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  • How can I use System.Web.Caching.Cache in a Console application?

    - by Ron Klein
    Context: .Net 3.5, C# I'd like to have caching mechanism in my Console application. Instead of re-inventing the wheel, I'd like to use System.Web.Caching.Cache (and that's a final decision, I can't use other caching framework, don't ask why). However, it looks like System.Web.Caching.Cache is supposed to run only in a valid HTTP context. My very simple snippet looks like this: using System; using System.Web.Caching; using System.Web; Cache c = new Cache(); try { c.Insert("a", 123); } catch (Exception ex) { Console.WriteLine("cannot insert to cache, exception:"); Console.WriteLine(ex); } and the result is: cannot insert to cache, exception: System.NullReferenceException: Object reference not set to an instance of an object. at System.Web.Caching.Cache.Insert(String key, Object value) at MyClass.RunSnippet() So obviously, I'm doing something wrong here. Any ideas? Update: +1 to most answers, getting the cache via static methods is the correct usage, namely HttpRuntime.Cache and HttpContext.Current.Cache. Thank you all!

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  • Perceptron Classification and Model Training

    - by jake pinedo
    I'm having an issue with understanding how the Perceptron algorithm works and implementing it. cLabel = 0 #class label: corresponds directly with featureVectors and tweets for m in range(miters): for point in featureVectors: margin = answers[cLabel] * self.dot_product(point, w) if margin <= 0: modifier = float(lrate) * float(answers[cLabel]) modifiedPoint = point for x in modifiedPoint: if x != 0: x *= modifier newWeight = [modifiedPoint[i] + w[i] for i in range(len(w))] w = newWeight self._learnedWeight = w This is what I've implemented so far, where I have a list of class labels in answers and a learning rate (lrate) and a list of feature vectors. I run it for the numbers of iterations in miter and then get the final weight at the end. However, I'm not sure what to do with this weight. I've trained the perceptron and now I have to classify a set of tweets, but I don't know how to do that. EDIT: Specifically, what I do in my classify method is I go through and create a feature vector for the data I'm given, which isn't a problem at all, and then I take the self._learnedWeight that I get from the earlier training code and compute the dot-product of the vector and the weight. My weight and feature vectors include a bias in the 0th term of the list so I'm including that. I then check to see if the dotproduct is less than or equal to 0: if so, then I classify it as -1. Otherwise, it's 1. However, this doesn't seem to be working correctly.

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  • ANTLR Tree Grammar and StringTemplate Code Translation

    - by Behrooz Nobakht
    I am working on a code translation project with a sample ANTLR tree grammar as: start: ^(PROGRAM declaration+) -> program_decl_tmpl(); declaration: class_decl | interface_decl; class_decl: ^(CLASS ^(ID CLASS_IDENTIFIER)) -> class_decl_tmpl(cid={$CLASS_IDENTIFIER.text}); The group template file for it looks like: group My; program_decl_tmpl() ::= << *WHAT?* >> class_decl_tmpl(cid) ::= << public class <cid> {} >> Based on this, I have these questions: Everything works fine apart from that what I should express in WHAT? to say that a program is simply a list of class declarations to get the final generated output? Is this approach averagely suitable for not so a high-level language? I have also studied ANTLR Code Translation with String Templates, but it seems that this approach takes much advantage of interleaving code in tree grammar. Is it also possible to do it as much as possible just in String Templates?

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  • Linear feedback shift register?

    - by Mattia Gobbi
    Lately I bumped repeatedly into the concept of LFSR, that I find quite interesting because of its links with different fields and also fascinating in itself. It took me some effort to understand, the final help was this really good page, much better than the (at first) cryptic wikipedia entry. So I wanted to write some small code for a program that worked like a LFSR. To be more precise, that somehow showed how a LFSR works. Here's the cleanest thing I could come up with after some lenghtier attempts (Python): def lfsr(seed, taps): sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor sr, xor = str(xor) + sr[:-1], 0 print sr if sr == seed: break lfsr('11001001', (8,7,6,1)) #example I named "xor" the output of the XOR function, not very correct. However, this is just meant to show how it circles through its possible states, in fact you noticed the register is represented by a string. Not much logical coherence. This can be easily turned into a nice toy you can watch for hours (at least I could :-) def lfsr(seed, taps): import time sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor print time.sleep(0.75) sr, xor = str(xor) + sr[:-1], 0 print sr print time.sleep(0.75) Then it struck me, what use is this in writing software? I heard it can generate random numbers; is it true? how? So, it would be nice if someone could: explain how to use such a device in software development come up with some code, to support the point above or just like mine to show different ways to do it, in any language Also, as theres not much didactic stuff around about this piece of logic and digital circuitry, it would be nice if this could be a place for noobies (like me) to get a better understanding of this thing, or better, to understand what it is and how it can be useful when writing software. Should have made it a community wiki? That said, if someone feels like golfing... you're welcome.

