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• Implementing crossover in genetic programming

  - by Name

  Hi, I'm writing a genetic programming (GP) system (in C but that's a minor detail). I've read a lot of the literature (Koza, Poli, Langdon, Banzhaf, Brameier, et al) but there are some implementation details I've never seen explained. For example: I'm using a steady state population rather than a generational approach, primarily to use all of the computer's memory rather than reserve half for the interim population. Q1. In GP, as opposed to GA, when you perform crossover you select two parents but do you create one child or two, or is that a free choice you have? Q2. In steady state GP, as opposed to a generational system, what members of the population do the children created by crossover replace? This is what I haven't seen discussed. Is it the two parents, or is it two other, randomly-selected members? I can understand if it's the latter, and that you might use negative tournament selection to choose members to replace, but would that not create premature convergence? (After a crossover event the population contains the two original parents plus two children of those parents, and two other random members get removed. Elitism is inherent.) Q3. Is there a Web forum or mailing list focused on GP? Oddly I haven't found one. Yahoo's GP group is used almost exclusively for announcements, the Poli/Langdon Field Guide forum is almost silent, and GP discussions on general/game programming sites like gamedev.net are very basic. Thanks for any help you can provide!

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• Optimized Publish/Subcribe JMS Broker Cluster and Conflicting Posts on StackOverFlow for the Answer

  - by Gene

  Hi, I am looking to build a publish/subscribe distributed messaging framework that can manage huge volumes of message traffic with some intelligence at the broker level. I don't know if there's a topology that describes this, but this is the model I'm going after: EXAMPLE MODEL A A) There are two running message brokers (ideally all on localhost if possible, for easier demo-ing) : Broker-A Broker-B B) Each broker will have 2 listeners and 1 publisher. Example Figure [subscriber A1, subscriber A2, publisher A1] <-- BrokerA <-- BrokerB <-- [publisher B1, subscriber B1, subscriber B2] IF a message-X is published to broker A and there no subscribers for it among the listeners on Broker-B (via criteria in Message Selectors or Broker routing rules), then that message-X will never be published to Broker-B. ELSE, broker A will publish the message to broker B, where one of the broker B listeners/subscribers/services is expecting that message based on the subscription criteria. Is Clustering the Correct Approach? At first, I concluded that the "Broker Clustering" concept is what I needed to support this. However, as I have come to understand it, the typical use of clustering entails either: message redundancy across all brokers ... or Competing Consumers pattern ... and neither of these satisfy the requirement in the EXAMPLE MODEL A. What is the Correct Approach? My question is, does anyone know of a JMS implementation that supports the model I described? I scanned through all the stackoverflow post titles for the search: JMS and Cluster. I found these two informative, but seemingly conflicting posts: Says the EXAMPLE MODEL A is/should-be implicitly supported: http://stackoverflow.com/questions/2255816/jms-consumer-with-activemq-network-of-brokers " this means you pick a broker, connect to it, and let the broker network sort it out amongst themselves. In theory." Says the EXAMPLE MODEL A IS NOT suported: http://stackoverflow.com/questions/2017520/how-does-a-jms-topic-subscriber-in-a-clustered-application-server-recieve-message "All the instances of PropertiesSubscriber running on different app servers WILL get that message." Any suggestions would be greatly appreciated. Thanks very much for reading my post, Gene

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• How can I build something like Amazon S3 in Perl?

  - by Joel G

  I am looking to code a file storage application in perl similar to amazon s3. I already have a amazon s3 clone that I found online called parkplace but its in ruby and is old also isn't built for high loads. I am not really sure what modules and programs I should use so id like some help picking them out. My requirements are listed below (yes I know there are lots but I could start simple then add more once I get it going): Easy API implementation for client side apps. (maybe REST (?) Centralized database server for the USERDB (maybe PostgreSQL (?). Logging of all connections, bandwidth used, well pretty much everything to a centralized server (maybe PostgreSQL again (?). Easy server side configuration (config file(s) stored on the servers). Web based control panel for admin(s) and user(s) to show logs. (could work just running queries from the databases) Fast High Uptime Low memory usage Some sort of load distribution/load balancer (maybe a dns based or pound or perlbal or something else (?). Maybe a cache of some sort (memcached or parlbal or something else (?). Thanks in advance

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• Graph limitations - Should I use Decorator?

