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  • creating matrix with probabilities

    - by John Chan
    Hi all, I want to generate a matrix of NxN to test some code that I have where each row contains floats as the elements and has to add up to 1 (i.e. a row with a set of probabilities). Where it gets tricky is that I want to make sure that randomly some of the elements should be 0 (in fact most of the elements should be 0 except for some random ones to be the probabilities). I need the probabilities to be 1/m where m is the number of elements that are not 0 within a single row. I tried to think of ways to output this, but essentially I would need this stored in a C++ array. So even if I output to a file I would still have the issue of not having it in array as I need it. At the end of it all I need that array because I want to generate a Market Matrix file. I found an implementation in C++ to take an array and convert it to the market matrix file, so this is what I am basing my findings on. My input for the rest of the code takes in this market matrix file so I need that to be the primary form of output. The language does not matter, I just want to generate the file at the end (I found a way mmwrite and mmread in python as well) Please help, I am stuck and not really sure how to implement this.

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  • Is it possible to wrap an asynchronous event and its callback in a function that returns a boolean?

    - by Rob Flaherty
    I'm trying to write a simple test that creates an image element, checks the image attributes, and then returns true/false. The problem is that using the onload event makes the test asynchronous. On it own this isn't a problem (using a callback as I've done in the code below is easy), but what I can't figure out is how to encapsulate this into a single function that returns a boolean. I've tried various combinations of closures, recursion, and self-executing functions but have had no luck. So my question: am I being dense and overlooking something simple, or is this in fact not possible, because, no matter what, I'm still trying to wrap an asynchronous function in synchronous expectations? Here's the code: var supportsImage = function(callback) { var img = new Image(); img.onload = function() { //Check attributes and pass true or false to callback callback(true); }; img.src = 'data:image/gif;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs='; }; supportsImage(function(status){ console.log(status); }); To be clear, what I want is to be able to wrap this in something such that it can be used like: if (supportsImage) { //Do some crazy stuff } Thanks! (Btw, I know there are a ton of SO questions regarding confusion about synchronous vs. asynchronous. Apologies if this can be reduced to something previously answered.)

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  • Assign C++ instance method to a global-function-pointer ?

    - by umanga
    Greetings, My project structure is as follows: \- base (C static library) callbacks.h callbacks.c paint_node.c . . * libBase.a \-app (C++ application) main.cpp In C library 'base' , I have declared global-function-pointer as: in singleheader file callbacks.h #ifndef CALLBACKS_H_ #define CALLBACKS_H_ extern void (*putPixelCallBack)(); extern void (*putImageCallBack)(); #endif /* CALLBACKS_H_ */ in single C file they are initialized as callbacks.c #include "callbacks.h" void (*putPixelCallBack)(); void (*putImageCallBack)(); Other C files access this callback-functions as: paint_node.c #include "callbacks.h" void paint_node(node *node,int index){ //Call callbackfunction . . putPixelCallBack(node->x,node->y,index); } I compile these C files and generate a static library 'libBase.a' Then in C++ application, I want to assign C++ instance method to this global function-pointer: I did something like follows : in Sacm.cpp file #include "Sacm.h" extern void (*putPixelCallBack)(); extern void (*putImageCallBack)(); void Sacm::doDetection() { putPixelCallBack=(void(*)())&paintPixel; //call somefunctions in 'libBase' C library } void Sacm::paintPixel(int x,int y,int index) { qpainter.begin(this); qpainter.drawPoint(x,y); qpainter.end(); } But when compiling it gives the error: sacmtest.cpp: In member function ‘void Sacm::doDetection()’: sacmtest.cpp:113: error: ISO C++ forbids taking the address of an unqualified or parenthesized non-static member function to form a pointer to member function. Say ‘&Sacm::paintPixel’ sacmtest.cpp:113: error: converting from ‘void (Sacm::)(int, int, int)’ to ‘void ()()’ Any tips?

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  • The perfect web UI framework (with Microsoft stack?) - architecture question?

