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• Why not Green Threads?

  - by redjamjar

  Whilst I know questions on this have been covered already (e.g. http://stackoverflow.com/questions/5713142/green-threads-vs-non-green-threads), I don't feel like I've got a satisfactory answer. The question is: why don't JVM's support green threads anymore? It says this on the code-style Java FAQ: A green thread refers to a mode of operation for the Java Virtual Machine (JVM) in which all code is executed in a single operating system thread. And this over on java.sun.com: The downside is that using green threads means system threads on Linux are not taken advantage of and so the Java virtual machine is not scalable when additional CPUs are added. It seems to me that the JVM could have a pool of system processes equal to the number of cores, and then run green threads on top of that. This could offer some big advantages when you have a very number large of threads which block often (mostly because current JVM's cap the number of threads). Thoughts?

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• Can I implement the readers and writers algorithm in OpenMP by replacing counting semaphores with another feature?

  - by DeveloperDon

  After reading about OpenMP and not finding functions to support semaphores, I did an internet search for OpenMP and the readers and writers problem, but found no suitable matches. Is there a general method for replacing counting semaphores in OpenMP with something that it supports? Or is there just a gap in the environment where it does not permit things that are asymmetrical like the third readers and writers problem shown on the following page? http://en.wikipedia.org/wiki/Readers-writers_problem#The_third_readers-writers_problem

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• What are the consequences of immutable classes with references to mutable classes?

  - by glenviewjeff

  I've recently begun adopting the best practice of designing my classes to be immutable per Effective Java [Bloch2008]. I have a series of interrelated questions about degrees of mutability and their consequences. I have run into situations where a (Java) class I implemented is only "internally immutable" because it uses references to other mutable classes. In this case, the class under development appears from the external environment to have state. Do any of the benefits (see below) of immutable classes hold true even by only "internally immutable" classes? Is there an accepted term for the aforementioned "internal mutability"? Wikipedia's immutable object page uses the unsourced term "deep immutability" to describe an object whose references are also immutable. Is the distinction between mutability and side-effect-ness/state important? Josh Bloch lists the following benefits of immutable classes: are simple to construct, test, and use are automatically thread-safe and have no synchronization issues do not need a copy constructor do not need an implementation of clone allow hashCode to use lazy initialization, and to cache its return value do not need to be copied defensively when used as a field make good Map keys and Set elements (these objects must not change state while in the collection) have their class invariant established once upon construction, and it never needs to be checked again always have "failure atomicity" (a term used by Joshua Bloch) : if an immutable object throws an exception, it's never left in an undesirable or indeterminate state

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• What happened to GremCheck? Is there a viable replacement?

  - by goober

  I was a big fan of an app called "GremCheck" that was out a while back, that seems to have disappeared. It was a JavaScript included in a master page that placed an icon at the bottom of the page. It was used during testing. You could define your own tests, and the box could pop up per page and viewers would answer the questions you define (such as "Does this page have the correct title?", "Is the Grammar Correct", "Does the design look consistent"). This was useful for end-user tests groups and quick testing for developers if time was squeezed on full functional testing. Anyone know where GremCheck went, if I can get to it, and if there's anything out there that does something similar?

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• Best way to deal with a system without a user acceptance / testing phase

  - by billy.bob

  Historically I've been able to get away with making small changes to an in-house helpdesk system riding on a LAMP stack and just making a backup prior to editing. This has no user acceptance / testing phase and I work on the live .php files directly. However now the requirement has arisen that will require a bit more coding done, and I'm obviously not particularly happy about making these changes without a framework to support me. What would the best way forward be? I could just make another backup I suppose.

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• How can QA prevent defects?

  - by user970696

  Also according to Software Testing By Srinisvasan Desikan, Gopalaswamy Ramesh or ISTQB text books. Quality assurance is e.g. reviewing products, inspections, walkthroughs to see if all standards are being followed. This is preventive activity. I cannot see how this can be preventive? For the references: defect prevention (Quality Assurance) Software Testing By Srinisvasan Desikan, Gopalaswamy Ramesh Quality Assurance (QA) tries to go one step further. Instead of concentrating on post- facto defect detection and correction, it focusses on the prevention of defects from the very start. Managing Global Software Projects - Page 110 QA deals with prevention of defects in the product being developed. Software Testing and Quality Assurance

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• What are the relative merits for implementing an Erlang-style "Continuation" pattern in C#

  - by JoeGeeky

  What are the relative merits (or demerits) for implementing an Erlang-style "Continuation" pattern in C#. I'm working on a project that has a large number of Lowest priority threads and I'm wondering if my approach may be all wrong. It would seem there is a reasonable upper limit to the number of long-running threads that any one Process 'should' spawn. With that said, I'm not sure what would signal the tipping-point for too many thread or when alternate patterns such as "Continuation" would be more suitable. In this case, many of the threads do a small amount of work and then sleep until woken to go again (Ex. Heartbeat, purge caches, etc...). This continues for the life of the Process.