  - by Nick Wiggill

  I have a functional AdjacencyListGraph class that adheres to a defined interface GraphStructure. In order to layer limitations on this (eg. acyclic, non-null, unique vertex data etc.), I can see two possible routes, each making use of the GraphStructure interface: Create a single class ("ControlledGraph") that has a set of bitflags specifying various possible limitations. Handle all limitations in this class. Update the class if new limitation requirements become apparent. Use the decorator pattern (DI, essentially) to create a separate class implementation for each individual limitation that a client class may wish to use. The benefit here is that we are adhering to the Single Responsibility Principle. I would lean toward the latter, but by Jove!, I hate the decorator Pattern. It is the epitome of clutter, IMO. Truthfully it all depends on how many decorators might be applied in the worst case -- in mine so far, the count is seven (the number of discrete limitations I've recognised at this stage). The other problem with decorator is that I'm going to have to do interface method wrapping in every... single... decorator class. Bah. Which would you go for, if either? Or, if you can suggest some more elegant solution, that would be welcome. EDIT: It occurs to me that using the proposed ControlledGraph class with the strategy pattern may help here... some sort of template method / functors setup, with individual bits applying separate controls in the various graph-canonical interface methods. Or am I losing the plot?

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• WebFaultException http status code is not passed

  - by Mike Bantegui

  I have the following service method: <OperationContract()> <WebGet([ResponseFormat]:=WebMessageFormat.Json)> Function ShouldThrowException() As Boolean It's implementation does only one thing, which is to throw a WebFaultException. Public Function ShouldThrowException() As Boolean Implements IRestService.ShouldThrowException Throw New WebFaultException(Of String)("This should fail", HttpStatusCode.BadRequest) End Function My web.config reads as: <endpointBehaviors> <behavior name="WebEndpointBehavior"> <webHttp /> </behavior> </endpointBehaviors> .. snip .. <webHttpBinding> <binding name="WebBinding" crossDomainScriptAccessEnabled="true"> <security mode="None" /> </binding> </webHttpBinding> .. snip .. <service name="RestService"> <endpoint address="" binding="webHttpBinding" behaviorConfiguration="WebEndpointBehavior" bindingConfiguration="WebBinding" contract="IRestService" name="RestService"> </endpoint> </service> When I call ShouldThrowException via my browser, I only get the following: "This should fail" I was expecting to get a 400 Bad Request error on the page. If I inspect the page using FireBug, I see that the HTTP status code that was returned is a 200 OK. According to this blog post, I should be seeing this exception. Except I'm not. What am I doing wrong here?

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• Basic jUnit Questions

  - by Epitaph

  I was testing a String multiplier class with a multiply() method that takes 2 numbers as inputs (as String) and returns the result number (as String) `public String multiply(String num1, String num2); I have done the implementation and created a test class with the following test cases involving the input String parameter as 1) valid numbers 2) characters 3) special symbol 4) empty string 5) Null value 6) 0 7) Negative number 8) float 9) Boundary values 10) Numbers that are valid but their product is out of range 11) numbers will + sign (+23) 1) I'd like to know if "each and every" assertEquals() should be in it's own test method? Or, can I group similar test cases like testInvalidArguments() to contains all asserts involving invalid characters since ALL of them throw the same NumberFormatException ? 2) If testing an input value like character ("a"), do I need to include test cases for ALL scenarios? "a" as the first argument "a" as the second argument "a" and "b" as the 2 arguments 3) As per my understanding, the benefit of these unit tests is to find out the cases where the input from a user might fail and result in an exception. And, then we can give the user with a meaningful message (asking them to provide valid input) instead of an exception. Is that the correct? And, is it the only benefit? 4) Are the 11 test cases mentioned above sufficient? Did I miss something? Did I overdo? When is enough? 5) Following from the above point, have I successfully tested the multiply() method?