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  • algorithm || method to write prog

    - by fatai
    I am one of the computer science student. My wonder is everyone solve problem with different or same method, but actually I dont know whether they use method or I dont know whether there are such common method to approach problem. All teacher give us problem which in simple form sometimes, but they dont introduce any approach or method(s) so that we can first choose method then apply that one to problem , afterward find solution then write code. I have found one method when I failed the course, More accurately, When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 But now, I wonder other method ; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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  • Regex help in java validations

    - by user1697113
    Hi i want to do some validations.I used to put regex in JS but im new to regex in java, so i tried to make up a code on similar lines in java. Here is what i did. 1)Check whether first character in string is alphanumeric. 2)Check whether the string atleast 1 number. so i wrote a code, but it is always returning false.I am not sure if i'm doing this correctly. private static boolean checkEmbeddedPassword(final String field) { boolean returnValue=true; String testpatternAlpha="/^[A-Za-z0-9].+$/"; String testNumber="/[0-9]/"; Pattern pattern=Pattern.compile(testpatternAlpha); Pattern pattern2=Pattern.compile(testNumber); Matcher matcher = pattern.matcher(field); Matcher matcher2 = pattern2.matcher(field); boolean firstChar=matcher.matches(); boolean numberFlag=matcher2.matches(); System.out.println("-----the value of pwd iss-----"+field); System.out.println("---------Regex---------Out--put-----"+firstChar); System.out.println("---------Regex---------Out- for numeral-put-----"+numberFlag); if(firstChar){ returnValue=false; } else if(field.contains(" ")) { System.out.println("-----------cannot have space------"); returnValue=false; } else if(numberFlag) { returnValue=false; } return returnValue; }

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  • Flex 3 - Saving an image of a component

    - by Emma
    Im currently trying to work the imageSnapshot function in flex. Ive been looking hard but I cant seem to find a solution to my problem. I wish to take a screenshot of one of my components, to capture the final output of my program, since a plain "printscreen" cuts off some of the output due to it scrolling. My current code looks like - <mx:ApplicationControlBar dock="true"> <mx:Button label="Take snapshot of Profile" click="takeSnapshot();" /> </mx:ApplicationControlBar> Which when called does - private function takeSnapshot(even:Event=null):void { var imageSnap:ImageSnapshot = ImageSnapshot.captureImage(viewstack1); Now i think this is taking the image of the viewstack which I want... But Im stumped on what to do from here! Is it not possible to now just copy the image to the clipboard, or produce a new window in my browser with the entire image inside? If anyone has any other way to do this, suggestions would be wonderful. Thank you for your time.

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  • Is it possible to alternate between two types in an XML Schema

    - by lief79
    I'm wondering if I am missing something obvious. I have a list of numbers, possibly including ranges (think of the print page option of a print dialog). Ideally I'd like to have the final XML output look like this, with page and pageRange in an order. <pages> <page> 1</page> <pageRange><start>3</start><end>6</end></pageRange> <page> 34</page> </pages> What would I have to put into a schema to allow this? From what I saw: Sequence with multiple page and page Range allowed doesn't permit alternation. Choice only allows one or the other. I tried messing with all, but I wasn't getting it to validate properly. My short term solution is to have a sequence of ranges, and to force single numbers into the range, but it seems potentially cumbersome. So am I missing something?

