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• IE9, HTML5 and truck load of other stuff happening around the web

  - by Harish Ranganathan

  First of all, I haven’t been updating this blog as regularly as it used to be.  Primarily, due to the fact was I was visiting a lot of cities talking about SharePoint, Web Matrix, IE9 and few other stuff.  IE9 is my new found love and I simply think we have done great work in improving the browser and browsing experiences for our users. This post would talk about IE, general things happening around the web and few misconceptions around IE (I had earlier written about IE8 and common myths When you think about the way web has transformed, its truly amazing.  Rewind back to late 90s and early 2000s, web was a luxury.  There were lot of desktop applications running around and web applications was starting to pick up.  Primarily reason was not a lot of folks were into web development and the areas of web were confined to HTML and JavaScript.  CSS was around here and there but no one took it so seriously.  XML, XSLT was fast picking up and contributed to decent web development techniques. So as a web developer all we had to worry about was, building good looking websites which worked well with IE6 and occasionally with Safari.  Firefox was  not even in the picture then and so was Chrome.  But with the various arms of W3C consortium and other bodies working actively on stuff like CSS, SVG and XHTML, few more areas came into picture when it comes to browsers supporting standards.  IE6 for sure wasn’t up to the speed and the main issue we were tackling then was privacy and piracy.  We did invest a lot of our efforts to curb piracy and one of the steps into it was that, IE7 the next version of IE would install only on genuine windows machines.  What this means, is that, people who were running pirated windows xp knowingly/unknowingly could not install IE7 and the limitations of IE6 really hurt them.  One more thing of importance is that, if you were running pirated windows, lots of chances that you didn’t get the security updates and thereby were vulnerable to run viruses/trojans on your system. Many of them actually block using IE in the first place and make it difficult to browse.  SP2 came as a big boon but again was there only for genuine windows machines. With Firefox coming as a free install and also heavily pushed by Google then, it was natural that people would try an alternative.  By then, we had started working on IE8 supporting the best standards (note HTML5, CSS 2.1 and other specs were then work in progress.  they are still) Later, Google in their infinite wisdom realized that with Firefox they were going nowhere and they released Chrome.  Now, they heavily push Chrome even for Firefox users, which is natural since its their browser. In the meanwhile, these browsers push their updates as mandatory and therefore have a very short lifecycle to add enhancements and support for stuff like CSS etc., Meanwhile, when IE8 came out, it really was the best standards supported browser and a lot of people saw our efforts in improving our browser. HTML5 is the buzz word in the industry and there is a lot of noise being made by many browsers claiming their support for it.  IE8 doesn’t have much support for HTML5.  But, with IE9 Beta, we have great support for many of HTML5 specifications.  Note that, HTML5 is still work under progress and one of the board of members working on the spec has mentioned that these specs might change and relying on them heavily is dangerous.  But, some of the advances such as video tag, etc., are indeed supported in IE9 Beta.  IE9 Beta also has full hardware acceleration support which other browsers don’t have. IE8 had advanced security features such as smartscreen filter, in-private browsing, anti-phishing and a lot of other stuff.  IE9 builds on top of these with the best in town security standards as well as support for HTML5, CSS3, Hardware acceleration, SVG and many other advancements in browser.  Read more at http://www.beautyoftheweb.com/#/highlights/html5  To summarize, IE9 Beta is really innovative and you should try it to believe what it provides.  You can visit http://www.beautyoftheweb.com/  to install as well as read more on this. Cheers !!!

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• Threading Overview

  - by ACShorten

  One of the major features of the batch framework is the ability to support multi-threading. The multi-threading support allows a site to increase throughput on an individual batch job by splitting the total workload across multiple individual threads. This means each thread has fine level control over a segment of the total data volume at any time. The idea behind the threading is based upon the notion that "many hands make light work". Each thread takes a segment of data in parallel and operates on that smaller set. The object identifier allocation algorithm built into the product randomly assigns keys to help ensure an even distribution of the numbers of records across the threads and to minimize resource and lock contention. The best way to visualize the concept of threading is to use a "pie" analogy. Imagine the total workset for a batch job is a "pie". If you split that pie into equal sized segments, each segment would represent an individual thread. The concept of threading has advantages and disadvantages: Smaller elapsed runtimes - Jobs that are multi-threaded finish earlier than jobs that are single threaded. With smaller amounts of work to do, jobs with threading will finish earlier. Note: The elapsed runtime of the threads is rarely proportional to the number of threads executed. Even though contention is minimized, some contention does exist for resources which can adversely affect runtime. Threads can be managed individually – Each thread can be started individually and can also be restarted individually in case of failure. If you need to rerun thread X then that is the only thread that needs to be resubmitted. Threading can be somewhat dynamic – The number of threads that are run on any instance can be varied as the thread number and thread limit are parameters passed to the job at runtime. They can also be configured using the configuration files outlined in this document and the relevant manuals.Note: Threading is not dynamic after the job has been submitted Failure risk due to data issues with threading is reduced – As mentioned earlier individual threads can be restarted in case of failure. This limits the risk to the total job if there is a data issue with a particular thread or a group of threads. Number of threads is not infinite – As with any resource there is a theoretical limit. While the thread limit can be up to 1000 threads, the number of threads you can physically execute will be limited by the CPU and IO resources available to the job at execution time. Theoretically with the objects identifiers evenly spread across the threads the elapsed runtime for the threads should all be the same. In other words, when executing in multiple threads theoretically all the threads should finish at the same time. Whilst this is possible, it is also possible that individual threads may take longer than other threads for the following reasons: Workloads within the threads are not always the same - Whilst each thread is operating on the roughly the same amounts of objects, the amount of processing for each object is not always the same. For example, an account may have a more complex rate which requires more processing or a meter has a complex amount of configuration to process. If a thread has a higher proportion of objects with complex processing it will take longer than a thread with simple processing. The amount of processing is dependent on the configuration of the individual data for the job. Data may be skewed – Even though the object identifier generation algorithm attempts to spread the object identifiers across threads there are some jobs that use additional factors to select records for processing. If any of those factors exhibit any data skew then certain threads may finish later. For example, if more accounts are allocated to a particular part of a schedule then threads in that schedule may finish later than other threads executed. Threading is important to the success of individual jobs. For more guidelines and techniques for optimizing threading refer to Multi-Threading Guidelines in the Batch Best Practices for Oracle Utilities Application Framework based products (Doc Id: 836362.1) whitepaper available from My Oracle Support

