Search Results

Search found 1358 results on 55 pages for 'concurrency violation'.

Page 42/55 | < Previous Page | 38 39 40 41 42 43 44 45 46 47 48 49  | Next Page >

• Using runtime checking of code contracts in Visual Studio 2010

  - by DigiMortal

  In my last posting about code contracts I introduced how to check input parameters of randomizer using static contracts checking. But you can also compile code contracts to your assemblies and use them also in runtime. In this posting I will show you simple example about runtime checking of code contracts. NB! If you want to play with code and try out things described here feel free to download example solution. if you are speaker and want to use this solution as a part of your sessions then feel free to do so, but don’t forget to refer me and this blog as source of this solution. And please let me know about your session. As a speaker I am very interested about it. :) To see how code contracts are checked at runtime we have to enable runtime checking from project properties. Make sure you have checked the box “Perform Runtime Contract Checking” and make sure you select “Full” from dropdown. These parts are in red box on the screenshot below. Visual Studio 2010 settings for code contracts. Runtime Checking is turned on and checks are made only in public surface. Click on image to see it at original size.  Save project settings. Then compile code and run it. As soon as code execution hits the call to GetRandomFromRangeContracted() exception is thrown. If you are not currently playing with solution referred above take a look at the following screenshot. Visual Studio 2010 runtime checking of code contracts. Exception of type ContractException is thrown when contract is violated. Click on image to see it at original size.  The exact type of exception is ContractException and it is defined in System.Diagnostics.Contracts.__ContractsRuntime namespace. In our example the message of exception is following: "Precondition failed: min < max  Min must be less than max" Besides the description we inserted for the case contract violation the message also contains violated contract type. In this case the type of contract is Precondition. Conclusion Using runtime checking of code contracts enables you to take code contracts with your code and have them checked every time when your methods are called. This way you can assure that all conditions are met to run method or exception is thrown and calling system has to handle the situation.

  Read the article

• Design pattern for an ASP.NET project using Entity Framework

  - by MPelletier

  I'm building a website in ASP.NET (Web Forms) on top of an engine with business rules (which basically resides in a separate DLL), connected to a database mapped with Entity Framework (in a 3rd, separate project). I designed the Engine first, which has an Entity Framework context, and then went on to work on the website, which presents various reports. I believe I made a terrible design mistake in that the website has its own context (which sounded normal at first). I present this mockup of the engine and a report page's code behind: Engine (in separate DLL): public Engine { DatabaseEntities _engineContext; public Engine() { // Connection string and procedure managed in DB layer _engineContext = DatabaseEntities.Connect(); } public ChangeSomeEntity(SomeEntity someEntity, int newValue) { //Suppose there's some validation too, non trivial stuff SomeEntity.Value = newValue; _engineContext.SaveChanges(); } } And report: public partial class MyReport : Page { Engine _engine; DatabaseEntities _webpageContext; public MyReport() { _engine = new Engine(); _databaseContext = DatabaseEntities.Connect(); } public void ChangeSomeEntityButton_Clicked(object sender, EventArgs e) { SomeEntity someEntity; //Wrong way: //Get the entity from the webpage context someEntity = _webpageContext.SomeEntities.Single(s => s.Id == SomeEntityId); //Send the entity from _webpageContext to the engine _engine.ChangeSomeEntity(someEntity, SomeEntityNewValue); // <- oops, conflict of context //Right(?) way: //Get the entity from the engine context someEntity = _engine.GetSomeEntity(SomeEntityId); //undefined above //Send the entity from the engine's context to the engine _engine.ChangeSomeEntity(someEntity, SomeEntityNewValue); // <- oops, conflict of context } } Because the webpage has its own context, giving the Engine an entity from a different context will cause an error. I happen to know not to do that, to only give the Engine entities from its own context. But this is a very error-prone design. I see the error of my ways now. I just don't know the right path. I'm considering: Creating the connection in the Engine and passing it off to the webpage. Always instantiate an Engine, make its context accessible from a property, sharing it. Possible problems: other conflicts? Slow? Concurrency issues if I want to expand to AJAX? Creating the connection from the webpage and passing it off to the Engine (I believe that's dependency injection?) Only talking through ID's. Creates redundancy, not always practical, sounds archaic. But at the same time, I already recuperate stuff from the page as ID's that I need to fetch anyways. What would be best compromise here for safety, ease-of-use and understanding, stability, and speed?

  Read the article

• JUDCon 2013 Trip Report

  - by reza_rahman

  JUDCon (JBoss Users and Developers Conference) 2013 was held in historic Boston on June 9-11 at the Hynes Convention Center. JUDCon is the largest get together for the JBoss community, has gone global in recent years but has it's roots in Boston. The JBoss folks graciously accepted a Java EE 7 talk from me and actually referenced my talk in their own sessions. I am proud to say this is my third time speaking at JUDCon/the Red Hat Summit over the years (this was the first time on behalf of Oracle). I had great company with many of the rock stars of the JBoss ecosystem speaking such as Lincoln Baxter, Jay Balunas, Gavin King, Mark Proctor, Andrew Lee Rubinger, Emmanuel Bernard and Pete Muir. Notably missing from JUDCon were Bill Burke, Burr Sutter, Aslak Knutsen and Dan Allen. Topics included Java EE, Forge, Arquillian, AeroGear, OpenShift, WildFly, Errai/GWT, NoSQL, Drools, jBPM, OpenJDK, Apache Camel and JBoss Tools/Eclipse. My session titled "JavaEE.Next(): Java EE 7, 8, and Beyond" went very well and it was a full house. This is our main talk covering the changes in JMS 2, the Java API for WebSocket (JSR 356), the Java API for JSON Processing (JSON-P), JAX-RS 2, JPA 2.1, JTA 1.2, JSF 2.2, Java Batch, Bean Validation 1.1, Java EE Concurrency and the rest of the APIs in Java EE 7. I also briefly talked about the possibilities for Java EE 8. The slides for the talk are here: JavaEE.Next(): Java EE 7, 8, and Beyond from reza_rahman Besides presenting my talk, it was great to catch up with the JBoss gang and attend a few interesting sessions. On Sunday night I went to one of my favorite hangouts in Boston - the exalted Middle East Club as Rolling Stone refers to it (other cool spots in an otherwise pretty boring town is "the Church"). As contradictory as it might sound to the uninitiated, the Middle East Club is possibly the best place in Boston to simultaneously get great Middle Eastern (primarily Lebanese) food and great underground metal. For folks with a bit more exposure, this is probably not contradictory at all given bands like Acrassicauda and documentaries like Heavy Metal in Baghdad. Luckily for me they were featuring a few local Thrash metal bands from the greater Boston area. It wasn't too bad considering it was primarily amateur twenty-something guys (although I'm not sure I'm a qualified critic any more since I all but stopped playing about at that age). It's great Boston has the Middle East as an incubator to keep the rock, metal, folk, jazz, blues and indie scene alive. I definitely enjoyed JUDCon/Boston and hope to be part of the conference next year again.