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  • What framework would allow for the largest coverage of freelance developers in the media/digital mar

    - by optician
    This question is not about which is the best, it is about which makes the most business sense to use as a company's platform of choice for ongoing freelance development. I'm currently trying to decide what framework to move my company in regarding frameworks for web application work. Options are ASP.NET MVC Django CakePHP/Symfony etc.. Struts Pearl on Rails Please feel free to add more to the discussion. I currently work in ASP.NET MVC in my Spare time, and find it incredibly enjoyable to work with. It is my first experince with an MVC framework for the web, so I can't talk on the others. The reason for not pushing this at the company is that I feel that there are not many developers in the Media/Marketing world who would work with this, so it may be hard to extend the team, or at least cost more. I would like to move into learning and pushing Django, partly to learn python, partly to feel a bit cooler (all my geeky friends use Java/Python/c++). Microsoft is the dark side to most company's I work with (Marketing/Media focused). But again I'm worried about developers in this sector. PHP seems like the natural choice, but I'm scared by the sheer amount of possible frameworks, and also that the quality of developer may be lower. I know there are great php developers out there, but how many of them know multiple frameworks? Are they similar enough that anyone decent at php can pick them up? Just put struts in the list as an option, but personally I live with a Java developer, and considering my experience with c#, I'm just not that interested in learning Java (selfish personal geeky reasons) Final option was a joke http://www.bbc.co.uk/blogs/radiolabs/2007/11/perl_on_rails.shtml

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  • Why does 12:20 PM parse to 0:20 on the next day?

    - by Hanno Fietz
    I'm using java.text.SimpleDateFormat to parse string representations of date/time values inside an XML document. I'm seeing all times that have an hour value of 12 shifted by 12 hours into the future, i. e. 20 minutes past noon gets parsed to mean 20 minutes past midnight the following day. I wrote a unit test which seems to confirm that the error is made upon parsing (I checked the return values from getTime() with the linux shell command date). Now I'm wondering: is there a bug in the parse() method? is there something wrong with the input string? am I using the wrong format string for the input? The input data is taken from Yahoo's YWeather service. Here's the test and its output: public class YWeatherReaderTest { public static final String[] rgDateSamples = { "Thu, 08 Apr 2010 12:20 PM CEST", "Thu, 08 Apr 2010 12:20 AM CEST" }; public void dateParsing() throws ParseException { DateFormat formatter = new SimpleDateFormat("EEE, dd MMM yyyy K:m a z", Locale.US); for (String dtsSrc : YWeatherReaderTest.rgDateSamples) { Date dt = formatter.parse(dtsSrc); String dtsDst = formatter.format(dt); System.out.println(dtsSrc); System.out.println(dtsDst); System.out.println(); } } } Thu, 08 Apr 2010 12:20 PM CEST Fri, 09 Apr 2010 0:20 AM CEST Thu, 08 Apr 2010 12:20 AM CEST Thu, 08 Apr 2010 0:20 PM CEST The second output line of the second iteration is slightly weird, because 00:20 isn't PM. The milliseconds value of the Date object, however, corresponds to the (wrong) time of 20 minutes past noon.

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  • iPhone static library Clang/LLVM error: non_lazy_symbol_pointers

    - by Bekenn
    After several hours of experimentation, I've managed to reduce the problem to the following example (C++): extern "C" void foo(); struct test { ~test() { } }; void doTest() { test t; // 1 foo(); // 2 } This is being compiled for iOS devices in XCode 4.2, using the provided Clang compiler (Apple LLVM compiler 3.0) and the iOS 5.0 SDK. The project is configured as a Cocoa Touch Static Library, and "Enable Linking With Shared Libraries" is set to No because I'm building an AIR native extension. The function foo is defined in another external library. (In my actual project, this would be any of the C API functions defined by Adobe for use in AIR native extensions.) When attempting to compile this code, I get back the error: FATAL:incompatible feature used: section type non_lazy_symbol_pointers (must specify "-dynamic" to be used) clang: error: assembler command failed with exit code 1 (use -v to see invocation) The error goes away if I comment out either of the lines marked 1 or 2 above, or if I change the build setting "Enable Linking With Shared Libraries" to Yes. (However, if I change the build setting, then I get multiple ld warning: unexpected srelocation type 9 warnings when linking the library into the final project, and the application crashes when running on the device.) The build error also goes away if I remove the destructor from test. So: Is this a bug in Clang? Am I missing some all-important and undocumented build setting? The interaction between an externally-provided function and a struct with a destructor is very peculiar, to say the least.

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  • Parsing basic math equations for children's educational software?