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• Synchronous Actions

  - by Dan Krasinski-Oracle

  Since the introduction of SMF, svcadm(1M) has had the ability to enable or disable a service instance and wait for that service instance to reach a final state.  With Oracle Solaris 11.2, we’ve expanded the set of administrative actions which can be invoked synchronously. Now all subcommands of svcadm(1M) have synchronous behavior. Let’s take a look at the new usage: Usage: svcadm [-v] [cmd [args ... ]] svcadm enable [-rt] [-s [-T timeout]] <service> ... enable and online service(s) svcadm disable [-t] [-s [-T timeout]] <service> ... disable and offline service(s) svcadm restart [-s [-T timeout]] <service> ... restart specified service(s) svcadm refresh [-s [-T timeout]] <service> ... re-read service configuration svcadm mark [-It] [-s [-T timeout]] <state> <service> ... set maintenance state svcadm clear [-s [-T timeout]] <service> ... clear maintenance state svcadm milestone [-d] [-s [-T timeout]] <milestone> advance to a service milestone svcadm delegate [-s] <restarter> <svc> ... delegate service to a restarter As you can see, each subcommand now has a ‘-s’ flag. That flag tells svcadm(1M) to wait for the subcommand to complete before returning. For enables, that means waiting until the instance is either ‘online’ or in the ‘maintenance’ state. For disable, the instance must reach the ‘disabled’ state. Other subcommands complete when: restart A restart is considered complete once the instance has gone offline after running the ‘stop’ method, and then has either returned to the ‘online’ state or has entered the ‘maintenance’ state. refresh If an instance is in the ‘online’ state, a refresh is considered complete once the ‘refresh’ method for the instance has finished. mark maintenance Marking an instance for maintenance completes when the instance has reached the ‘maintenance’ state. mark degraded Marking an instance as degraded completes when the instance has reached the ‘degraded’ state from the ‘online’ state. milestone A milestone transition can occur in one of two directions. Either the transition moves from a lower milestone to a higher one, or from a higher one to a lower one. When moving to a higher milestone, the transition is considered complete when the instance representing that milestone reaches the ‘online’ state. The transition to a lower milestone, on the other hand, completes only when all instances which are part of higher milestones have reached the ‘disabled’ state. That’s not the whole story. svcadm(1M) will also try to determine if the actions initiated by a particular subcommand cannot complete. Trying to enable an instance which does not have its dependencies satisfied, for example, will cause svcadm(1M) to terminate before that instance reaches the ‘online’ state. You’ll also notice the optional ‘-T’ flag which can be used in conjunction with the ‘-s’ flag. This flag sets a timeout, in seconds, after which svcadm gives up on waiting for the subcommand to complete and terminates. This is useful in many cases, but in particular when the start method for an instance has an infinite timeout but might get stuck waiting for some resource that may never become available. For the C-oriented, each of these administrative actions has a corresponding function in libscf(3SCF), with names like smf_enable_instance_synchronous(3SCF) and smf_restart_instance_synchronous(3SCF).  Take a look at smf_enable_instance_synchronous(3SCF) for details.

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• Feynman's inbox

  - by user12607414

  Here is Richard Feynman writing on the ease of criticizing theories, and the difficulty of forming them: The problem is not just to say something might be wrong, but to replace it by something — and that is not so easy. As soon as any really definite idea is substituted it becomes almost immediately apparent that it does not work. The second difficulty is that there is an infinite number of possibilities of these simple types. It is something like this. You are sitting working very hard, you have worked for a long time trying to open a safe. Then some Joe comes along who knows nothing about what you are doing, except that you are trying to open the safe. He says ‘Why don’t you try the combination 10:20:30?’ Because you are busy, you have tried a lot of things, maybe you have already tried 10:20:30. Maybe you know already that the middle number is 32 not 20. Maybe you know as a matter of fact that it is a five digit combination… So please do not send me any letters trying to tell me how the thing is going to work. I read them — I always read them to make sure that I have not already thought of what is suggested — but it takes too long to answer them, because they are usually in the class ‘try 10:20:30’. (“Seeking New Laws”, page 161 in The Character of Physical Law.) As a sometime designer (and longtime critic) of widely used computer systems, I have seen similar difficulties appear when anyone undertakes to publicly design a piece of software that may be used by many thousands of customers. (I have been on both sides of the fence, of course.) The design possibilities are endless, but the deep design problems are usually hidden beneath a mass of superfluous detail. The sheer numbers can be daunting. Even if only one customer out of a thousand feels a need to express a passionately held idea, it can take a long time to read all the mail. And it is a fact of life that many of those strong suggestions are only weakly supported by reason or evidence. Opinions are plentiful, but substantive research is time-consuming, and hence rare. A related phenomenon commonly seen with software is bike-shedding, where interlocutors focus on surface details like naming and syntax… or (come to think of it) like lock combinations. On the other hand, software is easier than quantum physics, and the population of people able to make substantial suggestions about software systems is several orders of magnitude bigger than Feynman’s circle of colleagues. My own work would be poorer without contributions — sometimes unsolicited, sometimes passionately urged on me — from the open source community. If a Nobel prize winner thought it was worthwhile to read his mail on the faint chance of learning a good idea, I am certainly not going to throw mine away. (In case anyone is still reading this, and is wondering what provoked a meditation on the quality of one’s inbox contents, I’ll simply point out that the volume has been very high, for many months, on the Lambda-Dev mailing list, where the next version of the Java language is being discussed. Bravo to those of my colleagues who are surfing that wave.) I started this note thinking there was an odd parallel between the life of the physicist and that of a software designer. On second thought, I’ll bet that is the story for anybody who works in public on something requiring special training. (And that would be pretty much anything worth doing.) In any case, Feynman saw it clearly and said it well.