  Read the article

• Configure Calendar Server 7 to Use the davUniqueId Attribute

  - by dabrain

  Starting with Calendar Server 7 Update 3 (Patch 08) we introduce a new attribute davUniqueId in the davEntity objectclass, to use as the unique identifier.  The reason behind this is quite simple, the LDAP operational attribute nsUniqueId  has been chosen as the default value used for the unique identifier. It was discovered that this choice has a potential serious downside. The problem with using nsUniqueId is that if the LDAP entry for a user, group, or resource is deleted and recreated in LDAP, the new entry would receive a different nsUniqueId value from the Directory Server, causing a disconnect from the existing account in the calendar database. As a result, recreated users cannot access their existing calendars. How To Configure Calendar Server to Use the davUniqueId Attribute? Populate the davUniqueId to the ldap users. You can create a LDIF output file only or (-x option) directly run the ldapmodify from the populate-davuniqueid shell script. # ./populate-davuniqueid -h localhost -p 389 -D "cn=Directory Manager" -w <passwd> -b "o=red" -O -o /tmp/out.ldif The ldapmodify might failed like below, in that case the LDAP entry already have the 'daventity' objectclass, in those cases run populate-davuniqueid script without the -O option. # ldapmodify -x -h localhost -p 389 -D "cn=Directory Manager" -w <passwd> -c -f /tmp/out.ldif modifying entry "uid=mparis,ou=People,o=vmdomain.tld,o=red" ldapmodify: Type or value exists (20) In this case the user 'mparis' already have the objectclass 'daventity', ldapmodify do not take care of this DN and just take the next DN (if you start ldapmodify with -c option otherwise it stop's completely) dn: uid=mparis,ou=People,o=vmdomain.tld,o=red changetype: modify add: objectclass objectclass: daventity - add: davuniqueid davuniqueid: 01a2c501-af0411e1-809de373-18ff5c8d Even run populate-davuniqueid without -O option or changing the outputfile to dn: uid=mparis,ou=People,o=vmdomain.tld,o=red changetype: modify add: davuniqueid davuniqueid: 01a2c501-af0411e1-809de373-18ff5c8d The ldapmodify works fine now. The only issue I see here is you need verify which user might need the 'daventity' objectclass as well. On the other hand start without the objectclass and only add the objectclass for the users where you get 'Objectclass violation' report. That's indicate the objectclass is missing. # ldapmodify -x -h localhost -p 389 -D "cn=Directory Manager" -w <passwd> -c -f /tmp/out.ldif modifying entry "uid=mparis,ou=People,o=vmdomain.tld,o=red" Now it is time to change the configuration to use the davuniquid attribute # ./davadmin config modify -o davcore.uriinfo.permanentuniqueid -v davuniqueid It is also needed to modfiy the search filter to use davuniqueid instead of nsuniqueid # ./davadmin config modify -o davcore.uriinfo.subjectattributes -v "cn davstore icsstatus mail mailalternateaddress davUniqueId  owner preferredlanguageuid objectclass ismemberof uniquemember memberurl mgrprfc822mailmember" Afterward IWC Calendar works fine and my test user able to access all his old events.

  Read the article

• C++ Accelerated Massive Parallelism

  - by Daniel Moth

  At AMD's Fusion conference Herb Sutter announced in his keynote session a technology that our team has been working on that we call C++ Accelerated Massive Parallelism (C++ AMP) and during the keynote I showed a brief demo of an app built with our technology. After the keynote, I go deeper into the technology in my breakout session. If you read both those abstracts, you'll get some information about what C++ AMP is, without being too explicit since we published the abstracts before the technology was announced. You can find the official online announcement at Soma's blog post. Here, I just wanted to capture the key points about C++ AMP that can serve as an introduction and an FAQ. So, in no particular order… C++ AMP lowers the barrier to entry for heterogeneous hardware programmability and brings performance to the mainstream, without sacrificing developer productivity or solution portability. is designed not only to help you address today's massively parallel hardware (i.e. GPUs and APUs), but it also future proofs your code investments with a forward looking design. is part of Visual C++. You don't need to use a different compiler or learn different syntax. is modern C++. Not C or some other derivative. is integrated and supported fully in Visual Studio vNext. Editing, building, debugging, profiling and all the other goodness of Visual Studio work well with C++ AMP. provides an STL-like library as part of the existing concurrency namespace and delivered in the new amp.h header file. makes it extremely easy to work with large multi-dimensional data on heterogeneous hardware; in a manner that exposes parallelization. introduces only one core C++ language extension. builds on DirectX (and DirectCompute in particular) which offers a great hardware abstraction layer that is ubiquitous and reliable. The architecture is such, that this point can be thought of as an implementation detail that does not surface to the API layer. Stay tuned on my blog for more over the coming months where I will switch from just talking about C++ AMP to showing you how to use the API with code examples… Comments about this post welcome at the original blog.