    - by Simucal
    Inspired by a recent TED talk, I want to write a small piece of educational software. The researcher created little miniature computers in the shape of blocks called "Siftables". [David Merril, inventor - with Siftables in the background.] There were many applications he used the blocks in but my favorite was when each block was a number or basic operation symbol. You could then re-arrange the blocks of numbers or operation symbols in a line, and it would display an answer on another siftable block. So, I've decided I wanted to implemented a software version of "Math Siftables" on a limited scale as my final project for a CS course I'm taking. What is the generally accepted way for parsing and interpreting a string of math expressions, and if they are valid, perform the operation? Is this a case where I should implement a full parser/lexer? I would imagine interpreting basic math expressions would be a semi-common problem in computer science so I'm looking for the right way to approach this. For example, if my Math Siftable blocks where arranged like: [1] [+] [2] This would be a valid sequence and I would perform the necessary operation to arrive at "3". However, if the child were to drag several operation blocks together such as: [2] [\] [\] [5] It would obviously be invalid. Ultimately, I want to be able to parse and interpret any number of chains of operations with the blocks that the user can drag together. Can anyone explain to me or point me to resources for parsing basic math expressions? I'd prefer as much of a language agnostic answer as possible.

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  • Data Mappers, Models and Images

    - by James
    Hi, I've seen and read plenty of blog posts and forum topics talking about and giving examples of Data Mapper / Model implementations in PHP, but I've not seen any that also deal with saving files/images. I'm currently working on a Zend Framework based project and I'm doing some image manipulation in the model (which is being passed a file path), and then I'm leaving it to the mapper to save that file to the appropriate location - is this common practise? But then, how do you deal with creating say 3 different size images from the one passed in? At the moment I have a "setImage($path_to_tmp_name)" which checks the image type, resizes and then saves back to the original filename. A call to "getImagePath()" then returns the current file path which the data mapper can use and then change with a call to "setImagePath($path)" once it's saved it to the appropriate location, say "/content/my_images". Does this sound practical to you? Also, how would you deal with getting the URL to that image? Do you see that as being something that the model should be providing? It seems to me like that model should worry about where the images are being stored or ultimately how they're accessed through a browser and so I'm inclined to put that in the ini file and just pass the URL prefix to the view through the controller. Does that sound reasonable? I'm using GD for image manipulation - not that that's of any relevance. UPDATE: I've been wondering if the image resizing should be done in the model at all. The model could require that it's provided a "main" image and a "thumb" image, both of certain dimensions. I've thought about creating a "getImageSpecs()" function in the model that would return something that defines the required sizes, then a separate image manipulation class could carry out the resizing and (perhaps in the controller?) and just pass the final paths in to the model using something like "setImagePaths($images)". Any thoughts much appreciated :) James.

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  • ADO.NET zombie transaction bug? How to ensure that commands will not be executed on implicit transac

    - by TN
    e.g. When deadlock occurs, following SQL commands are successfully executed, even if they have assigned SQL transaction that is after rollback. It seems, it is caused by a new implicit transaction that is created on SQL Server. Someone could expect that ADO.NET would throw an exception that the commands are being executed on a zombie transaction. However, such exception is not thrown. (I think this is a bug in ASP.NET.) Moreover, because of zombie transaction the final Dispose() silently ignores the rollback. Any ideas, how can I ensure that nobody can execute commands on implicit transaction? Or, how to check that transaction is zombie? I found that Commit() and Rollback() check for zombie transaction, however I can call them for a test:) I also found that also reading IsolationLevel will do the check, but I am not sure whether simple calling transaction.IsolationLevel.ToString(); will not be removed by a future optimizer. Or do you know any other safe way invoke a getter (without using reflection or IL emitting)?

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  • ADO/SQL Server: What is the error code for "timeout expired"?