    - by Igorek
    I'm looking for suggestions for the following issue, and I realize there is really not going to be a perfect answer to my question: I have a UI built in WinForms.NET (v4.0 framework) with WCF back-end and EF4 model objects, that I am looking to port to the web. UI is not huge and is not super complex and is structured well. But it is not a super simple system either. I am looking to pick a technology stack for the web-frontend that will target desktop & partially mobile platforms, provide a good development platform to build on, and facilitate code reuse across UI and back-end tiers... I would rather avoid: custom coding of UI-centric scripts, because they are hard to debug, non-compiled, usually a maintenance nightmare, almost always start to contain business logic, and duplicate some of the logic that back-end tiers have (especially validation) custom-coding for Desktop Web and Mobile Web UI's separately (although I realize that mobile web UI will likely contain fewer of data-entry screens and more reporting screens) non-.NET technology stacks I would love to: target the reporting capabilities of the system toward mobile web browsers not have to write a single line of script (javascript, jquery, etc.) utilize a good collection of controls that produces an elegant UI use .NET for everything The way I see it right now, I need to re-write this app in Silverlight, utilize a 3rd party UI framework like Telerik, and re-do the reports UI again for mobile platforms separately. However, I'm rather concerned about the shelf-life of Silverlight and the needed to deploy a different architecture to deal with mobile platform. Is there an ASP.NET/MVC/Ajax architecture/framework/library that would allow me to get at the power of .NET and without painful (imho) client-side scripting, while providing a decent user experience Thank you

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  • .NET Regex - Replace multiple characters at once without overwriting?

    - by Everaldo Aguiar
    I'm implementing a c# program that should automatize a Mono-alphabetic substitution cipher. The functionality i'm working on at the moment is the simplest one: The user will provide a plain text and a cipher alphabet, for example: Plain text(input): THIS IS A TEST Cipher alphabet: A - Y, H - Z, I - K, S - L, E - J, T - Q Cipher Text(output): QZKL KL QJLQ I thought of using regular expressions since I've been programming in perl for a while, but I'm encountering some problems on c#. First I would like to know if someone would have a suggestion for a regular expression that would replace all occurrence of each letter by its corresponding cipher letter (provided by user) at once and without overwriting anything. Example: In this case, user provides plaintext "TEST", and on his cipher alphabet, he wishes to have all his T's replaced with E's, E's replaced with Y and S replaced with J. My first thought was to substitute each occurrence of a letter with an individual character and then replace that character by the cipherletter corresponding to the plaintext letter provided. Using the same example word "TEST", the steps taken by the program to provide an answer would be: 1 - replace T's with (lets say) @ 2 - replace E's with # 3 - replace S's with & 4 - Replace @ with E, # with Y, & with j 5 - Output = EYJE This solution doesn't seem to work for large texts. I would like to know if anyone can think of a single regular expression that would allow me to replace each letter in a given text by its corresponding letter in a 26-letter cipher alphabet without the need of splitting the task in an intermediate step as I mentioned. If it helps visualize the process, this is a print screen of my GUI for the program:

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  • IIS URL Rewrite rule - Default document for subdirectories

    - by Antonio Bakula
    I would like create URL rewrite rule that will set default document for my virtual folders. eg. someting like this www.domain.com/en/ -> www.domain.com/en/index.aspx www.domain.com/hr/ -> www.domain.com/hr/index.aspx www.domain.com/de/ -> www.domain.com/de/index.aspx directories en, hr, de doesn't really exists on web server they are just markers for languange used in site used by home grown http module that will rewrite path with query params. Quick solution was define rule for every single lang, something like this : <rewrite> <rewriteMaps> <rewriteMap name="Langs"> <add key="/en" value="/en/index.aspx" /> <add key="/hr" value="/hr/index.aspx" /> <add key="/de" value="/de/index.aspx" /> </rewriteMap> </rewriteMaps> <rules> But I would really like solution that would not require changes in web.config and adding rewrite rule for every languange used on particular site. Thanks !