  Read the article

• How do we keep dependent data structures up to date?

  - by Geo

  Suppose you have a parse tree, an abstract syntax tree, and a control flow graph, each one logically derived from the one before. In principle it is easy to construct each graph given the parse tree, but how can we manage the complexity of updating the graphs when the parse tree is modified? We know exactly how the tree has been modified, but how can the change be propagated to the other trees in a way that doesn't become difficult to manage? Naturally the dependent graph can be updated by simply reconstructing it from scratch every time the first graph changes, but then there would be no way of knowing the details of the changes in the dependent graph. I currently have four ways to attempt to solve this problem, but each one has difficulties. Nodes of the dependent tree each observe the relevant nodes of the original tree, updating themselves and the observer lists of original tree nodes as necessary. The conceptual complexity of this can become daunting. Each node of the original tree has a list of the dependent tree nodes that specifically depend upon it, and when the node changes it sets a flag on the dependent nodes to mark them as dirty, including the parents of the dependent nodes all the way down to the root. After each change we run an algorithm that is much like the algorithm for constructing the dependent graph from scratch, but it skips over any clean node and reconstructs each dirty node, keeping track of whether the reconstructed node is actually different from the dirty node. This can also get tricky. We can represent the logical connection between the original graph and the dependent graph as a data structure, like a list of constraints, perhaps designed using a declarative language. When the original graph changes we need only scan the list to discover which constraints are violated and how the dependent tree needs to change to correct the violation, all encoded as data. We can reconstruct the dependent graph from scratch as though there were no existing dependent graph, and then compare the existing graph and the new graph to discover how it has changed. I'm sure this is the easiest way because I know there are algorithms available for detecting differences, but they are all quite computationally expensive and in principle it seems unnecessary so I'm deliberately avoiding this option. What is the right way to deal with these sorts of problems? Surely there must be a design pattern that makes this whole thing almost easy. It would be nice to have a good solution for every problem of this general description. Does this class of problem have a name?

  Read the article

• Best Creational Pattern for loggers in a multi-threaded system?

  - by Dipan Mehta

  This is a follow up question on my past questions : Concurrency pattern of logger in multithreaded application As suggested by others, I am putting this question separately. As the learning from the last question. In a multi-threaded environment, the logger should be made thread safe and probably asynchronous (where in messages are queued while a background thread does writing releasing the requesting object thread). The logger could be signleton or it can be a per-group logger which is a generalization of the above. Now, the question that arise is how does logger should be assigned to the object? There are two options I can think of: 1. Object requesting for the logger: Should each of the object call some global API such as get_logger()? Such an API returns "the" singleton or the group logger. However, I feel this involves assumption about the Application environment to implement the logger -which I think is some kind of coupling. If the same object needs to be used by other application - this new application also need to implement such a method. 2. Assign logger through some known API The other alternative approach is to create a kind of virtual class which is implemented by application based on App's own structure and assign the object sometime in the constructor. This is more generalized method. Unfortunately, when there are so many objects - and rather a tree of objects passing on the logger objects to each level is quite messy. My question is there a better way to do this? If you need to pick any one of the above, which approach is would you pick and why? Other questions remain open about how to configure them: How do objects' names or ID are assigned so that will be used for printing on the log messages (as the module names) How do these objects find the appropriate properties (such as log levels, and other such parameters) In the first approach, the central API needs to deal with all this varieties. In the second approach - there needs to be additional work. Hence, I want to understand from the real experience of people, as to how to write logger effectively in such an environment.

  Read the article

• Is there a pedagogical game engine?

  - by K.G.

  I'm looking for a book, website, or other resource that gives modern 3D game engines the same treatment as Operating Systems: Design and Implementation gave operating systems. I have read Jason Gregory's Game Engine Architecture, which I enjoyed. However, by intent the author treated components of the architecture as atomic units, whereas what I'm interested in is the plumbing between those units that makes a coherent whole out of ideally loosely coupled parts. In books such as these, one usually reads that "that's academic," but that's the point! I have also read Julian Gold's Object-oriented Game Development, which likewise was good, but I feel is beginning to show its age. Since even mobile platforms these days are multicore and have fast video memory, those kinds of things (concurrency, display item buffering) would ideally be covered. There are other resources, such as the Doom 3 source code, which is highly instructive for its being a shipped product. The problem with those is as follows: float Q_rsqrt( float number ) { long i; float x2, y; const float threehalfs = 1.5F; x2 = number * 0.5F; y = number; i = * ( long * ) &y; // evil floating point bit level hacking i = 0x5f3759df - ( i >> 1 ); // what the f***? y = * ( float * ) &i; y = y * ( threehalfs - ( x2 * y * y ) ); // 1st iteration // y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed return y; } To wit, while brilliant, this kind of source requires more enlightenment than I can usually muster upon first read. In summary, here's my white whale: For an adult reader with experience in programming. I wish I could save all the trees killed by every. Single. Game Programming book ever devoting the first two chapters to "Now just what is a variable anyway?" In C or C++, very preferably C++. Languages that are more concise are fantastic for teaching, except for when what you want to learn is how to cope with a verbose language. There is also the benefit of the guardrails that C++ doesn't provide, such as garbage collection. Platform agnostic. I'm sincerely afraid that this book is out there and it's Visual C++/DirectX oriented. I'm a Linux guy, and I'd do what it takes, but I would very much like to be able to use OpenGL. Thanks for everything! Before anyone gets on my case about it, Fast inverse square root was from Quake III Arena, not Doom 3!

  Read the article

• How granular should a command be in a CQ[R]S model?