    - by Ian Boyd
    i'm trying to trap a "timeout expired" error from ADO. When a timeout happens, ADO returns: Number: 0x80040E31 (DB_E_ABORTLIMITREACHED in oledberr.h) SQLState: HYT00 NativeError: 0 The NativeError of zero makes sense, since the timeout is not a function of the database engine (i.e. SQL Server), but of ADO's internal timeout mechanism. The Number (i.e. the COM hresult) looks useful, but the definition of DB_E_ABORTLIMITREACHED in oledberr.h says: Execution stopped because a resource limit was reached. No results were returned. This error could apply to things besides "timeout expired" (some potentially server-side), such as a governor that limits: CPU usage I/O reads/writes network bandwidth and stops a query. The final useful piece is SQLState, which is a database-independent error code system. Unfortunately the only reference for SQLState error codes i can find have no mention of HYT00. What to do? What do do? Note: i can't trust 0x80040E31 (DB_E_ABORTLIMITREACHED) to mean "timeout expired", anymore than i could trust 0x80004005 (E_UNSPECIFIED_ERROR) to mean "Transaction was deadlocked on lock resources with another process and has been chosen as the deadlock victim". My pseudo-question becomes: does anyone have documentation on what the SQLState "HYT000" means? And my real question still remains: How can i specifically trap an ADO timeout expired exception thrown by ADO? Gotta love the questions where the developer is trying to "do the right thing", but nobody knows how to do the right thing. Also gotta love how googling for DB_E_ABORTLIMITREACHED and this question is #9, with MSDN nowhere to be found. Update 3 From the OLEdb ICommand.Execute reference: DB_E_ABORTLIMITREACHED Execution has been aborted because a resource limit has been reached. For example, a query timed out. No results have been returned. "For example", meaning not an exhaustive list.

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  • How to make an entity out of a join table without primary key

    - by tputkonen
    I'm trying to generate JPA entities out of an existing database having an "interesting" design. Database has a table called UserSet, which can have links to several other UserSets. There is a one to many relation between UserSets and LinkedUserSets. LinkedUserSets also has one to one relation to UserSets. I tried to generate a JPA Entity out of the database structure using Dali JPA Tools. The resulting entity Linkeduserset misses @Id or @EmbeddedId annotation and thus failes to compile. As the resulting entity contains only two @JoinColumns (which cannot be marked as @Id), I have not so far found a way around this issue. Database structure can not be modified in any way. Is there a way to overcome this somehow? Relevant pars of create table statements: CREATE TABLE `LinkedUserSets` ( `UsrSetID` INT(11) NOT NULL DEFAULT '0' , `ChildID` INT(11) NOT NULL DEFAULT '0' , CONSTRAINT `fk_LinkedUserSets_UserSet1` FOREIGN KEY (`UsrSetID` ) REFERENCES `UserSet` (`UsrSetID` )); CREATE TABLE `UserSet` ( `UsrSetID` INT(11) NOT NULL AUTO_INCREMENT , PRIMARY KEY (`UsrSetID`), CONSTRAINT `fk_UserSet_LinkedUserSets1` FOREIGN KEY (`UsrSetID` ) REFERENCES `LinkedUserSets` (`ChildID` )); Generated entities: @Entity @Table(name="linkedusersets") public class Linkeduserset { //bi-directional many-to-one association to Userset @ManyToOne @JoinColumn(name="UsrSetID") private Userset userset1; //bi-directional one-to-one association to Userset @OneToOne @JoinColumn(name="ChildID") private Userset userset2; } @Entity @Table(name="userset") public class Userset { private static final long serialVersionUID = 1L; @Id @Column(name="UsrSetID") private int jngSetID; //bi-directional many-to-one association to Linkeduserset @OneToMany(mappedBy="userset1") private Set<Linkeduserset> linkedusersets; //bi-directional one-to-one association to Linkeduserset @OneToOne(mappedBy="userset2") private Linkeduserset linkeduserset; } Error message: Entity "Linkeduserset" has no Id or EmbeddedId

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  • How do I get the collection of Model State Errors in ASP.NET MVC?

    - by Ryan Montgomery
    How do I get the collection of errors in a view? I don't want to use the Html Helper Validation Summary or Validation Message. Instead I want to check for errors and if any display them in specific format. Also on the input controls I want to check for a specific property error and add a class to the input. P.S. I'm using the Spark View Engine but the idea should be the same. So I figured I could do something like... <if condition="${ModelState.Errors.Count > 0}"> DispalyErrorSummary() </if> ....and also... <input type="text" value="${Model.Name}" class="?{ModelState.Errors["Name"] != string.empty} error" /> .... Or something like that. UPDATE My final solution looked like this: <input type="text" value="${ViewData.Model.Name}" class="text error?{!ViewData.ModelState.IsValid && ViewData.ModelState["Name"].Errors.Count() > 0}" id="Name" name="Name" /> This only adds the error css class if this property has an error.