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  • "Android Create" call fails in windows 7 - missing JDK

    - by reuscam
    I'm having a problem getting my android dev environment setup in Windows 7. I follow the instructions here, as well as several environment sublinks. I am using Eclipse with the Android plugin. I have installed the Java JDK several times, in various locations (jdk-6u20-windows-i586.exe) - but I am obviously missing something. Every time I run "android create avd --target 2 --name my_avd" I get an error: C:\Users\andrew>android create avd --target 2 --name my_avd WARNING: Java not found in your path. Checking it it's installed in C:\Program Files\Java instead. ERROR: No suitable Java found. In order to properly use the Android Developer Tools, you need a suitable version of Java installed on your system. We recommend that you install the JDK version of JavaSE, available here: http://java.sun.com/javase/downloads/ You can find the complete Android SDK requirements here: http://developer.android.com/sdk/requirements.html This error message is the reason for me installing the JDK several times over. First I tried installing to a location on my e: drive. I then moved it to the default loc (program files (x86)\java\jdk.6.something. I also tried forcing it to go into the program files\ path, but it still automatically installs into the (x86) path. I have added the install path to my path environment variable every single time, yet I still continue to get this error. My suspicion is that windows 7 and the android tools are not playing together well in terms of finding the JDK, but who knows, it may be something entirely different. If you have seen this error before, I would appreciate a hint.

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  • JDBC transaction dead-lock solution required?

    - by user49767
    It's a scenario described my friend and challenged to find solution. He is using Oracle database and JDBC connection with read committed as transaction isolation level. In one of the transaction, he updates a record and executes selects statement and commits the transaction. when everything happening within single thread, things are fine. But when multiple requests are handled, dead-lock happens. Thread-A updates a record. Thread B updates another record. Thread-A issues select statement and waits for Thread-B's transaction to complete the commit operation. Thread-B issues select statement and waits for Thread-A's transaction to complete the commit operation. Now above causes dead-lock. Since they use command pattern, the base framework allows to issue commit only once (at the end of all the db operation), so they are unable to issue commit immediately after select statement. My argument was Thread-A supposed to select all the records which are committed and hence should not be issue. But he said that Thread-A will surely wait till Thread-B commits the record. is that true? What are all the ways, to avoid the above issue? is it possible to change isolation-level? (without changing underlying java framework) Little information about base framework, it is something similar to Struts action, their each and every request handled by one action, transaction begins before execution and commits after execution.

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  • How do I debug into an ILMerged assembly?

    - by Rory Becker
    Summary I want to alter the build process of a 2-assembly solution, such that a call to ILMerge is invoked, and the build results in a single assembly. Further I would like to be able to debug into the resultant assembly. Preparation - A simple example New Solution - ClassLibrary1 Create a static function 'GetMessage' in Class1 which returns the string "Hello world" Create new console app which references the ClassLibrary. Output GetMessage from main() via the console. You now have a 2 assembly app which outputs "Hello World" to the console. So what next..? I would like to alter the Console app build process, to include a post build step which uses ILMerge, to merge the ClassLibrary assembly into the Console assembly After this step I should be able to: Run the Console app directly with no ClassLibrary1.dll present Run the Console app via F5 (or F11) in VS and be able to debug into each of the 2 projects. Limited Success I read this blogpost and managed to achieve the merge I was after with a post-build command of... "$(ProjectDir)ILMerge.bat" "$(TargetDir)" $(ProjectName) ...and an ILMerge.bat file which read... CD %1 Copy %2.exe temp.exe ILMerge.exe /out:%2.exe temp.exe ClassLibrary1.dll Del temp.exe Del ClassLibrary1.* This works fairly well, and does in fact produce an exe which runs outside the VS environment as required. However it does not appear to produce symbols (.pdb file) which VS is able to use in order to debug into the code. I think this is the last piece of the puzzle. Does anyone know how I can make this work? FWIW I am running VS2010 on an x64 Win7 x64 machine.

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  • How to optimize Conway's game of life for CUDA?