  - by Aaronaught

  I'm considering a project to migrate part of our WCF-based SOA over to a service bus model (probably nServiceBus) and using some basic pub-sub to achieve Command-Query Separation. I'm not new to SOA, or even to service bus models, but I confess that until recently my concept of "separation" was limited to run-of-the-mill database mirroring and replication. Still, I'm attracted to the idea because it seems to provide all the benefits of an eventually-consistent system while sidestepping many of the obvious drawbacks (most notably the lack of proper transactional support). I've read a lot on the subject from Udi Dahan who is basically the guru on ESB architectures (at least in the Microsoft world), but one thing he says really puzzles me: As we get larger entities with more fields on them, we also get more actors working with those same entities, and the higher the likelihood that something will touch some attribute of them at any given time, increasing the number of concurrency conflicts. [...] A core element of CQRS is rethinking the design of the user interface to enable us to capture our users’ intent such that making a customer preferred is a different unit of work for the user than indicating that the customer has moved or that they’ve gotten married. Using an Excel-like UI for data changes doesn’t capture intent, as we saw above. -- Udi Dahan, Clarified CQRS From the perspective described in the quotation, it's hard to argue with that logic. But it seems to go against the grain with respect to SOAs. An SOA (and really services in general) are supposed to deal with coarse-grained messages so as to minimize network chatter - among many other benefits. I realize that network chatter is less of an issue when you've got highly-distributed systems with good message queuing and none of the baggage of RPC, but it doesn't seem wise to dismiss the issue entirely. Udi almost seems to be saying that every attribute change (i.e. field update) ought to be its own command, which is hard to imagine in the context of one user potentially updating hundreds or thousands of combined entities and attributes as it often is with a traditional web service. One batch update in SQL Server may take a fraction of a second given a good highly-parameterized query, table-valued parameter or bulk insert to a staging table; processing all of these updates one at a time is slow, slow, slow, and OLTP database hardware is the most expensive of all to scale up/out. Is there some way to reconcile these competing concerns? Am I thinking about it the wrong way? Does this problem have a well-known solution in the CQS/ESB world? If not, then how does one decide what the "right level" of granularity in a Command should be? Is there some "standard" one can use as a starting point - sort of like 3NF in databases - and only deviate when careful profiling suggests a potentially significant performance benefit? Or is this possibly one of those things that, despite several strong opinions being expressed by various experts, is really just a matter of opinion?

  Read the article

• "Hello World" in C++ AMP

  - by Daniel Moth

  Some say that the equivalent of "hello world" code in the data parallel world is matrix multiplication :) Below is the before C++ AMP and after C++ AMP code. For more on what it all means, watch the recording of my C++ AMP introduction (the example below is part of the session). void MatrixMultiply(vector<float>& vC, const vector<float>& vA, const vector<float>& vB, int M, int N, int W ) { for (int y = 0; y < M; y++) { for (int x = 0; x < N; x++) { float sum = 0; for(int i = 0; i < W; i++) { sum += vA[y * W + i] * vB[i * N + x]; } vC[y * N + x] = sum; } } } Change the function to use C++ AMP and hence offload the computation to the GPU, and now the calling code (which I am not showing) needs no changes and the overall operation gives you really nice speed up for large datasets…  #include <amp.h> using namespace concurrency; void MatrixMultiply(vector<float>& vC, const vector<float>& vA, const vector<float>& vB, int M, int N, int W ) { array_view<const float,2> a(M, W, vA); array_view<const float,2> b(W, N, vB); array_view<writeonly<float>,2> c(M, N, vC); parallel_for_each( c.grid, [=](index<2> idx) mutable restrict(direct3d) { float sum = 0; for(int i = 0; i < a.x; i++) { sum += a(idx.y, i) * b(i, idx.x); } c[idx] = sum; } ); } Again, you can understand the elements above, by using my C++ AMP presentation slides and recording… Stay tuned for more… Comments about this post welcome at the original blog.

  Read the article

• Using Query Classes With NHibernate

  - by Liam McLennan

  Even when using an ORM, such as NHibernate, the developer still has to decide how to perform queries. The simplest strategy is to get access to an ISession and directly perform a query whenever you need data. The problem is that doing so spreads query logic throughout the entire application – a clear violation of the Single Responsibility Principle. A more advanced strategy is to use Eric Evan’s Repository pattern, thus isolating all query logic within the repository classes. I prefer to use Query Classes. Every query needed by the application is represented by a query class, aka a specification. To perform a query I: Instantiate a new instance of the required query class, providing any data that it needs Pass the instantiated query class to an extension method on NHibernate’s ISession type. To query my database for all people over the age of sixteen looks like this: [Test] public void QueryBySpecification() { var canDriveSpecification = new PeopleOverAgeSpecification(16); var allPeopleOfDrivingAge = session.QueryBySpecification(canDriveSpecification); } To be able to query for people over a certain age I had to create a suitable query class: public class PeopleOverAgeSpecification : Specification<Person> { private readonly int age; public PeopleOverAgeSpecification(int age) { this.age = age; } public override IQueryable<Person> Reduce(IQueryable<Person> collection) { return collection.Where(person => person.Age > age); } public override IQueryable<Person> Sort(IQueryable<Person> collection) { return collection.OrderBy(person => person.Name); } } Finally, the extension method to add QueryBySpecification to ISession: public static class SessionExtensions { public static IEnumerable<T> QueryBySpecification<T>(this ISession session, Specification<T> specification) { return specification.Fetch( specification.Sort( specification.Reduce(session.Query<T>()) ) ); } } The inspiration for this style of data access came from Ayende’s post Do You Need a Framework?. I am sick of working through multiple layers of abstraction that don’t do anything. Have you ever seen code that required a service layer to call a method on a repository, that delegated to a common repository base class that wrapped and ORMs unit of work? I can achieve the same thing with NHibernate’s ISession and a single extension method. If you’re interested you can get the full Query Classes example source from Github.

