solution requires a known/fixed number of fields and therefore isn't reusable.) SELECT FirstName = (SELECT TOP 1 FirstName FROM Customer ORDER BY newid()), LastName= (SELECT TOP 1 LastNameFROM Customer ORDER BY newid()), State = (SELECT TOP 1 State FROM Customer ORDER BY newid()) Thanks!

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• Method return type

  - by sarah xia

  Hi, In my company, a system is designed to have 3 layers. Layer1 is responsible for business logic handling. Layer3 is calling back end systems. Layer2 sits between the two layers so that layer1 doesn't need to know about the back end systems. To replay information from layer3, layer2 needs to define interface to layer1. For example, layer1 wants to check if a PIN from user is correct. It calls layer2 checkPin() method and then layer2 calls the relevant back end system. The checkPin() results could be: correctPin, inCorrectPin and internalError. At the moment, we defined the return type 'int'. So if layer2 returns 0, it means correctPin; if 1 is returned, it means inCorrectPin; if 9 is returned it means internalError. It works. However I feel a bit uneasy about this approach. Are there better ways to do it? For example define an enum CheckPinResult{CORRECT_PIN,INCORRECT_PIN,INTERNAL_ERROR}, and return CheckPinResult type? Thanks, Sarah

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• Can't install do_mysql gem?

  - by maccy1

  I'm trying to install the do_mysql on my Snow Leopord system Macbook Pro 13", but I keep getting this error: n216-160:~ myself$ sudo gem1.9 install do_mysql Password: Building native extensions. This could take a while... ERROR: Error installing do_mysql: ERROR: Failed to build gem native extension. /opt/local/bin/ruby1.9 extconf.rb checking for mysql_query() in -lmysqlclient... no *** extconf.rb failed *** Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. Check the mkmf.log file for more details. You may need configuration options. Provided configuration options: --with-opt-dir --without-opt-dir --with-opt-include --without-opt-include=${opt-dir}/include --with-opt-lib --without-opt-lib=${opt-dir}/lib --with-make-prog --without-make-prog --srcdir=. --curdir --ruby=/opt/local/bin/ruby1.9 --with-mysql-config --without-mysql-config --with-mysql-dir --without-mysql-dir --with-mysql-include --without-mysql-include=${mysql-dir}/include --with-mysql-lib --without-mysql-lib=${mysql-dir}/lib --with-mysqlclientlib --without-mysqlclientlib Gem files will remain installed in /opt/local/lib/ruby1.9/gems/1.9.1/gems/do_mysql-0.10.0 for inspection. Results logged to /opt/local/lib/ruby1.9/gems/1.9.1/gems/do_mysql-0.10.0/ext/do_mysql_ext/gem_make.out n216-160:~ myself$ I have no idea why. I also reinstalled my verison of MySQL with the MySQL 5.4.3 beta, 64-bit as others suggested but no dice. Does anyone have any idea what is wrong?

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• Data Modeling of Entity with Attributes

  - by StackOverflowNewbie

  I'm storing some very basic information "data sources" coming into my application. These data sources can be in the form of a document (e.g. PDF, etc.), audio (e.g. MP3, etc.) or video (e.g. AVI, etc.). Say, for example, I am only interested in the filename of the data source. Thus, I have the following table: DataSource Id (PK) Filename For each data source, I also need to store some of its attributes. Example for a PDF would be "numbe of pages." Example for audio would be "bit rate." Example for video would be "duration." Each DataSource will have different requirements for the attributes that need to be stored. So, I have modeled "data source attribute" this way: DataSourceAttribute Id (PK) DataSourceId (FK) Name Value Thus, I would have records like these: DataSource->Id = 1 DataSource->Filename = 'mydoc.pdf' DataSource->Id = 2 DataSource->Filename = 'mysong.mp3' DataSource->Id = 3 DataSource->Filename = 'myvideo.avi' DataSourceAttribute->Id = 1 DataSourceAttribute->DataSourceId = 1 DataSourceAttribute->Name = 'TotalPages' DataSourceAttribute->Value = '10' DataSourceAttribute->Id = 2 DataSourceAttribute->DataSourceId = 2 DataSourceAttribute->Name = 'BitRate' DataSourceAttribute->Value '16' DataSourceAttribute->Id = 3 DataSourceAttribute->DataSourceId = 3 DataSourceAttribute->Name = 'Duration' DataSourceAttribute->Value = '1:32' My problem is that this doesn't seem to scale. For example, say I need to query for all the PDF documents along with thier total number of pages: Filename, TotalPages 'mydoc.pdf', '10' 'myotherdoc.pdf', '23' ... The JOINs needed to produce the above result is just too costly. How should I address this problem?