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• Should developers be responsible for tests other than unit tests?

  - by Jackie

  I am currently working on a rather large project, and I have used JUnit and EasyMock to fairly extensively unit test functionality. I am now interested in what other types of testing I should worry about. As a developer is it my responsibility to worry about things like functional, or regression testing? Is there a good way to integrate these in a useable way in tools such as Maven/Ant/Gradle? Are these better suited for a Tester or BA? Are there other useful types of testing that I am missing?

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• Onsite Testing for Partners at Oracle OpenWorld San Francisco 2012

  - by Paul Sorensen

  If your company is a member of the Oracle PartnerNetwork Exchange, then you'll want to earn your certification and become Oracle Specialized by participating in the special Test Fest at the Oracle OpenWorld San Francisco 2012. The Oracle PartnerNetwork team has provided the following video with additional information about this fantastic opportunity. Ten sessions will be held during the conference.  Visit this PartnerNetwork Exchange web page for detailed information. You can see the testing session schedule, check out prep materials and get pre-registered to take your exam. If you are an employee of one of Oracle's partner companies (especially the PartnerNetwork Exchange) we hope that you will take advantage of this great opportunity to earn an Oracle certification!

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• Links for PrDC10 Session Visual Studio 2010 Testing Tools

  - by Aaron Kowall

  Here are the links I promised to post from my session on Visual Studio 2010 Testing Tools. To download and configure the TFS 2010 Virtual Machine the best instructions are here: http://blogs.msdn.com/b/briankel/archive/2010/03/18/now-available-visual-studio-2010-release-candidate-virtual-machines-with-sample-data-and-hands-on-labs.aspx To download and configure the Lab Management Virtual Machine, the best instructions are here: http://blogs.msdn.com/b/lab_management/archive/2010/02/12/one-box-lab-management-walkthrough.aspx Thanks to all that attended my presentation!  Hope you learned a bit. Technorati Tags: PrDC10,TFS 2010,VHD,Lab Management

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• UML Diagrams of Multi-Threaded Applications

  - by PersonalNexus

  For single-threaded applications I like to use class diagrams to get an overview of the architecture of that application. This type of diagram, however, hasn’t been very helpful when trying to understand heavily multi-threaded/concurrent applications, for instance because different instances of a class "live" on different threads (meaning accessing an instance is save only from the one thread it lives on). Consequently, associations between classes don’t necessarily mean that I can call methods on those objects, but instead I have to make that call on the target object's thread. Most literature I have dug up on the topic such as Designing Concurrent, Distributed, and Real-Time Applications with UML by Hassan Gomaa had some nice ideas, such as drawing thread boundaries into object diagrams, but overall seemed a bit too academic and wordy to be really useful. I don’t want to use these diagrams as a high-level view of the problem domain, but rather as a detailed description of my classes/objects, their interactions and the limitations due to thread-boundaries I mentioned above. I would therefore like to know: What types of diagrams have you found to be most helpful in understanding multi-threaded applications? Are there any extensions to classic UML that take into account the peculiarities of multi-threaded applications, e.g. through annotations illustrating that some objects might live in a certain thread while others have no thread-affinity; some fields of an object may be read from any thread, but written to only from one; some methods are synchronous and return a result while others are asynchronous that get requests queued up and return results for instance via a callback on a different thread.

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• Why should most logic be in the monitor objects and not in the thread objects when writing concurrent software in Java?

  - by refuser

  When I took the Realtime and Concurrent programming course our lecturer told us that when writing concurrent programs in Java and using monitors, most of the logic should be in the monitor and as little as possible in the threads that access it. I never really understood why and I really would like to. Let me clarify. In this particular case we had several classes. Lift extends Thread Person extends Thread LiftView Monitor, all methods synchronized. This is nothing we came up with, our task was to implement a lift simulation with persons waiting on different floors, and theses were the class skeletons that were given. Then our lecturer said to implement most of the logic in the monitor (he was talking about class Monitor as THE monitor) and as little as possible in the threads. Why would he make a statement like that?

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• Browser testing - Ideas on how to tackle it efficiently

  - by Rob

  Browser testing, the bane of any web designers life! Are there any tools and/or ways in which I can efficiently test different browsers on both Mac and PC? I not only want to test different browsers but also different versions of each browser. My current setup is on a Mac running VirtualBox with Windows Vista installed. This allows me to test both Mac and PC but the complications arise when trying to test different versions of browsers. Any one have any ideas?