    - by nlight
    I've written this CUDA kernel for Conway's game of life: global void gameOfLife(float* returnBuffer, int width, int height) { unsigned int x = blockIdx.x*blockDim.x + threadIdx.x; unsigned int y = blockIdx.y*blockDim.y + threadIdx.y; float p = tex2D(inputTex, x, y); float neighbors = 0; neighbors += tex2D(inputTex, x+1, y); neighbors += tex2D(inputTex, x-1, y); neighbors += tex2D(inputTex, x, y+1); neighbors += tex2D(inputTex, x, y-1); neighbors += tex2D(inputTex, x+1, y+1); neighbors += tex2D(inputTex, x-1, y-1); neighbors += tex2D(inputTex, x-1, y+1); neighbors += tex2D(inputTex, x+1, y-1); __syncthreads(); float final = 0; if(neighbors < 2) final = 0; else if(neighbors 3) final = 0; else if(p != 0) final = 1; else if(neighbors == 3) final = 1; __syncthreads(); returnBuffer[x + y*width] = final; } I am looking for errors/optimizations. Parallel programming is quite new to me and I am not sure if I get how to do it right. The rest of the app is: Memcpy input array to a 2d texture inputTex stored in a CUDA array. Output is memcpy-ed from global memory to host and then dealt with. As you can see a thread deals with a single pixel. I am unsure if that is the fastest way as some sources suggest doing a row or more per thread. If I understand correctly NVidia themselves say that the more threads, the better. I would love advice on this on someone with practical experience.

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  • Lights off effect and jquery placement on wordpress

    - by Alexander Santiago
    I'm trying to implement a lights on/off on single posts of my wordpress theme. I know that I have to put this code on my css, which I did already: #the_lights{ background-color:#000; height:1px; width:1px; position:absolute; top:0; left:0; display:none; } #standout{ padding:5px; background-color:white; position:relative; z-index:1000; } Now this is the code that I'm having trouble with: function getHeight() { if ($.browser.msie) { var $temp = $("").css("position", "absolute") .css("left", "-10000px") .append($("body").html()); $("body").append($temp); var h = $temp.height(); $temp.remove(); return h; } return $("body").height(); } $(document).ready(function () { $("#the_lights").fadeTo(1, 0); $("#turnoff").click(function () { $("#the_lights").css("width", "100%"); $("#the_lights").css("height", getHeight() + "px"); $("#the_lights").css({‘display’: ‘block’ }); $("#the_lights").fadeTo("slow", 1); }); $("#soft").click(function () { $("#the_lights").css("width", "100%"); $("#the_lights").css("height", getHeight() + "px"); $("#the_lights").css("display", "block"); $("#the_lights").fadeTo("slow", 0.8); }); $("#turnon").click(function () { $("#the_lights").css("width", "1px"); $("#the_lights").css("height", "1px"); $("#the_lights").css("display", "block"); $("#the_lights").fadeTo("slow", 0); }); }); I think it's a jquery. Where do I place it and how do I call it's function? Been stuck on this thing for 6 hours now and any help would be greatly appreciated...

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  • Should methods that are required to be executed in a specific order be private?

    - by TooFat
    I have a Class that retrieves some data and images does some stuff to them and them uploads them to a third party app using web services. The object needs to perform some specific steps in order. My question is should I be explicitly exposing each method publicly like so. myObject obj = new myObject(); obj.RetrieveImages(); obj.RetrieveAssociatedData(); obj.LogIntoThirdPartyWebService(); obj.UploadStuffToWebService(); or should all of these methods be private and encapsulated in a single public method like so. public class myObject() { private void RetrieveImages(){}; private void RetrieveAssociatedData(){}; private void LogIntoThirdPartyWebService(){}; private void UploadStuffToWebService(){}; public void DoStuff() { this.RetrieveImages(); this.RetrieveAssociatedData(); this.LogIntoThirdPartyWebService(); this.UploadStuffToWebService(); } } which is called like so. myObject obj = new myObject(); obj.DoStuff();

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  • Is there any appreciable difference between if and if-else?