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  • Toggle row visibility one at a time

    - by kuswantin
    I have a couple of tables with similar structures like this: <table> <tbody> <tr>content</tr> <tr>content</tr> <tr>content</tr> <tr>content</tr> <tr>content</tr> <tr>content</tr> <tr>content</tr> <tr>content</tr> ..etc --- The fake button is added here <div class="addrow">Add another</div> </tbody> </table> Since this is a long list, I have a need to toggle the rows one at a time. I just need to show the first row, of course, the rest should be toggled. The action is when I click a dynamic fake button, it will show row no. 2, and clicking again will show another next row. This is what I have done so far: $("table#field_fruit_values tr.draggable").not(':first').hide(); $("table#field_vegetables_values tr.draggable").not(':first').hide(); $("body.form table.content-multiple-table tbody").append('<div class="addrow">Add</div>'); $(".addrow").click(function() { var hiddenRow = $(this).prev('tr.draggable'); $(this).prev(hiddenRow + 1).show(); //if (hiddenRow + ':last').length) { // <= silly logic // $(this).hide(); //} }); The button only works for one row. I must have done something wrong :) When the final is reached, I also want the button to disappear. Sorry if this question sound silly. Any help would be very much appreciated. Thanks.

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  • junit assert in thread throws exception

    - by antony.trupe
    What am I doing wrong that an exception is thrown instead of showing a failure, or should I not have assertions inside threads? @Test public void testComplex() throws InterruptedException { int loops = 10; for (int i = 0; i < loops; i++) { final int j = i; new Thread() { @Override public void run() { ApiProxy.setEnvironmentForCurrentThread(env);//ignore this new CounterFactory().getCounter("test").increment();//ignore this too int count2 = new CounterFactory().getCounter("test").getCount();//ignore assertEquals(j, count2);//here be exceptions thrown. this is line 75 } }.start(); } Thread.sleep(5 * 1000); assertEquals(loops, new CounterFactory().getCounter("test").getCount()); } StackTrace Exception in thread "Thread-26" junit.framework.AssertionFailedError: expected:<5> but was:<6> at junit.framework.Assert.fail(Assert.java:47) at junit.framework.Assert.failNotEquals(Assert.java:277) at junit.framework.Assert.assertEquals(Assert.java:64) at junit.framework.Assert.assertEquals(Assert.java:195) at junit.framework.Assert.assertEquals(Assert.java:201) at com.bitdual.server.dao.ShardedCounterTest$3.run(ShardedCounterTest.java:77)

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  • Optimizing processing and management of large Java data arrays

    - by mikera
    I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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  • php -Merging an Array

    - by Vidhu Shresth Bhatnagar
    I have two array which i want to merge in a specific way in php. So i need your help in helping me with it as i tried and failed. So say i have two arrays: $array1= array( "foo" => 3, "bar" => 2, "random1" => 4, ); $array2= array( "random2" => 3, "random3" => 4, "foo" => 6, ); Now when during merging i would like the common key's values to be added. So like foo exists in array1 and in array2 so when merging array1 with array 2 i should get "foo" => "9" I better illustration would be the final array which looks like this: $array1= array( "foo" => 9, "bar" => 2, "random1" => 4, "random2" => 3, "random3" => 4, ); So again i would like the values of the common keys to be added together and non common keys to be added to array or a new array I hope i was clear enough Thanks, Vidhu

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  • Data Flow Object Graph and An Execution Engine for it

    - by M Dotnet
    I would like to build a custom workflow engine from scratch. The input to this workflow is a data flow diagram which is composed of a series of activities connected together through lines where each each represent the data flow. Each activity can export multiple outputs. Activities are complex math functions but the logic is hidden from the user. My workflow engine job is to execute the given data flow diagram. Each activity within the data flow diagram is a custom activity and each activity can output different outputs. How do you suggest to model the data flow diagram object? I need to be able to construct the data flow diagram problematically (no need for drag and drop) but I need to display the final result graphically (for display and debugging purposes). Are there any libraries out there that I could use? Should I keep the workflow presentable as an xml? I know that there are many projects out there trying to essentially doing similar thing by building such workflow engines but I need something light weight and open source. I do not need any state machine execution engine and mine is primarily sequential workflow with fork and join capabilities. My activities are wrappable as basic C# classes and I do NOT want to use anything as heavy as .NET workflow foundation.