  Read the article

• Java @Contented annotation to help reduce false sharing

  - by Dave

  See this posting by Aleksey Shipilev for details -- @Contended is something we've wanted for a long time. The JVM provides automatic layout and placement of fields. Usually it'll (a) sort fields by descending size to improve footprint, and (b) pack reference fields so the garbage collector can process a contiguous run of reference fields when tracing. @Contended gives the program a way to provide more explicit guidance with respect to concurrency and false sharing. Using this facility we can sequester hot frequently written shared fields away from other mostly read-only or cold fields. The simple rule is that read-sharing is cheap, and write-sharing is very expensive. We can also pack fields together that tend to be written together by the same thread at about the same time. More generally, we're trying to influence relative field placement to minimize coherency misses. Fields that are accessed closely together in time should be placed proximally in space to promote cache locality. That is, temporal locality should condition spatial locality. Fields accessed together in time should be nearby in space. That having been said, we have to be careful to avoid false sharing and excessive invalidation from coherence traffic. As such, we try to cluster or otherwise sequester fields that tend to written at approximately the same time by the same thread onto the same cache line. Note that there's a tension at play: if we try too hard to minimize single-threaded capacity misses then we can end up with excessive coherency misses running in a parallel environment. Theres no single optimal layout for both single-thread and multithreaded environments. And the ideal layout problem itself is NP-hard. Ideally, a JVM would employ hardware monitoring facilities to detect sharing behavior and change the layout on the fly. That's a bit difficult as we don't yet have the right plumbing to provide efficient and expedient information to the JVM. Hint: we need to disintermediate the OS and hypervisor. Another challenge is that raw field offsets are used in the unsafe facility, so we'd need to address that issue, possibly with an extra level of indirection. Finally, I'd like to be able to pack final fields together as well, as those are known to be read-only.

  Read the article

• Criteria for a programming language to be considered "mature"

  - by Giorgio

  I was recently reading an answer to this question, and I was struck by the statement "The language is mature". So I was wondering what we actually mean when we say that "A programming language is mature"? Normally, a programming language is initially developed out of a need, e.g. Try out / implement a new programming paradigm or a new combination of features that cannot be found in existing languages. Try to solve a problem or overcome a limitation of an existing language. Create a language for teaching programming. Create a language that solves a particular class of problems (e.g. concurrency). Create a language and an API for a special application field, e.g. the web (in this case the language might reuse a well-known paradigm, but the whole API must be new). Create a language to push your competitor out of the market (in this case the creator might want the new language to be very similar to an existing one, in order to attract developers to the new programming language and platform). Regardless of what the original motivation and scenario in which a language has been created, eventually some languages are considered mature. In my intuition, this means that the language has achieved (at least one of) its goals, e.g. "We can now use language X as a reliable tool for writing web applications." This is however a bit vague, so I wanted to ask what you consider the most important criteria (if any) that are applied when saying that a language is mature. IMPORTANT NOTE This question is (on purpose) language-agnostic because I am only interested in general criteria. Please write only language-agnostic answers and comments! I am not asking whether any specific "language X is mature" or "which programming languages can be considered mature", or whether "language X is more mature than language Y": please avoid posting any opinions or reference about any specific languages because these are out of the scope of this question. EDIT To make the question more precise, by criteria I mean such things as "tool support", "adoption by the industry", "stability", "rich API", "large user community", "successful application record", "standardization", "clean and uniform semantics", and so on.

  Read the article

• Programming tourism

  - by Andrew_B

  I'm going on vacation to Paris, France for 10 days. Actually, it's my girlfriend's wish to go there but I'm not very interested in visiting, sightseeing, etc. Recently, I came up with an idea of trying to do something like programming tourism. :) I'd like to do something related to programming in a startup-like company. I do not want a salary or any kind of compensation. I want to overview process, social aspects, environment and "what it feels like" to development software in another country. I'm from Russia. I've been a software developer since 2003. I prefer C#4 but I'm ready to use anything Turing-complete. I have some MS certifications and am familiar with all .NETs since 1.1. Currently I'm finishing PhD in CS. I'm interested in multidimensional indexing and I can turn any piece of data and code to OLAP system. :) But it'd take too much time. What can I do? I have no more than one week. I want a totally complete project in a short amount of time. Implement some features in well-tested project Do a code review Debug memory, performance and concurrency issues Do unit testing So, about the questions: Is it legal? I'm ready to sign NDA if it's necessary. I'll have tourist visa. Is it possible? I'm really sure that bureaucratic companies with lots of HRs and PMs will not allow such experiments. But small companies can afford it. I'm ready to guarantee support on my code after leaving home :) P.S. I still havn't started learning French :) I hope it will not take too much time :) P.P.S. Yes, it's girlfriend-approved. What's in it for me? It's fun. It's fun to see new systems and people who created them. It's fun to complete meaningful things. Quickly. What's in it for them? Feature, debug, review or test. If my short-term colleagues will like this style of working I can invite them to make same trip into my company :) I think in Russia it's even more exciting :)

  Read the article

• Kodak Scanner Software Issue 0xc0000005

  - by Andrew

  I am trying to be able to use a program called Kodak Smart Touch, but just today I have experienced an error preventing it from opening. The scanner is a business class scanner, an i2900. It comes with a small program called Kodak Smart Touch. This program allows you to select and customize a number of presets on the front panel and automatically create/save scanned files, etc. I was running a backup with Aomei Backupper at the time, and I wanted to scan a file. I tried to scan as normal, but right at the end the program quit with an error. Now, whenever I try to start Smart Touch, even not running the backup and with Aomei uninstalled, the following error pops up: Title of message: KSSCFG (version 1.7.15.121102) has stopped working. Body: See (path name) for more information. When I go to the path in the error message, there are two files, ERRORLOG.txt and KSSCFG.dmp. The error log says, "KSSCFG (version 1.7.15.322.121102) case an Access Violation(0xc0000005). Error occur at 2014/06/11 21:37:54 Operation System: Windows 7 64bits (6.1.7601) processor(s) type AMD x86 or x64" The dump file can be downloaded here: http://l.bitcasa.com/yzbtv1VV Opening it with a hex editor yields very little of use, but I do have an internal commandline utility that may help: http://l.bitcasa.com/cTXvAsst I've already uninstalled and reinstalled all the kodak software several times to no avail. What is really odd is that the TWAIN and ISIS drivers work fine through another scanning program. I am at my wit's end, and I have no idea what to do next. Thanks.