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• Learn Many Languages

  - by Jeff Foster

  My previous blog, Deliberate Practice, discussed the need for developers to “sharpen their pencil” continually, by setting aside time to learn how to tackle problems in different ways. However, the Sapir-Whorf hypothesis, a contested and somewhat-controversial concept from language theory, seems to hold reasonably true when applied to programming languages. It states that: “The structure of a language affects the ways in which its speakers conceptualize their world.” If you’re constrained by a single programming language, the one that dominates your day job, then you only have the tools of that language at your disposal to think about and solve a problem. For example, if you’ve only ever worked with Java, you would never think of passing a function to a method. A good developer needs to learn many languages. You may never deploy them in production, you may never ship code with them, but by learning a new language, you’ll have new ideas that will transfer to your current “day-job” language. With the abundant choices in programming languages, how does one choose which to learn? Alan Perlis sums it up best. “A language that doesn‘t affect the way you think about programming is not worth knowing“ With that in mind, here’s a selection of languages that I think are worth learning and that have certainly changed the way I think about tackling programming problems. Clojure Clojure is a Lisp-based language running on the Java Virtual Machine. The unique property of Lisp is homoiconicity, which means that a Lisp program is a Lisp data structure, and vice-versa. Since we can treat Lisp programs as Lisp data structures, we can write our code generation in the same style as our code. This gives Lisp a uniquely powerful macro system, and makes it ideal for implementing domain specific languages. Clojure also makes software transactional memory a first-class citizen, giving us a new approach to concurrency and dealing with the problems of shared state. Haskell Haskell is a strongly typed, functional programming language. Haskell’s type system is far richer than C# or Java, and allows us to push more of our application logic to compile-time safety. If it compiles, it usually works! Haskell is also a lazy language – we can work with infinite data structures. For example, in a board game we can generate the complete game tree, even if there are billions of possibilities, because the values are computed only as they are needed. Erlang Erlang is a functional language with a strong emphasis on reliability. Erlang’s approach to concurrency uses message passing instead of shared variables, with strong support from both the language itself and the virtual machine. Processes are extremely lightweight, and garbage collection doesn’t require all processes to be paused at the same time, making it feasible for a single program to use millions of processes at once, all without the mental overhead of managing shared state. The Benefits of Multilingualism By studying new languages, even if you won’t ever get the chance to use them in production, you will find yourself open to new ideas and ways of coding in your main language. For example, studying Haskell has taught me that you can do so much more with types and has changed my programming style in C#. A type represents some state a program should have, and a type should not be able to represent an invalid state. I often find myself refactoring methods like this… void SomeMethod(bool doThis, bool doThat) { if (!(doThis ^ doThat)) throw new ArgumentException(“At least one arg should be true”); if (doThis) DoThis(); if (doThat) DoThat(); } …into a type-based solution, like this: enum Action { DoThis, DoThat, Both }; void SomeMethod(Action action) { if (action == Action.DoThis || action == Action.Both) DoThis(); if (action == Action.DoThat || action == Action.Both) DoThat(); } At this point, I’ve removed the runtime exception in favor of a compile-time check. This is a trivial example, but is just one of many ideas that I’ve taken from one language and implemented in another.

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• The long road to bug-free software

  - by Tony Davis

  The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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• Patterns for a tree of persistent data with multiple storage options?