    - by Drew
    Given the following code snippets, is there any appreciable difference? public boolean foo(int input) { if(input > 10) { doStuff(); return true; } if(input == 0) { doOtherStuff(); return true; } return false; } vs. public boolean foo(int input) { if(input > 10) { doStuff(); return true; } else if(input == 0) { doOtherStuff(); return true; } else { return false; } } Or would the single exit principle be better here with this piece of code... public boolean foo(int input) { boolean toBeReturned = false; if(input > 10) { doStuff(); toBeReturned = true; } else if(input == 0) { doOtherStuff(); toBeReturned = true; } return toBeReturned; } Is there any perceptible performance difference? Do you feel one is more or less maintainable/readable than the others?

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  • CakePHP 1.26: Bug in 'Security' component?

    - by Steve
    Okay, for those of you who may have read this earlier, I've done a little research and completely revamped my question. I've been having a problem where my form requests get blackholed by the Security component, although everything works fine when the Security component is disabled. I've traced it down to a single line in a form: <?php echo $form->create('Audition');?> <fieldset> <legend><?php __('Edit Audition');?></legend> <?php echo $form->input('ensemble'); echo $form->input('position'); echo $form->input('aud_date'); // The following line works fine... echo $form->input('owner'); // ...but the following line blackholes when Security included // and the form is submitted: // echo $form->input('owner', array('disabled'=>'disabled'); ?> </fieldset> <?php echo $form->end('Submit');?> (I've commented out the offending line for clarity) I think I'm following the rules by using the form helper; as far as I can tell, this is a bug in the Security component, but I'm too much of a CakePHP n00b to know for sure. I'd love to get some feedback, and if it's a real bug, I'll submit it to the CakePHP team. I'd also love to know if I'm just being dumb and missing something obvious here.

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  • Fetch the most viewed data in databases

    - by Erik Edgren
    I want to get the most viewed photo from the database but I don't know how I shall accomplish this. Here's my SQL at the moment: SELECT * FROM photos AS p, viewers AS v WHERE p.id = v.id_photo GROUP BY v.id_photo The databases: CREATE TABLE IF NOT EXISTS `photos` ( `id` int(10) NOT NULL AUTO_INCREMENT, `photo_filename` varchar(50) NOT NULL, `photo_camera` varchar(150) NOT NULL, `photo_taken` datetime NOT NULL, `photo_resolution` varchar(10) NOT NULL, `photo_exposure` varchar(10) NOT NULL, `photo_iso` varchar(3) NOT NULL, `photo_fnumber` varchar(10) NOT NULL, `photo_focallength` varchar(10) NOT NULL, `post_coordinates` text NOT NULL, `post_description` text NOT NULL, `post_uploaded` datetime NOT NULL, `post_edited` datetime NOT NULL, `checkbox_approxcoor` enum('0','1') NOT NULL DEFAULT '0', PRIMARY KEY (`id`), UNIQUE KEY `id` (`id`) ) CREATE TABLE IF NOT EXISTS `viewers` ( `id` int(10) NOT NULL AUTO_INCREMENT, `id_photo` int(10) DEFAULT '0', `ipaddress` text NOT NULL, `date_viewed` datetime NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `id` (`id`) ) The data in viewers looks like this: (1, 85, '3892a0ab97d6ff325f285b27b847070f', '2012-06-21 22:49:25'), (2, 84, '3892a0ab97d6ff325f285b27b847070f', '2012-06-21 22:49:25'), (3, 85, '3892a0ab97d6ff325f285b27b847070f', '2012-06-21 22:49:25'); One single row from the database for photos to understand how the rows looks like in this database: (85, 'P1170986.JPG', 'Panasonic DMC-LX3', '2012-06-19 18:00:40', '3968x2232', '10/8000', '80', '50/10', '51/10', '', '', '2012-06-19 18:45:17', '0000-00-00 00:00:00', '0') At the moment the SQL only prints the photo with ID 84. In this case it's wrong - it should print out the photo with ID 85. How can I fix this problem? Thanks in advance.