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• Fast Lightweight Image Comparisson Metric Algorithm

  - by gav

  Hi All, I am developing an application for the Android platform which contains 1000+ image filters that have been 'evolved'. When a user selects a photo I want to present the most relevant filters first. This 'relevance' should be dependent on previous use cases. I have already developed tools that register when a filtered image is saved; this combination of filter and image can be seen as the training data for my system. The issue is that the comparison must occur between selecting an image and the next screen coming up. From a UI point of view I need the whole process to take less that 4 seconds; select an image- obtain a metric to use for similarity - check against use cases - return 6 closest matches. I figure with 4 seconds I can use animations and progress dialogs to keep the user happy. Due to platform contraints I am fairly limited in the computational expense of the algorithm. I have implemented a technique adapted from various online tutorials for running C code on the G1 and hence this language is available Specific Constraints; Qualcomm® MSM7201A™, 528 MHz Processor 320 x 480 Pixel bitmap in 32 bit ARGB ~ 2 seconds computational time for the native method to get the metric ~ 2 seconds to compare the metric of the current image with training data This is an academic project so all ideas are welcome, anything you can think of or have heard about would be of interest to me. My ideas; I want to keep the complexity down (O(n*m)?) by using pixel data only rather than a neighbourhood function I was looking at using the Colour historgram/Greyscale histogram/Texture/Entropy of the image, combining them to make the measure. There will be an obvious loss of information but I need the resultant metric to be substantially smaller than the memory footprint of the image (~0.512 MB) As I said, any ideas to direct my research would be fantastic. Kind regards, Gavin

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• Optimization in Python - do's, don'ts and rules of thumb.

  - by JV

  Well I was reading this post and then I came across a code which was: jokes=range(1000000) domain=[(0,(len(jokes)*2)-i-1) for i in range(0,len(jokes)*2)] I thought wouldn't it be better to calculate the value of len(jokes) once outside the list comprehension? Well I tried it and timed three codes jv@Pioneer:~$ python -m timeit -s 'jokes=range(1000000);domain=[(0,(len(jokes)*2)-i-1) for i in range(0,len(jokes)*2)]' 10000000 loops, best of 3: 0.0352 usec per loop jv@Pioneer:~$ python -m timeit -s 'jokes=range(1000000);l=len(jokes);domain=[(0,(l*2)-i-1) for i in range(0,l*2)]' 10000000 loops, best of 3: 0.0343 usec per loop jv@Pioneer:~$ python -m timeit -s 'jokes=range(1000000);l=len(jokes)*2;domain=[(0,l-i-1) for i in range(0,l)]' 10000000 loops, best of 3: 0.0333 usec per loop Observing the marginal difference 2.55% between the first and the second made me think - is the first list comprehension domain=[(0,(len(jokes)*2)-i-1) for i in range(0,len(jokes)*2)] optimized internally by python? or is 2.55% a big enough optimization (given that the len(jokes)=1000000)? If this is - What are the other implicit/internal optimizations in Python ? What are the developer's rules of thumb for optimization in Python? Edit1: Since most of the answers are "don't optimize, do it later if its slow" and I got some tips and links from Triptych and Ali A for the do's. I will change the question a bit and request for don'ts. Can we have some experiences from people who faced the 'slowness', what was the problem and how it was corrected? Edit2: For those who haven't here is an interesting read Edit3: Incorrect usage of timeit in question please see dF's answer for correct usage and hence timings for the three codes.

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