  - by Robin Winslow

  I have a real-world problem which I'll try to abstract into an illustrative example. So imagine I have data objects in a tree, where parent objects can access children, and children can access parents: // Interfaces interface IParent<TChild> { List<TChild> Children; } interface IChild<TParent> { TParent Parent; } // Classes class Top : IParent<Middle> {} class Middle : IParent<Bottom>, IChild<Top> {} class Bottom : IChild<Middle> {} // Usage var top = new Top(); var middles = top.Children; // List<Middle> foreach (var middle in middles) { var bottoms = middle.Children; // List<Bottom> foreach (var bottom in bottoms) { var middle = bottom.Parent; // Access the parent var top = middle.Parent; // Access the grandparent } } All three data objects have properties that are persisted in two data stores (e.g. a database and a web service), and they need to reflect and synchronise with the stores. Some objects only request from the web service, some only write to it. Data Mapper My favourite pattern for data access is Data Mapper, because it completely separates the data objects themselves from the communication with the data store: class TopMapper { public Top FetchById(int id) { var top = new Top(DataStore.TopDataById(id)); top.Children = MiddleMapper.FetchForTop(Top); return Top; } } class MiddleMapper { public Middle FetchById(int id) { var middle = new Middle(DataStore.MiddleDataById(id)); middle.Parent = TopMapper.FetchForMiddle(middle); middle.Children = BottomMapper.FetchForMiddle(bottom); return middle; } } This way I can have one mapper per data store, and build the object from the mapper I want, and then save it back using the mapper I want. There is a circular reference here, but I guess that's not a problem because most languages can just store memory references to the objects, so there won't actually be infinite data. The problem with this is that every time I want to construct a new Top, Middle or Bottom, it needs to build the entire object tree within that object's Parent or Children property, with all the data store requests and memory usage that that entails. And in real life my tree is much bigger than the one represented here, so that's a problem. Requests in the object In this the objects request their Parents and Children themselves: class Middle { private List<Bottom> _children = null; // cache public List<Bottom> Children { get { _children = _children ?? BottomMapper.FetchForMiddle(this); return _children; } set { BottomMapper.UpdateForMiddle(this, value); _children = value; } } } I think this is an example of the repository pattern. Is that correct? This solution seems neat - the data only gets requested from the data store when you need it, and thereafter it's stored in the object if you want to request it again, avoiding a further request. However, I have two different data sources. There's a database, but there's also a web service, and I need to be able to create an object from the web service and save it back to the database and then request it again from the database and update the web service. This also makes me uneasy because the data objects themselves are no longer ignorant of the data source. We've introduced a new dependency, not to mention a circular dependency, making it harder to test. And the objects now mask their communication with the database. Other solutions Are there any other solutions which could take care of the multiple stores problem but also mean that I don't need to build / request all the data every time?

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• Application using JOGL stays in Limbo when closing

  - by Roy T.

  I'm writing a game using Java and OpenGL using the JOGL bindings. I noticed that my game doesn't terminate properly when closing the window even though I've set the closing operation of the JFrame to EXIT_ON_CLOSE. I couldn't track down where the problem was so I've made a small reproduction case. Note that on some computers the program terminates normally when closing the window but on other computers (notably my own) something in the JVM keeps lingering, this causes the JFrame to never be disposed and the application to never exit. I haven't found something in common between the computers that had difficulty terminating. All computers had Windows 7, Java 7 and the same version of JOGL and some terminated normally while others had this problem. The test case is as follows: public class App extends JFrame implements GLEventListener { private GLCanvas canvas; @Override public void display(GLAutoDrawable drawable) { GL3 gl = drawable.getGL().getGL3(); gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f); gl.glClear(GL3.GL_COLOR_BUFFER_BIT); gl.glFlush(); } // The overrides for dispose (the OpenGL one), init and reshape are empty public App(String title, boolean full_screen, int width, int height) { //snipped setting the width and height of the JFRAME GLProfile profile = GLProfile.get(GLProfile.GL3); GLCapabilities capabilities = new GLCapabilities(profile); canvas = new GLCanvas(capabilities); canvas.addGLEventListener(this); canvas.setSize(getWidth(), getHeight()); add(canvas); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //!!! setVisible(true); } @Override public void dispose() { System.out.println("HELP"); // } public static void main( String[] args ) { new App("gltut 01", false, 1280, 720); } } As you can see this doesn't do much more than adding a GLCanvas to the frame and registering the main class as the GLEventListener. So what keeps lingering? I'm not sure. I've made some screenshots. The application running normally. The application after the JFrame is closed, note that the JVM still hasn't exited or printed a return code. The application after it was force closed. Note the return code -1, so it wasnt just the JVM standing by or something the application really hadn't exited yet. So what is keeping the application in Limbo? Might it be the circular reference between the GLCanvas and the JFrame? I thought the GC could figure that out. If so how should I deal with that when I want to exit? Is there any other clean-up required when using JOGL? I've tried searching but it doesn't seem to be necessary. Edit, to clarify: there are 2 dispose functions dispose(GLAutoDrawable arg) which is a member of GLEventListener and dispose() which is a member of JFrame. The first one is called correctly (but I wouldn't know what to there, destroying the GLAutoDrawable or the GLCanvas gives an infinite exception loop) the second one is never called.

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• The long road to bug-free software

  - by Tony Davis

  The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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• Why does OpenGL seem to ignore my glBindTexture call?