  Read the article

• Occasional disk I/O errors in SQLite

  - by Alix Axel

  I have a very simple website running PHP and SQLite 3.7.9 (with PDO). After establishing the SQLite connection I immediately execute the following queries: PRAGMA busy_timeout=0; PRAGMA cache_size=8192; PRAGMA foreign_keys=ON; PRAGMA journal_size_limit=67110000; PRAGMA legacy_file_format=OFF; PRAGMA page_size=4096; PRAGMA recursive_triggers=ON; PRAGMA secure_delete=ON; PRAGMA synchronous=NORMAL; PRAGMA temp_store=MEMORY; PRAGMA journal_mode=WAL; PRAGMA wal_autocheckpoint=4096; This website only has one writer and a few occasional readers, so I don't expect any concurrency problems (and I'm even using WAL). Every couple of days, I've seen this error being reported by PHP: Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General error: 10 disk I/O error' in ... Stack trace: #0 ...: PDO-exec('PRAGMA cache_si...') There are several things that make this error very weird to me: it's not a transient problem - no matter how many times I refresh the page, it won't go away the database file is not corrupted - the sqlite3 executable can open the database without problems If the following pragmas are commented out, PHP stops throwing the disk I/O exception: PRAGMA cache_size=8192; PRAGMA synchronous=NORMAL; PRAGMA journal_mode=WAL; Then, after successfully reconnecting to the database, I'm able to reintroduce these pragmas and the code with run smoothly for days - until eventually, the same error will occur without any apparent reason. I wasn't able to reproduce this error so far, so I'm clueless about the origin of it. I'm really curious what may be causing this problem... Any ideas? Environment: Ubuntu Server 12.04 LTS PHP 5.4.15 SQLite 3.7.9 Database size: ? 10MiB Transaction (write) size: ? 1KiB EDIT: Might these symptoms have something to do with busy_timeout?

  Read the article

• Could not continue scan with NOLOCK due to data movement during installation

  - by dbdev1

  I am running Windows Server 2008 Standard Edition R2 x64 and I installed SQL Server 2008 Developer Edition. All of the preliminary checks run fine (Apart from a warning about Windows Firewall and opening ports which is unrelated to this and shouldn't be an issue - I can open those ports). Half way through the actual installation, I get a popup with this error: Could not continue scan with NOLOCK due to data movement. The installation still runs to completion when I press ok. However, at the end, it states that the following services "failed": database engine services sql server replication full-text search reporting services How do I know if this actually means that anything from my installation (which is on a clean Windows Server setup - nothing else on there, no previous SQL Servers, no upgrades, etc) is missing? I know from my programming experience that locks are for concurrency control and the Microsoft help on this issue points to changing my query's lock/transactions in a certain way to fix the issue. But I am not touching any queries? Also, now that I have installed the app, when I login, I keep getting this message: TITLE: Connect to Server ------------------------------ Cannot connect to MSSQLSERVER. ------------------------------ ADDITIONAL INFORMATION: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 67) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&EvtSrc=MSSQLServer&EvtID=67&LinkId=20476 ------------------------------ BUTTONS: OK ------------------------------ I went into the Configuration Manager and enabled named pipes and restarted the service (this is something I have done before as this message is common and not serious). I have disabled Windows Firewall temporarily. I have checked the instance name against the error logs. Please advise on both of these errors. I think these two errors are related. Thanks

  Read the article

• Apachebench on node.js server returning "apr_poll: The timeout specified has expired (70007)" after ~30 requests

  - by Scott

  I just started working with node.js and doing some experimental load testing with ab is returning an error at around 30 requests or so. I've found other pages showing a lot better concurrency numbers than I am such as: http://zgadzaj.com/benchmarking-nodejs-basic-performance-tests-against-apache-php Are there some critical server configuration settings that need done to achieve those numbers? I've watched memory on top and I still see a decent amount of free memory while running ab, watched mongostat as well and not seeing anything that looks suspicious. The command I'm running, and the error is: ab -k -n 100 -c 10 postrockandbeyond.com/ This is ApacheBench, Version 2.0.41-dev <$Revision: 1.121.2.12 $> apache-2.0 Copyright (c) 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Copyright (c) 2006 The Apache Software Foundation, http://www.apache.org/ Benchmarking postrockandbeyond.com (be patient)...apr_poll: The timeout specified has expired (70007) Total of 32 requests completed Does anyone have any suggestions on things I should look in to that may be causing this? I'm running it on osx lion, but have also run the same command on the server with the same results. EDIT: I eventually solved this issue. I was using a TTAPI, which was connecting to turntable.fm through websockets. On the homepage, I was connecting on every request. So what was happening was that after a certain number of connections, everything would fall apart. If you're running into the same issue, check out whether you are hitting external services each request.