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  • PHP: Recursively get children of parent

    - by Nic Hubbard
    I have a function which gets the ids of all children of a parent from my DB. So, if I looked up id 7, it might return an array with 5, 6 and 10. What I then want to do, is recursively find the children of those returned ids, and so on, to the final depth of the children. I have tried to write a function to do this, but I am getting confused about recursion. function getChildren($parent_id) { $tree = Array(); $tree_string; if (!empty($parent_id)) { // getOneLevel() returns a one-dimentional array of child ids $tree = $this->getOneLevel($parent_id); foreach ($tree as $key => $val) { $ids = $this->getChildren($val); array_push($tree, $ids); //$tree[] = $this->getChildren($val); $tree_string .= implode(',', $tree); } return $tree_string; } else { return $tree; } }//end getChildren() After the function is run, I would like it to return a one-dimentional array of all the child ids that were found.

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  • what libraries or platforms should I use to build web apps that provide real-time, asynchronous data

    - by Daniel Sterling
    This is a less a question with a simple, practical answer and more a question to foster discussion on the real-time data exchange topic. I'll begin with an example: Google Wave is, at its core, a real-time asynchronous data synchronization engine. Wave supports (or plans to support) concurrent (real-time) document collaboration, disconnected (offline) document editing, conflict resolution, document history and playback with attribution, and server federation. A core part of Wave is the Operational Transformation engine: http://www.waveprotocol.org/whitepapers/operational-transform The OT engine manages document state. Changes between clients are merged and each client has a sane and consistent view of the document at all times; the final document is eventually consistent between all connected clients. My question is: is this system abstract or general enough to be used as a library or generic framework upon which to build web apps that synchronize real-time, asynchronous state in each client? Is the Wave protocol directly used by any current web applications (besides Google's client)? Would it make sense to directly use it for generic state synchronization in a web app? What other existing libraries or frameworks would you consider using when building such a web app? How much code in such an app might be domain-specific logic vs generic state synchronization logic? Or, put another way, how leaky might the state synchronization abstractions be? Comments and discussion welcomed!

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  • NotFoundException in layout editor for Android?

    - by borg17of20
    I'm trying to extend a RelativeLayout object and include an embedded SurfaceView object that uses a png file in my /res/drawable folder as its background but I keep getting an error in the XML Layout editor. See the following code: public class StopMotionRelativeLayout extends RelativeLayout { private Context myContext; private SurfaceView surfaceView1; private BitmapFactory.Options myBitmapOptions; private final android.view.ViewGroup.LayoutParams params = new LayoutParams(LayoutParams.FILL_PARENT, android.view.ViewGroup.LayoutParams.FILL_PARENT); public StopMotionRelativeLayout(Context context, AttributeSet attrs) { super(context, attrs); myContext = context; this.setBackgroundColor(Color.GREEN); //init images surfaceView1 = new SurfaceView(myContext,attrs); surfaceView1.setVisibility(View.INVISIBLE); this.addView(surfaceView1, params); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); myBitmapOptions = new Options(); myBitmapOptions.outWidth = widthMeasureSpec; myBitmapOptions.outHeight = heightMeasureSpec; surfaceView1.setBackgroundDrawable(new BitmapDrawable(BitmapFactory.decodeResource(this.myContext.getResources(), R.drawable.golf1, myBitmapOptions))); } } I get the following error: NotFoundException: Could not find drawable resource matching value 0x7F020002 (resolved name: golf1) in current configuration. I have seen this type of error may times now and it always happens when I try to load something from a resource file via code and not XML. Curiously, this error does not stop me from compiling the app, and the app runs without error in the emulator. I'd like to get back the use of my layout editor though... Please help. UPDATE: Here is the layout XML <?xml version="1.0" encoding="utf-8"?> <com.games.test.StopMotionRelativeLayout android:id="@+id/RelativeLayout01" android:layout_width="fill_parent" android:layout_height="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android"> </com.games.test.StopMotionRelativeLayout>

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