  - by Killrazor

  I'm having problems making a simple sprite rendering. I load 2 different textures. Then, I bind these textures and draw 2 squares, one with each texture. But only the texture of the first rendered object is drawn in both squares. Its like if I'd only use a texture or as if glBindTexture don't work properly. I know that GL is a state machine, but I think that you only need to change active texture with glBindTexture. I load texture with this method: bool CTexture::generate( utils::CImageBuff* img ) { assert(img); m_image = img; CHECKGL(glGenTextures(1,&m_textureID)); CHECKGL(glBindTexture(GL_TEXTURE_2D,m_textureID)); CHECKGL(glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR)); CHECKGL(glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR)); //CHECKGL(glTexImage2D(GL_TEXTURE_2D,0,img->getBpp(),img->getWitdh(),img->getHeight(),0,img->getFormat(),GL_UNSIGNED_BYTE,img->getImgData())); CHECKGL(glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, img->getWitdh(), img->getHeight(), 0, GL_RGBA, GL_UNSIGNED_BYTE, img->getImgData())); return true; } And I bind textures with this function: void CTexture::bind() { CHECKGL(glBindTexture(GL_TEXTURE_2D,m_textureID)); } Also, I draw sprites with this method void CSprite2D::render() { CHECKGL(glLoadIdentity()); CHECKGL(glEnable(GL_TEXTURE_2D)); CHECKGL(glEnable(GL_BLEND)); CHECKGL(glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)); m_texture->bind(); CHECKGL(glPushMatrix()); CHECKGL(glBegin(GL_QUADS)); CHECKGL(glTexCoord2f(m_textureAreaStart.s,m_textureAreaStart.t)); // 0,0 by default CHECKGL(glVertex3i(m_position.x,m_position.y,0)); CHECKGL(glTexCoord2f(m_textureAreaEnd.s,m_textureAreaStart.t)); // 1,0 by default CHECKGL(glVertex3i( m_position.x + m_dimensions.x, m_position.y, 0)); CHECKGL(glTexCoord2f(m_textureAreaEnd.s, m_textureAreaEnd.t)); // 1,1 by default CHECKGL(glVertex3i( m_position.x + m_dimensions.x, m_position.y + m_dimensions.y, 0)); CHECKGL(glTexCoord2f(m_textureAreaStart.s, m_textureAreaEnd.t)); // 0,1 by default CHECKGL(glVertex3i( m_position.x, m_position.y + m_dimensions.y,0)); CHECKGL(glPopMatrix()); CHECKGL(glDisable(GL_BLEND)); } Edit: I bring also the check error code: int CheckGLError(const char *GLcall, const char *file, int line) { GLenum errCode; //avoids infinite loop int errorCount = 0; while ( (errCode=glGetError()) != GL_NO_ERROR && ++errorCount < 3000) { utils::globalLogPtr log = utils::CGLogFactory::getLogInstance(); const GLubyte *errString; errString = gluErrorString(errCode); std::stringstream ss; ss << "In "<< __FILE__<<"("<< __LINE__<<") "<<"GL error with code: " << errCode<<" at file " << file << ", line " << line << " with message: " << errString << "\n"; log->addMessage(ss.str(),ZEL_APPENDER_GL,utils::LOGLEVEL_ERROR); } return 0; }

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• Access to bound data in IMultiValueConverter.ConvertBack() in C#/WPF

  - by absence

  I have a problem with a multibinding: <Canvas> <local:SPoint x:Name="sp" Width="10" Height="10"> <Canvas.Left><!-- irrelevant binding here --></Canvas.Left> <Canvas.Top> <MultiBinding Converter="{StaticResource myConverter}" Mode="TwoWay"> <Binding ElementName="cp1" Path="(Canvas.Top)"/> <Binding ElementName="cp1" Path="Height"/> <Binding ElementName="cp2" Path="(Canvas.Top)"/> <Binding ElementName="cp2" Path="Height"/> <Binding ElementName="sp" Path="Height"/> <Binding ElementName="sp" Path="Slope" Mode="TwoWay"/> </MultiBinding> </Canvas.Top> </local:SPoint> <local:CPoint x:Name="cp1" Width="10" Height="10" Canvas.Left="20" Canvas.Top="150"/> <local:CPoint x:Name="cp2" Width="10" Height="10" Canvas.Left="100" Canvas.Top="20"/> </Canvas> In order to calculate the Canvas.Top value, myConverter needs all the bound values. This works great in Convert(). Going the other way, myConverter should ideally calculate the Slope value (Binding.DoNothing for the rest), but it needs the other values in addition to the Canvas.Top one passed to ConvertBack(). What is the right way to solve this? I have tried making the binding OneWay and create an additional multibinding for local:SPoint.Slope, but that causes infinite recursion and stack overflow. I was thinking the ConverterParameter could be used, but it seems like it's not possible to bind to it.

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• Streaming to the Android MediaPlayer

  - by Rob Szumlakowski

  Hi. I'm trying to write a light-weight HTTP server in my app to feed dynamically generated MP3 data to the built-in Android MediaPlayer. I am not permitted to store my content on the SD card. My input data is essentially of an infinite length. I tell MediaPlayer that its data source should basically be something like "http://localhost/myfile.mp3". I've a simple server set up that waits for MediaPlayer to make this request. However, MediaPlayer isn't very cooperative. At first, it makes an HTTP GET and tries to grab the whole file. It times out if we try and simply dump data into the socket so we tried using the HTTP Range header to write data in chunks. MediaPlayer doesn't like this and doesn't keep requesting the subsequent chunks. Has anyone had any success streaming data directly into MediaPlayer? Do I need to implement an RTSP or Shoutcast server instead? Am I simply missing a critical HTTP header? What strategy should I use here? Rob Szumlakowski

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• Code Golf: Collatz Conjecture

  - by Earlz

  Inspired by http://xkcd.com/710/ here is a code golf for it. The Challenge Given a positive integer greater than 0, print out the hailstone sequence for that number. The Hailstone Sequence See Wikipedia for more detail.. If the number is even, divide it by two. If the number is odd, triple it and add one. Repeat this with the number produced until it reaches 1. (if it continues after 1, it will go in an infinite loop of 1 -> 4 -> 2 -> 1...) Sometimes code is the best way to explain, so here is some from Wikipedia function collatz(n) show n if n > 1 if n is odd call collatz(3n + 1) else call collatz(n / 2) This code works, but I am adding on an extra challenge. The program must not be vulnerable to stack overflows. So it must either use iteration or tail recursion. Also, bonus points for if it can calculate big numbers and the language does not already have it implemented. (or if you reimplement big number support using fixed-length integers) Test case Number: 21 Results: 21 -> 64 -> 32 -> 16 -> 8 -> 4 -> 2 -> 1 Number: 3 Results: 3 -> 10 -> 5 -> 16 -> 8 -> 4 -> 2 -> 1 Also, the code golf must include full user input and output.