  Read the article

• PostgreSQL lots of writes

  - by strife911

  Hi, I am using postgreSQL for a scientific application (unsupervised clustering). The python program is multi-threaded so that each thread manages its own postmaster process (one per core). Hence, their is a lot of concurrency. Each thread-process loop infinitely though two SQL queries. The first is for reading, the second is for writing. The read operation considers 500 time the amount of rows the write operation considers. Here is the output of dstat: ----total-cpu-usage---- ------memory-usage----- -dsk/total- --paging-- --io/total- usr sys idl wai hiq siq| used buff cach free| read writ| in out | read writ 4 0 32 64 0 0|3599M 63M 57G 1893M|1524k 16M| 0 0 | 98 2046 1 0 35 64 0 0|3599M 63M 57G 1892M|1204k 17M| 0 0 | 68 2062 2 0 32 66 0 0|3599M 63M 57G 1890M|1132k 17M| 0 0 | 62 2033 2 1 32 65 0 0|3599M 63M 57G 1904M|1236k 18M| 0 0 | 80 1994 2 0 31 67 0 0|3599M 63M 57G 1903M|1312k 16M| 0 0 | 70 1900 2 0 37 60 0 0|3599M 63M 57G 1899M|1116k 15M| 0 0 | 71 1594 2 1 37 60 0 0|3599M 63M 57G 1898M| 448k 17M| 0 0 | 39 2001 2 0 25 72 0 0|3599M 63M 57G 1896M|1192k 17M| 0 0 | 78 1946 1 0 40 58 0 0|3599M 63M 57G 1895M| 432k 15M| 0 0 | 38 1937 I am pretty sure I could write more often than that for I have seen it write up to 110-140M on dstat. How can I optimize this process?

  Read the article

• Could not continue scan with NOLOCK due to data movement during installation

  - by dbdev1

  Hi, I am running Windows Server 2008 Standard Edition R2 x64 and I installed SQL Server 2008 Developer Edition. All of the preliminary checks run fine (Apart from a warning about Windows Firewall and opening ports which is unrelated to this and shouldn't be an issue - I can open those ports). Half way through the actual installation, I get a popup with this error: Could not continue scan with NOLOCK due to data movement. The installation still runs to completion when I press ok. However, at the end, it states that the following services "failed": database engine services sql server replication full-text search reporting services How do I know if this actually means that anything from my installation (which is on a clean Windows Server setup - nothing else on there, no previous SQL Servers, no upgrades, etc) is missing? I know from my programming experience that locks are for concurrency control and the Microsoft help on this issue points to changing my query's lock/transactions in a certain way to fix the issue. But I am not touching any queries? Also, now that I have installed the app, when I login, I keep getting this message: TITLE: Connect to Server Cannot connect to MSSQLSERVER. ADDITIONAL INFORMATION: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 67) For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&EvtSrc=MSSQLServer&EvtID=67&LinkId=20476 BUTTONS: OK I went into the Configuration Manager and enabled named pipes and restarted the service (this is something I have done before as this message is common and not serious). I have disabled Windows Firewall temporarily. I have checked the instance name against the error logs. Please advise on both of these errors. I think these two errors are related. Thanks

  Read the article

• How to collect the performance data of a server during an unreachable/down period using Nagios?

  - by gsc-frank

  Some time services and host stop responding due to a poor server performance. I mean, if for some reason (could be lot of concurrency services access, a expensive backup execution on the server or whatever that consume tons of server resources) a server performance is very degraded, that could lead that the server isn't capable to establish any "normal network communication" (without trigger whatever standards timeouts defined for such communication). Knowing host's performance data (cpu, memory, ...) in case of available during that period (host is not down and despite of its performance degradation still allow plugins collect performance data) could be very useful for sysadmin to try to determine what cause the problem, or at least, if the host performance was good and don't interfered at all in the host/service down. This problem could be solved using remote active (NRPE) or remote passive (NSCA) if such remote solutions could store (buffered) perf data to be send to central Nagios server when host performance or network outage allow it. I read the doc of both solutions and can't find any reference to such buffer mechanism neither what happened in case that NSCA can't reach Nagios server. Any idea of how solve this lack of info? so useful for forensic analysis. EDIT: My questions isn about which tools I can use to debug perf problems or gather perf data to analysis, but is about how collect (using Nagios) host perf data even during a network outage for its posterior analysis (kind of forensic analysis). The idea is integrate such data to Nagios graphers like pnp4nagios and NagiosGrapther. I know that I could install tools like Cacti in each of my host, and have a kind of performance data collection redundancy, but I really want avoid that and try to solve all perf analysis requirements with one tools: Nagios

  Read the article

• how do i write an init script for django-supervisor

  - by amateur

  pardon me as this is my first time attempting to write a init script for centos 5. I am using django + supervisor to manage my celery workers, scheduler. Now, this is my naive simple attempt /etc/init.d/supervisor #!/bin/sh # # /etc/rc.d/init.d/supervisord # # Supervisor is a client/server system that # allows its users to monitor and control a # number of processes on UNIX-like operating # systems. # # chkconfig: - 64 36 # description: Supervisor Server # processname: supervisord # Source init functions /home/foo/virtualenv/property_env/bin/python /home/foo/bar/manage.py supervisor --daemonize inside my supervisor.conf: [program:celerybeat] command=/home/property/virtualenv/property_env/bin/python manage.py celerybeat --loglevel=INFO --logfile=/home/property/property_buyer/logfiles/celerybeat.log [program:celeryd] command=/home/foo/virtualenv/property_env/bin/python manage.py celeryd --loglevel=DEBUG --logfile=/home/foo/bar/logfiles/celeryd.log --concurrency=1 -E [program:celerycam] command=/home/foo/virtualenv/property_env/bin/python manage.py celerycam I couldn't get it to work. 2013-08-06 00:21:03,108 INFO exited: celerybeat (exit status 2; not expected) 2013-08-06 00:21:06,114 INFO spawned: 'celeryd' with pid 11772 2013-08-06 00:21:06,116 INFO spawned: 'celerycam' with pid 11773 2013-08-06 00:21:06,119 INFO spawned: 'celerybeat' with pid 11774 2013-08-06 00:21:06,146 INFO exited: celerycam (exit status 2; not expected) 2013-08-06 00:21:06,147 INFO gave up: celerycam entered FATAL state, too many start retries too quickly 2013-08-06 00:21:06,147 INFO exited: celeryd (exit status 2; not expected) 2013-08-06 00:21:06,152 INFO gave up: celeryd entered FATAL state, too many start retries too quickly 2013-08-06 00:21:06,152 INFO exited: celerybeat (exit status 2; not expected) 2013-08-06 00:21:07,153 INFO gave up: celerybeat entered FATAL state, too many start retries too quickly I believe it is the init script, but please help me understand what is wrong.