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  • Java: extending Object class

    - by Fabio F.
    Hello, I'm writing (well, completing) an "extension" of Java which will help role programming. I translate my code to Java code with javacc. My compilers add to every declared class some code. Here's an example to be clearer: MyClass extends String implements ObjectWithRoles { //implements... is added /*Added by me */ public setRole(...){...} public ... /*Ends of stuff added*/ ...//myClass stuff } It adds Implements.. and the necessary methods to EVERY SINGLE CLASS you declare. Quite rough, isnt'it? It will be better if I write my methods in one class and all class extends that.. but.. if class already extends another class (just like the example)? I don't want to create a sort of wrapper that manage roles because i don't want that the programmer has to know much more than Java, few new reserved words and their use. My idea was to extends java.lang.Object.. but you can't. (right?) Other ideas? I'm new here, but I follow this site so thank you for reading and all the answers you give! (I apologize for english, I'm italian)

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  • How can this code throw a NullReferenceException?

    - by Davy8
    I must be going out of my mind, because my unit tests are failing because the following code is throwing a null ref exception: int pid = 0; if (parentCategory != null) { Console.WriteLine(parentCategory.Id); pid = parentCategory.Id; } The line that's throwing it is: pid = parentCategory.Id; The console.writeline is just to debug in the NUnit GUI, but that outputs a valid int. Edit: It's single-threaded so it can't be assigned to null from some other thread, and the fact the the Console.WriteLine successfully prints out the value shows that it shouldn't throw. Edit: Relevant snippets of the Category class: public class Category { private readonly int id; public Category(Category parent, int id) { Parent = parent; parent.PerformIfNotNull(() => parent.subcategories.AddIfNew(this)); Name = string.Empty; this.id = id; } public int Id { get { return id; } } } Well if anyone wants to look at the full code, it's on Google Code at http://code.google.com/p/chefbook/source/checkout I think I'm going to try rebooting the computer... I've seen pretty weird things fixed by a reboot. Will update after reboot. Update: Mystery solved. Looks like NUnit shows the error line as the last successfully executed statement... Copy/pasted test into new console app and ran in VS showed that it was the line after the if statement block (not shown) that contained a null ref. Thanks for all the ideas everyone. +1 to everyone that answered.

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  • Is there really such a thing as a char or short in modern programming?

    - by Dean P
    Howdy all, I've been learning to program for a Mac over the past few months (I have experience in other languages). Obviously that has meant learning the Objective C language and thus the plainer C it is predicated on. So I have stumbles on this quote, which refers to the C/C++ language in general, not just the Mac platform. With C and C++ prefer use of int over char and short. The main reason behind this is that C and C++ perform arithmetic operations and parameter passing at integer level, If you have an integer value that can fit in a byte, you should still consider using an int to hold the number. If you use a char, the compiler will first convert the values into integer, perform the operations and then convert back the result to char. So my question, is this the case in the Mac Desktop and IPhone OS environments? I understand when talking about theses environments we're actually talking about 3-4 different architectures (PPC, i386, Arm and the A4 Arm variant) so there may not be a single answer. Nevertheless does the general principle hold that in modern 32 bit / 64 bit systems using 1-2 byte variables that don't align with the machine's natural 4 byte words doesn't provide much of the efficiency we may expect. For instance, a plain old C-Array of 100,000 chars is smaller than the same 100,000 ints by a factor of four, but if during an enumeration, reading out each index involves a cast/boxing/unboxing of sorts, will we see overall lower 'performance' despite the saved memory overhead?