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• JavaScript - Settting property on Object in Image load function, property not set once outside funct

  - by Sunday Ironfoot

  Sometimes JavaScript doesn't make sense to me, consider the following code that generates a photo mosaic based on x/y tiles. I'm trying to set a .Done property to true once each Mosaic image has been downloaded, but it's always false for some reason, what am I doing wrong? var tileData = []; function generate() { var image = new Image(); image.onload = function() { // Build up the 'tileData' array with tile objects from this Image for (var i = 0; i < tileData.length; i++) { var tile = tileData[i]; var tileImage = new Image(); tileImage.onload = function() { // Do something with this tile Image tile.Done = true; }; tileImage.src = tile.ImageUrl; } }; image.src = 'Penguins.jpg'; tryDisplayMosaic(); } function tryDisplayMosaic() { setTimeout(function() { for (var i = 0; i < tileData.length; i++) { var tile = tileData[i]; if (!tile.Done) { tryDisplayMosaic(); return; } } // If we get here then all the tiles have been downloaded alert('All images downloaded'); }, 2000); } Now for some reason the .Done property on the tile object is always false, even though it is explicitly being set to true inside tileImage.onload = function(). And I can ensure you that this function DOES get called because I've placed an alert() call inside it. Right now it's just stuck inside an infinite loop calling tryDisplayMosaic() constantly. Also if I place a loop just before tryDisplayMosaic() is called, and in that loop I set .Done = true, then .Done property is true and alert('All images downloaded'); will get called.

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• [Gray Hat Python] Simple debugger, want work ??

  - by Rami Jarrar

  hi, i'm reading the Gray Hat Python,, i reach for this :: class debugger(): def __init__(self): self.h_process = None self.pid = None self.debugger_active = False def load(self,path_to_exe): creation_flags = DEBUG_PROCESS startupinfo = STARTUPINFO() process_information = PROCESS_INFORMATION() startupinfo.dwFlags = 0x1 startupinfo.wShowWindows = 0x0 startupinfo.cb = sizeof(startupinfo) if kernel32.CreateProcessA(path_to_exe, None, None, None, None, creation_flags, None, None, byref(startupinfo), byref(process_information)): print "[*] We have successfully launched the process!" print "[*] PID: %d"%(process_information.dwProcessId) self.h_process = self.open_process(process_information.dwProcessId) else: print "[*] Error: 0x%08x."%(kernel32.GetLastError()) def open_process(self,pid): h_process = self.open_process(pid) if kernel32.DebugActiveProcess(pid): self.debugger_active = True self.pid = int(pid) self.run() else: print "[*] Unable to attach to the process." def run(self): while self.debugger_active == True: self.get_debug_event() def get_debug_event(self): debug_event = DEBUG_EVENT() continue_status = DBG_CONTINUE if kernel32.WaitForDebugEvent(byref(debug_event), INFINITE): raw_input("Press a Key to continue...") self.debugger_active = False kernel32.ContinueDebugEvent( \ debug_event.dwProcessId, \ debug_event.dwThreadId, \ continue_status ) def detach(self): if kernel32.DebugActiveProcessStop(self.pid): print "[*] Finished debugging. Exiting..." return True else: print "There was an error" return False when run my_test.py :: import my_dbg debugger = my_dbg.debugger() pid = raw_input('Enter the PID of the process to attach to: ') debugger.open_process(int(pid)) debugger.detach() i get this error :: Traceback (most recent call last): File "C:/Python26/dbgpy/my_test.py", line 5, in <module> debugger.attach(int(pid)) File "C:/Python26/dbgpy\my_dbg.py", line 37, in attach h_process = self.attach(pid) ........... ........... ........... File "C:/Python26/dbgpy\my_dbg.py", line 37, in attach h_process = self.attach(pid) File "C:/Python26/dbgpy\my_dbg.py", line 37, in attach h_process = self.attach(pid) RuntimeError: maximum recursion depth exceeded its because the loop and something else, but what it is ?? I'm running on Windows using Python2.6.4.. :) Update:: i remove h_process = self.open_process(pid), but i get the same error for the next instruction if kernel32.DebugActiveProcess(pid) , so the problem i think in the loop while,, but what it is ???

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• stoping doGet/dopost in java servlets ?

  - by bosso

  Hello everyone, I've been playing with Java Servlets and Ajax a bit, and I've got a situation on which I would really appreciate advice. Let's say I have HTML page with a start and stop buttons, and as a result of clicking start button, overridden doGet (or doPost) method on a servlet is invoked which computes something that takes a long time to complete. (e.g. a giant loop, or even Infinite loop, doesn't matter, I'm interested in concepts here). So, I'm asking you: 1.What would be my options to kill / shut down / halt / exit doGet method whan I hit stop button on a web page? Do I use threading here, or there is simpler way? I take it that using System exit is not a very good idea, right? ;) 2.So, let's say I implement code for stopping doGet method. What would happen If I hit start on one browser(e.g.IE), and while this long computation takes place open new tab or other browser(e.g.Firefox) and open same url and hit stop? Would that stop my original computation? Is there any easy way to avoid this? I know that questions are a bit off, as I'm just starting with server-side of things. :) Any suggestions would be greatly appreciated!