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• How to improve testing your own code

  - by Peter

  Today I checked in a change on some code which turned out to be not working at all due to something rather stupid yet very crucial. I feel really bad about it and I hope I finally learn something from it. The stupid thing is, I've done these things before and I always tell myself, next time I won't be so stupid... Then it happens again and I feel even worse about it. I know you should keep your chin up and learn from your mistakes but here's the thing: I try to improve myself, I just don't see how I can prevent these things from happening. So, now I'm asking you guys: Do you have certain groundrules when testing your code?

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• Discussion of a Distributed Data Storage implementation

  - by fegol

  I want to implement a distributed data storage using a client/server architecture. Each data item will be stored persistently in disk in one of several remote servers. The client uses a library to update and query the data, shielding the client from its actual location. This should allow a client to associate keys (String) to values(byte[]), much as a Map does. The system must ensure that the amount of data stored in each server is approximately the same. The set of servers is known beforehand by other servers and clients. Both the client and the server will be written in Java, using sockets, threads, and files. I open this topic with the objective of discussing the best way to implement this idea, assuming simplicity, what are the issues of this implementation, performance measurements and discussion of the limitations.

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• Help me understand a part of Java Language Specification

  - by Software Engeneering Learner

  I'm reading part 17.2.1 of Java language specification: http://docs.oracle.com/javase/specs/jls/se7/html/jls-17.html#jls-17.2.1 I won't copy a text, it's too long, but I would like to know, why for third step of sequence they're saying that If thread t was removed from m's wait set in step 2 due to an interrupt Thread couldn't get to step 2 it wasn't removed from wait set, because it written for the step 1: Thread t does not execute any further instructions until it has been removed from m's wait set Thus thread can't be removed from wait set in step 2 whatever it's due to, because it was already removed. Please help me understand this.

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• How can I make a universal construction more efficient?

  - by VF1

  A "universal construction" is a wrapper class for a sequential object that enables it to be linearized (a strong consistency condition for concurrent objects). For instance, here's an adapted wait-free construction, in Java, from [1], which presumes the existence of a wait-free queue that satisfies the interface WFQ (which only requires one-time consensus between threads) and assumes a Sequential interface: public interface WFQ<T> // "FIFO" iteration { int enqueue(T t); // returns the sequence number of t Iterable<T> iterateUntil(int max); // iterates until sequence max } public interface Sequential { // Apply an invocation (method + arguments) // and get a response (return value + state) Response apply(Invocation i); } public interface Factory<T> { T generate(); } // generate new default object public interface Universal extends Sequential {} public class SlowUniversal implements Universal { Factory<? extends Sequential> generator; WFQ<Invocation> wfq = new WFQ<Invocation>(); Universal(Factory<? extends Sequential> g) { generator = g; } public Response apply(Invocation i) { int max = wfq.enqueue(i); Sequential s = generator.generate(); for(Invocation invoc : wfq.iterateUntil(max)) s.apply(invoc); return s.apply(i); } } This implementation isn't very satisfying, however, since it presumes determinism of a Sequential and is really slow. I attempted to add memory recycling: public interface WFQD<T> extends WFQ<T> { T dequeue(int n); } // dequeues only when n is the tail, else assists other threads public interface CopyableSequential extends Sequential { CopyableSequential copy(); } public class RecyclingUniversal implements Universal { WFQD<CopyableSequential> wfqd = new WFQD<CopyableSequential>(); Universal(CopyableSequential init) { wfqd.enqueue(init); } public Response apply(Invocation i) { int max = wfqd.enqueue(i); CopyableSequential cs = null; int ctr = max; for(CopyableSequential csq : wfq.iterateUntil(max)) if(--max == 0) cs = csq.copy(); wfqd.dequeue(max); return cs.apply(i); } } Here are my specific questions regarding the extension: Does my implementation create a linearizable multi-threaded version of a CopyableSequential? Is it possible extend memory recycling without extending the interface (perhaps my new methods trivialize the problem)? My implementation only reduces memory when a thread returns, so can this be strengthened? [1] provided an implementation for WFQ<T>, not WFQD<T> - one does exist, though, correct? [1] Herlihy and Shavit, The Art of Multiprocessor Programming.

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• Is QTWebKit still being actively developed? [closed]

  - by Brian M. Hunt

  I am considering recommending PhantomJS/CasperJS for a project, to provide continuous integration testing. Unfortunately those testing frameworks are based on QTWebKit, and it does not appear that there has been much activity on QTWebKit since September of 2011. It seems this is because of Nokia's financial troubles. QT has since been sold to Digia in August of this year, and can be found on qt.digia.com. It is not apparent whether QTWebKit will be actively developed. Before putting the effort into developing a PhantomJS/CasperJS testing framework, I would like to know whether the underlying QTWebKit framework is probably going to continue to be actively developed (or, alternatively, could be easily substituted with an alternative). I would suspect that since Digia just acquired QT it is a little too soon to tell what direction they will take the project. I would be interested in thoughts and comments on this issue.