  Read the article

• Samba PDC share slow with LDAP backend

  - by hmart

  The scenario I have a SUSE SLES 11.1 SP1 machine as Samba master PDC with LDAP backend. In one share there are Database files for a Client-Server application. I log XP and Windows 7 machines to the local domain (example.local), the login is a little slow but works. In the client computers have an executable which opens, reads and writes the database files from the server share. The Problem When running Samba with LDAP password backend the client application runs VERY SLOW with a maximum transfer rate of 2500 MBit per second. If disable LDAP the client app speed increases 20x, with transfer rate of 50Mbit/sec and running smoothly. I'm doing test with just two users and two machines, so concurrency, or LDAP size shouldn't be the problem here. The suspect LDAP, Smb.conf [global] section configuration. The Question What can I do? I've googled a lot, but still have no answer. Slow smb.conf WITH LDAP [global] workgroup = zmartsoft.local passdb backend = ldapsam:ldap://127.0.0.1 printing = cups printcap name = cups printcap cache time = 750 cups options = raw map to guest = Bad User logon path = \\%L\profiles\.msprofile logon home = \\%L\%U\.9xprofile logon drive = P: usershare allow guests = Yes add machine script = /usr/sbin/useradd -c Machine -d /var/lib/nobody -s /bin/false %m$ domain logons = Yes domain master = Yes local master = Yes netbios name = server os level = 65 preferred master = Yes security = user wins support = Yes idmap backend = ldap:ldap://127.0.0.1 ldap admin dn = cn=Administrator,dc=zmartsoft,dc=local ldap group suffix = ou=Groups ldap idmap suffix = ou=Idmap ldap machine suffix = ou=Machines ldap passwd sync = Yes ldap ssl = Off ldap suffix = dc=zmartsoft,dc=local ldap user suffix = ou=Users

  Read the article

• Verizon 4G LTE vs. a LAN

  - by n8wrl

  I have been having quite a bit of trouble getting my new Verizon 4G-LTE service running on a Windows 7 desktop. My desktop is on a LAN here at home with two other PC's. We all share printers, files, media, etc. Until yesterday, we also shared a Verizon 3G modem via a NetGear 3G broadband WAP. That isn't compatible with the 4G so now I am just trying to get the 4G modem working directly connected to one of the desktops. After some USB wrangling, it seems to work. Except, every 7-10 minutes the connection would drop. After some time on the phone with a very nice Verizon technician, it seems to be staying up - it's been up for 20 minutes now. He told me that my LAN was causing the 4G to drop. That traffic on my LAN, even though it is not destined for the internet (ICS not working yet) was causing the cell tower to detect an 'IP change' and a 'security violation' in my modem and drop my connection. Is this Verizon's way of forbidding more than one computer to share a modem? I have my computer running now without a LAN connection and the 4G is still up. But this isn't practical. Has anyone heard of this?

  Read the article

• Performance: Nginx SSL slowness or just SSL slowness in general?

  - by Mauvis Ledford

  I have an Amazon Web Services setup with an Apache instance behind Nginx with Nginx handling SSL and serving everything but the .php pages. In my ApacheBench tests I'm seeing this for my most expensive API call (which cache via Memcached): 100 concurrent calls to API call (http): 115ms (median) 260ms (max) 100 concurrent calls to API call (https): 6.1s (median) 11.9s (max) I've done a bit of research, disabled the most expensive SSL ciphers and enabled SSL caching (I know it doesn't help in this particular test.) Can you tell me why my SSL is taking so long? I've set up a massive EC2 server with 8CPUs and even applying consistent load to it only brings it up to 50% total CPU. I have 8 Nginx workers set and a bunch of Apache. Currently this whole setup is on one EC2 box but I plan to split it up and load balance it. There have been a few questions on this topic but none of those answers (disable expensive ciphers, cache ssl, seem to do anything.) Sample results below: $ ab -k -n 100 -c 100 https://URL This is ApacheBench, Version 2.3 <$Revision: 655654 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/ Benchmarking URL.com (be patient).....done Server Software: nginx/1.0.15 Server Hostname: URL.com Server Port: 443 SSL/TLS Protocol: TLSv1/SSLv3,AES256-SHA,2048,256 Document Path: /PATH Document Length: 73142 bytes Concurrency Level: 100 Time taken for tests: 12.204 seconds Complete requests: 100 Failed requests: 0 Write errors: 0 Keep-Alive requests: 0 Total transferred: 7351097 bytes HTML transferred: 7314200 bytes Requests per second: 8.19 [#/sec] (mean) Time per request: 12203.589 [ms] (mean) Time per request: 122.036 [ms] (mean, across all concurrent requests) Transfer rate: 588.25 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 65 168 64.1 162 268 Processing: 385 6096 3438.6 6199 11928 Waiting: 379 6091 3438.5 6194 11923 Total: 449 6264 3476.4 6323 12196 Percentage of the requests served within a certain time (ms) 50% 6323 66% 8244 75% 9321 80% 9919 90% 11119 95% 11720 98% 12076 99% 12196 100% 12196 (longest request)

  Read the article

< Previous Page | 38 39 40 41 42 43 44 45 46 47 48 49  | Next Page >