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  • MySQL Ratings From Two Tables

    - by DirtyBirdNJ
    I am using MySQL and PHP to build a data layer for a flash game. Retrieving lists of levels is pretty easy, but I've hit a roadblock in trying to fetch the level's average rating along with it's pointer information. Here is an example data set: levels Table: level_id | level_name 1 | Some Level 2 | Second Level 3 | Third Level ratings Table: rating_id | level_id | rating_value 1 | 1 | 3 2 | 1 | 4 3 | 1 | 1 4 | 2 | 3 5 | 2 | 4 6 | 2 | 1 7 | 3 | 3 8 | 3 | 4 9 | 3 | 1 I know this requires a join, but I cannot figure out how to get the average rating value based on the level_id when I request a list of levels. This is what I'm trying to do: SELECT levels.level_id, AVG(ratings.level_rating WHERE levels.level_id = ratings.level_id) FROM levels I know my SQL is flawed there, but I can't figure out how to get this concept across. The only thing I can get to work is returning a single average from the entire ratings table, which is not very useful. Ideal Output from the above conceptually valid but syntactically awry query would be: level_id | level_rating 1| 3.34 2| 1.00 3| 4.54 My main issue is I can't figure out how to use the level_id of each response row before the query has been returned. It's like I want to use a placeholder... or an alias... I really don't know and it's very frustrating. The solution I have in place now is an EPIC band-aid and will only cause me problems long term... please help!

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  • How do I relate two models/tables in Django based on non primary non unique keys?

    - by wizard
    I've got two tables that I need to relate on a single field po_num. The data is imported from another source so while I have a little bit of control over what the tables look like but I can't change them too much. What I want to do is relate these two models so I can look up one from the other based on the po_num fields. What I really need to do is join the two tables so I can do a where on a count of the related table. I would like to do filter for all Order objects that have 0 related EDI856 objects. I tried adding a foreign key to the Order model and specified the db_column and to_fields as po_num but django didn't like that the fact that Edi856.po_num wasn't unique. Here are the important fields of my current models that let me display but not filter for the data that I want. class Edi856(models.Model): po_num = models.CharField(max_length=90, db_index=True ) class Order(models.Model): po_num = models.CharField(max_length=90, db_index=True) def in_edi(self): '''Has the edi been processed?''' return Edi856.objects.filter(po_num = self.po_num).count() Thanks for taking the time to read about my problem. I'm not sure what to do from here.

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  • Why is my django bulk database population so slow and frequently failing?

    - by bryn
    I decided I'd like to use django's model system rather than coding raw SQL to interface with my database, but I am having a problem that surely is avoidable. My models.py contains: class Student(models.Model): student_id = models.IntegerField(unique = True) form = models.CharField(max_length = 10) preferred = models.CharField(max_length = 70) surname = models.CharField(max_length = 70) and I'm populating it by looping through a list as follows: from models import Student for id, frm, pref, sname in large_list_of_data: s = Student(student_id = id, form = frm, preferred = pref, surname = sname) s.save() I don't really want to be saving this to the database each time but I don't know another way to get django to not forget about it (I'd rather add all the rows and then do a single commit). There are two problems with the code as it stands. It's slow -- about 20 students get updated each second. It doesn't even make it through large_list_of_data, instead throwing a DatabaseError saying "unable to open database file". (Possibly because I'm using sqlite3.) My question is: How can I stop these two things from happening? I'm guessing that the root of both problems is that I've got the s.save() but I don't see a way of easily batching the students up and then saving them in one commit to the database.

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  • Design patterns for Agent / Actor based concurrent design.

    - by nso1
    Recently i have been getting into alternative languages that support an actor/agent/shared nothing architecture - ie. scala, clojure etc (clojure also supports shared state). So far most of the documentation that I have read focus around the intro level. What I am looking for is more advanced documentation along the gang of four but instead shared nothing based. Why ? It helps to grok the change in design thinking. Simple examples are easy, but in a real world java application (single threaded) you can have object graphs with 1000's of members with complex relationships. But with agent based concurrency development it introduces a whole new set of ideas to comprehend when designing large systems. ie. Agent granularity - how much state should one agent manage - implications on performance etc or are their good patterns for mapping shared state object graphs to agent based system. tips on mapping domain models to design. Discussions not on the technology but more on how to BEST use the technology in design (real world "complex" examples would be great).