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• What happened to GremCheck? Is there a viable replacement?

  - by goober

  [Cross-posted on StackOverflow, but thought it would receive a better response here. Thanks!] Hi all, I was a big fan of an app called "GremCheck" that was out a while back, that seems to have disappeared. It was a JavaScript included in a master page that placed an icon at the bottom of the page. It was used during testing. You could define your own tests, and the box could pop up per page and viewers would answer the questions you define (such as "Does this page have the correct title?", "Is the Grammar Correct", "Does the design look consistent"). This was useful for end-user tests groups and quick testing for developers if time was squeezed on full functional testing. Anyone know where GremCheck went, if I can get to it, and if there's anything out there that does something similar? Thanks for any help you can give!

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• Should developers be responsible for tests other than unit tests, if so which ones are the most common?

  - by Jackie

  I am currently working on a rather large project, and I have used JUnit and EasyMock to fairly extensively unit test functionality. I am now interested in what other types of testing I should worry about. As a developer is it my responsibility to worry about things like functional, or regression testing? Is there a good way to integrate these in a useable way in tools such as Maven/Ant/Gradle? Are these better suited for a Tester or BA? Are there other useful types of testing that I am missing?

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• XNA - Debugging/Testing Individual Sprites and Pixel Collision

  - by kwelch

  I ran through the first training on XNA where you make a shooter game. They did some thing that I would not do and I want to use their starting point to learn more things. I want to try better collision and adding a menu. I saw something online with the sonic physics where they have a frame by frame of sonic moving 1 pixel. See picture below. I am new to development, but I have been programming for years now. What would you guys suggest to try these different things out. How would I simulate a similar frame by frame testing as they do in the above picture? Thanks!

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• Mercurial release management. Rejecting changes that fail testing

  - by MYou

  Researching distributed source control management (specifically mercurial). My question is more or less what is the best practice for rejecting entire sets of code that fail testing? Example: A team is working on a hello world program. They have testers and a scheduled release coming up with specific features planned. Upcoming Release: Add feature A Add feature B Add feature C So, the developers make their clones for their features, do the work and merge them into a QA repo for the testers to scrutinize. Let's say the testers report back that "Feature B is incomplete and in fact dangerous", and they would like to retest A and C. End example. What's the best way to do all this so that feature B can easily be removed and you end up with a new repo that contains only feature A and C merged together? Recreate the test repo? Back out B? Other magic?

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• Testing what is happening inside your BizTalk solution

  - by Michael Stephenson

  As BizTalk developers we all know that one of the common challenges is how to test your BizTalk solution once it is deployed to BizTalk. Hopefully most of us are using the BizUnit framework for testing, but we still have the limitation that it's a very Black Box test. I have put together a sample and video to show a technique where I'm using the Logging Framework from the BizTalk CAT Team at Microsoft and where by BizUnit test is able to make assertions against the instrumentation going through the framework. This means that I can test for things happening such as the fact a component was executed or which branch of an orchestration was executed by simply using my normal instrumented code. I've put the sample and video for this on the following codeplex site: http://btsloggingeventsinbi.codeplex.com/ The video should also be on cloud casts fairly soon too.

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• Is it possible to test a theory?

  - by user363295

  We are a group of students who are working on a theory in software engineering (talking about the theory takes a lot of time so I just skip that). Implementing the theory is impossible, due to technical limitations, but it can be proven on a paper logically. We've been pushed to do a testing on it, so it can be proved that way too (although we bleieve that's not possible!), now: Basically, is it possible to test something like this? If it is, what type of testing should we use? I heard,its possible to handout a brief about it to some experts and asking about their opinion (not sure if that's true), is that a testing method? if it is, what does it called? and how exactly can be done?

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• Which parallel pattern to use?

  - by Wim Van Houts

  I need to write a server application that fetches mails from different mail servers/mailboxes and then needs to process/analyze these mails. Traditionally, I would do this multi-threaded, launching a thread for fetching mails (or maybe one per mailbox) and then process the mails. We are moving more and more to servers where we have 8+ cores, so I would like to make use of these cores as much as possible (and not use 1 at 100% and leave the seven others untouched). So conceptually, as an example, it would be nice that I could write the application in such a way that two cores are "continuously" fetching emails and four cores are "continuously" processing/analyzing the emails (since processing and analyzing mails is more CPU intensive than fetching mails). This seems like a good concept, but after studying some parallel patterns, I'm not really sure how this is best implemented. None of the patterns really fit. I'm working in VS2012, native C++, but I guess from a design point of view this does not really matter and just some pointers on how to organize this would be great!

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