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• Looking for a communication framework for delphi

  - by Ryan

  I am looking for a communication framework for delphi, we know there are so many communication frameworks for other languages , wcf, ecf and so forth, but i have nerver found the one for delphi till now , anybody who knows about it can give me an ider? There are some requirements i need ,as follows: Building an application(server or client) without caring how to do communications with each other between two endpoints. Imagine that we use mailbox for exchanging messages,it seems that the communication is transparent. Supports communication protocol extending. We often need to exchange the messages between 2 devices, but the communication protocol is not a public or general one, so we need to extend the framework,to implement a communication protocol for receiving or sending a message completely. Supports asynchronous and synchronous communication Supports transmission protocol extending. The transmission protocol can implemented by winsocket, pipes, com, windows message, mailslot and so forth. In client application, we can write code snips like follows: var server: TDelphiCommunicationServer; session : ICommunicationSession; request, response: IMessage; begin session := server.CreateSession('IP', Port); request := TLoginRequest.Create; session.SynSendMessage(request); session.WaitForMessage(response, INFINITE); ....... end; In above code snips , TLoginRequest has implemented the message interface.

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• CreateProcess doesn't pass command line arguments

  - by mnh

  Hello I have the following code but it isn't working as expected, can't figure out what the problem is. Basically, I'm executing a process (a .NET process) and passing it command line arguments, it is executed successfully by CreateProcess() but CreateProcess() isn't passing the command line arguments What am I doing wrong here?? int main(int argc, char* argv[]) { PROCESS_INFORMATION ProcessInfo; //This is what we get as an [out] parameter STARTUPINFO StartupInfo; //This is an [in] parameter ZeroMemory(&StartupInfo, sizeof(StartupInfo)); StartupInfo.cb = sizeof StartupInfo ; //Only compulsory field LPTSTR cmdArgs = "[email protected]"; if(CreateProcess("D:\\email\\smtp.exe", cmdArgs, NULL,NULL,FALSE,0,NULL, NULL,&StartupInfo,&ProcessInfo)) { WaitForSingleObject(ProcessInfo.hProcess,INFINITE); CloseHandle(ProcessInfo.hThread); CloseHandle(ProcessInfo.hProcess); printf("Yohoo!"); } else { printf("The process could not be started..."); } return 0; } EDIT: Hey one more thing, if I pass my cmdArgs like this: // a space as the first character LPTSTR cmdArgs = " [email protected]"; Then I get the error, then CreateProcess returns TRUE but my target process isn't executed. Object reference not set to an instance of an object

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• UpdatePanel doesn't load correctly on second try

  - by Ed Woodcock

  Ok, I've got two UpdatePanels on a (relatively simple) CRUD-management page, and I'm having some issues with them. The first updatepanel fails the second time it's updated (infinite loading popout, page doesn't change, request comes back properly but apparently isn't used). The second updatepanel fails if the first updatepanel has updated first, or if a certain internal trigger is pressed twice. Interestingly, the first updatepanel can be called multiple times with no problems if the first has yet to be called. layout example: <updatepanel> <table> <trigger> </table> </updatepanel> <lightbox> <updatepanel> <multiple triggers> </updatepanel> </lightbox> The use of the second updatepanel is required for the lightbox to function correctly (so it can't just be one big one). The first updatepanel exhibits this behaviour regardless of whether the second is present on the page or not. Has anyone ever experienced similar problems/have any ideas?

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• Looping Redirect with PyFacebook and Google App Engine

  - by Nick Gotch

  I have a Python Facebook project hosted on Google App Engine and use the following code to handle initialization of the Facebook API using PyFacebook. # Facebook Initialization def initialize_facebook(f): # Redirection handler def redirect(self, url): logger.info('Redirecting the user to: ' + url) self.response.headers.add_header("Cache-Control", "max-age=0") self.response.headers.add_header("Pragma", "no-cache") self.response.out.write('<html><head><script>parent.location.replace(\'' + url + '\');</script></head></html>') return 'Moved temporarily' auth_token = request.params.get('auth_token', None) fbapi = Facebook(settings['FACEBOOK_API_KEY'], settings['FACEBOOK_SECRET_KEY'], auth_token=auth_token) if not fbapi: logger.error('Facebook failed to initialize') if fbapi.check_session(request) or auth_token: pass else: logger.info('User not logged into Facebook') return lambda a: redirect(a, fbapi.get_login_url()) if fbapi.added: pass else: logger.info('User does not have ' + settings['FACEBOOK_APP_NAME'] + ' added') return lambda a: redirect(a, fbapi.get_add_url()) # Return the validated API logger.info('Facebook successfully initialized') return lambda a: f(a, fbapi=fbapi) I'm trying to set it up so that I can drop this decorator on any page handler method and verify that the user has everything set up correctly. The issue is that when the redirect handler gets called, it starts an infinite loop of redirection. I tried using an HTTP 302 redirection in place of the JavaScript but that kept failing too. Does anyone know what I can do to fix this? I saw this similar question but there are no answers.