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  • Cocoa framework development: sharing between projects

    - by e.James
    I am currently developing a handful of similar Cocoa desktop apps. In an effort to share code between them, I have identified a set of core classes and functions that can be common across all of these applications. I would like to bundle this common code into a framework which all of my current applications (and any future ones) can link against. Now, here's the hard part: I'm going to be developing this framework as I go, so I need each of my desktop apps to have a reference to it, but I want to be able to edit the framework source code from within each of the app projects and have the framework automatically rebuilt as required. For example, let's say I have the Xcode project for DesktopAppNumberOne open, and I decide that one of my framework classes needs to be changed. I would like to: Open and edit the source file for that framework class without having to open the framework project in Xcode. Hit "build" on DesktopAppNumberOne, and see the framework rebuilt first (because one of its sources has changed), then see parts of DesktopAppNumberOne rebuilt (because one of the frameworks it links against has changed). I can see how to do this with only one app and one framework, but I'm having trouble figuring out how to do it with multiple apps that share a single framework. Has anyone had success with this approach? Am I perhaps going about this the wrong way? Any help would be appreciated.

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  • Executing logic before save or validation with EF Code-First Models

    - by Ryan Norbauer
    I'm still getting accustomed to EF Code First, having spent years working with the Ruby ORM, ActiveRecord. ActiveRecord used to have all sorts of callbacks like before_validation and before_save, where it was possible to modify the object before it would be sent off to the data layer. I am wondering if there is an equivalent technique in EF Code First object modeling. I know how to set object members at the time of instantiation, of course, (to set default values and so forth) but sometimes you need to intervene at different moments in the object lifecycle. To use a slightly contrived example, say I have a join table linking Authors and Plays, represented with a corresponding Authoring object: public class Authoring { public int ID { get; set; } [Required] public int Position { get; set; } [Required] public virtual Play Play { get; set; } [Required] public virtual Author Author { get; set; } } where Position represents a zero-indexed ordering of the Authors associated to a given Play. (You might have a single "South Pacific" Play with two authors: a "Rodgers" author with a Position 0 and a "Hammerstein" author with a Position 1.) Let's say I wanted to create a method that, before saving away an Authoring record, it checked to see if there were any existing authors for the Play to which it was associated. If no, it set the Position to 0. If yes, it would find set the Position of the highest value associated with that Play and increment by one. Where would I implement such logic within an EF code first model layer? And, in other cases, what if I wanted to massage data in code before it is checked for validation errors? Basically, I'm looking for an equivalent to the Rails lifecycle hooks mentioned above, or some way to fake it at least. :)

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  • ArrayList<Int> Collections.Sort and LineNumberReader Help How to

    - by user1819551
    I have a issue i can't get it to work now let going to the point a explain in the code thanks. This is my class: what I want to do is insert the Integers sort the list and buffer writer in a column with out coma. Now I getting this: [1110018, 1110032, 1110056, 1110059, 1110063, 1110085, 1110096, 1110123, 1110125, 1110185, 1110456, 1110459] I want like this: 111xxxxx 111xxxx xxxx....... I can't do it in single array, have to be in ArrayList. This is my collecting: list.addNumbers(numbers); list.display(); This is my writer: Is buffered coma.write("\n"+list.display()); coma.flush();<br/> Here is my class: public class IdCount {<br/> private ArrayList<Integer> properNumber = new ArrayList<>(); public void addNumbers(Integer numbers) { properNumber.add(numbers); Collections.sort(properNumber); } public String display() { //(I try .toString() Not work) return properNumber.toString(); } My second issue is LineNumberReader: This is my collecting and my writing: try { Reader input = new BufferedReader( new FileReader(inputFile)); try (Scanner in = new Scanner(input)) { while (in.hasNext()) { //(More Code) asp = new LineNumberReader(input); int rom = 0; while (asp.readLine()!=null){ rom++; } System.out.println(rom); coma.write(rom); This one will not write anything an my System Print give me only 12 0 in column.

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