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• Threading best practice when using SFTP in C#

  - by Christian

  Ok, this is more one of these "conceptual questions", but I hope I got some pointers in the right direction. First the desired scenario: I want to query an SFTP server for directory and file lists I want to upload or download files simulaneously Both things are pretty easy using a SFTP class provided by Tamir.SharpSsh, but if I only use one thread, it is kind of slow. Especially the recursion into subdirs gets very "UI blocking", because we are talking about 10.000 of directories. My basic approach is simple, create some kind of "pool" where I keep 10 open SFTP connections. Then query the first worker for a list of dirs. If this list was obtained, send the next free workers (e.g. 1-10, first one is also free again) to get the subdirectory details. As soon as there is a worker free, send him for the subsubdirs. And so on... I know the ThreadPool, simple Threads and did some Tests. What confuses me a little bit is the following: I basically need... A list of threads I create, say 10 Connect all threads to the server If a connection drops, create a new thread / sftp client If there is work to do, take the first free thread and handle the work I am currently not sure about the implementation details, especially the "work to do" and the "maintain list of threads" parts. Is it a good idea to: Enclose the work in an object, containing a job description (path) and a callback Send the threads into an infinite loop with 100ms wait to wait for work If SFTP is dead, either revive it, or kill the whole thread and create a new one How to encapsulate this, do I write my own "10ThreadsManager" or are there some out Ok, so far... Btw, I could also use PRISM events and commands, but I think the problem is unrelated. Perhaps the EventModel to signal a done processing of a "work package"... Thanks for any ideas, critic.. Chris

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• Objective C / iPhone comparing 2 CLLocations /GPS coordinates

  - by user289503

  have an app that finds your GPS location successfully, but I need to be able to compare that GPS with a list of GPS locations, if both are the same , then you get a bonus. I thought I had it working, but it seems not. I have 'newLocation' as the location where you are, I think the problem is that I need to be able to seperate the long and lat data of newLocation. So far ive tried this: Code: NSString *latitudeVar = [[NSString alloc] initWithFormat:@"%g°", newLocation.coordinate.latitude]; NSString *longitudeVar = [[NSString alloc] initWithFormat:@"%g°", newLocation.coordinate.longitude]; An example of the list of GPS locations: Code: location:(CLLocation*)newLocation; CLLocationCoordinate2D bonusOne; bonusOne.latitude = 37.331689; bonusOne.longitude = -122.030731; and then Code: if (latitudeVar == bonusOne.latitude && longitudeVar == bonusOne.longitude) { UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"infinite loop firday" message:@"infloop" delegate:nil cancelButtonTitle:@"Stinky" otherButtonTitles:nil ]; [alert show]; [alert release]; this comes up with an error 'invalid operands to binary == have strut NSstring and CLlocationDegrees' Any thoughts?

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• Attached event triggering if event is same as current event

  - by Psytronic

  I have a button which start/stops a timer. When I click it, I remove the current event handler, and attach the opposite one. Ie, click "Stop", and the "Start" function is attached for the next click. However in IE (7), not sure about 8. The newly attached event is also triggering after the original function is finished: Lifeline in IE7: Button pushed -- "Stop" function begins -- "Stop" function removed -- "Start" function attached -- "Stop" function finishes -- "Start" function is called. I know it's to do with the attaching event bit, because If I remove it, the Start event doesn't fire. This seems a bit odd, as I have the same situation in the "Start" function, ie, "Start" removed, "Stop" called. But this doesn't seem to cause an infinite loop, thankfully. if(btn.attachEvent){ btn.detachEvent("onclick", stop); btn.attachEvent("onclick", start); }else if(btn.addEventListener){ btn.removeEventListener("click", stop, true); btn.addEventListener("click", start , true); } It all works fine in FF and Chrome. I have switched the order of attach/detach, just to see if it makes a difference, but it doesn't. Addendum Sorry, and no answers involving jQuery, Protoype et al. Its not something I want to integrate for this project.

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• How to resize a Flot graph when its containing div changes size

  - by Will Gorman

  I'm using the Flot graphing library jQuery plugin and I haven't found a good way to handle resizing the graph when it's containing <div> changes size (for example, due to window resizing). When handling the onresize event, I've made sure that the width and height of the containing <div>are updated to the correct size and then tried calling both setupGrid and draw on the plot object but with no effect. I've had some success with the approach of just removing and readding the containing <div> and replotting the graph in it. However, this seems to be prone to getting stuck in infinite resize event loops if I have to add other <div> elements to the document at the same time (like for tooltips for the graph) as I'm guessing those can trigger resize events as well? Is there a good way to handle it that I'm missing? (I'm also using ExplorerCanvas for IE in order to be able to use Flot, if that might have anything to do with it. I haven't really tried in any other browsers yet)

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• Bitwise Interval Arithmetic

  - by KennyTM

  I've recently read an interesting thread on the D newsgroup, which basically asks, Given two signed integers a ∈ [amin, amax], b ∈ [bmin, bmax], what is the tightest interval of a | b? I'm think if interval arithmetics can be applied on general bitwise operators (assuming infinite bits). The bitwise-NOT and shifts are trivial since they just corresponds to -1 − x and 2n x. But bitwise-AND/OR are a lot trickier, due to the mix of bitwise and arithmetic properties. Is there a polynomial-time algorithm to compute the intervals of bitwise-AND/OR? Note: Assume all bitwise operations run in linear time (of number of bits), and test/set a bit is constant time. The brute-force algorithm runs in exponential time. Because ~(a | b) = ~a & ~b and a ^ b = (a | b) & ~(a & b), solving the bitwise-AND and -NOT problem implies bitwise-OR and -XOR are done. Although the content of that thread suggests min{a | b} = max(amin, bmin), it is not the tightest bound. Just consider [2, 3] | [8, 9] = [10, 11].)

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