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• Boost.Python wrapping hierarchies avoiding diamond inheritance

  - by stbuton

  I'm having some trouble seeing what the best way to wrap a series of classes with Boost.Python while avoiding messy inheritance problems. Say I have the classes A, B, and C with the following structure: struct A { virtual void foo(); virtual void bar(); virtual void baz(); }; struct B : public A { virtual void quux(); }; struct C : public A { virtual void foobar(); }; I want to wrap all classes A, B, and C such that they are extendable from Python. The normal method for accomplishing this would be along the lines of: struct A_Wrapper : public A, boost::python::wrapper<A> { //dispatch logic for virtual functions }; Now for classes B and C which extend from A I would like to be able to inherit and share the wrapping implementation for A. So I'd like to be able to do something along the lines of: struct B_Wrapper : public B, public A_Wrapper, public boost::python::wrapper<B> { //dispatch logic specific for B }; struct C_Wrapper : public C, public A_Wrapper, public boost::python::wrapper<C> { //dispatch logic specific for C } However, it seems like that would introduce all manner of nastiness with the double inheritance of the boost wrapper base and the double inheritance of A in the B_Wrapper and C_Wrapper objects. Is there a common way that this instance is solved that I'm missing? thanks.

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• Vimeo Desktop App OAuth

  - by Barry

  Hi Guys, I'm currently having massive trouble with Vimeo's Oauth implementation and my desktop app. My program does the following correctly. 1- Requests a Unauthorized Request Token with my key and secret and returns - a Token and a Token secret. 2- Generates a URL for the user to go to using the token which then shows our application's name and allows the user to Authorize us to use his/her account. It then shows a verifier which the user returns and puts into our app. The problem is the third step and actually exchanging the tokens for the access tokens. Basically every time we try and get them we get a "Invalid / expired token - The oauth_token passed was either not valid or has expired" I looked at the documentation and there's supposed to be a callback to a server when deployed like that which gives the user an "authorized token" but as im developing a desktop app we can't do this. So I assume the token retrieved in 1 is valid for this step. (actually it seems it is: http://vimeo.com/forums/topic:22605) So I'm wondering now am I missing something here on my actual vimeo application account now? is it treating it as a web hosted app with callbacks? all the elements are there for this to work and I've used this same component to create a twitter Oauth login in exactly the same way and it was fine. Thanks in advance, Barry

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• Detecting Xml namespace fast

  - by Anna Tjsoken

  Hello there, This may be a very trivial problem I'm trying to solve, but I'm sure there's a better way of doing it. So please go easy on me. I have a bunch of XSD files that are internal to our application, we have about 20-30 Xml files that implement datasets based off those XSDs. Some Xml files are small (<100Kb), others are about 3-4Mb with a few being over 10Mb. I need to find a way of working out what namespace these Xml files are in order to provide (something like) intellisense based off the XSD. The implementation of this is not an issue - another developer has written the code for this. But I'm not sure the best (and fastest!) way of detecting the namespace is without the use of XmlDocument (which does a full parse). I'm using C# 3.5 and the documents come through as a Stream (some are remote files). All the files are *.xml (I can detect if it was extension based) but unfortunately the Xml namespace is the only way. Right now I've tried XmlDocument but I've found it to be innefficient and slow as the larger documents are awaiting to be parsed (even the 100Kb docs). public string GetNamespaceForDocument(Stream document); Something like the above is my method signature - overloads include string for "content". Would a RegEx (compiled) pattern be good? How does Visual Studio manage this so efficiently? Another college has told me to find a fast Xml parser in C/C++, parse the content and have a stub that gives back the namespace as its slower in .NET, is this a good idea?

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• How to build n-layered web architecture with PHP?

  - by Alex

  I have a description and design of a website and I need to redesign it to allow for new requirements. The website's purpose is the offering of government's contracts and bidding opportunities for different businesses.I'm dealing with the 3-tier architecture PHP website comprising of the user-interface tier(client's web browser),business logic layer(Apache web server with PHP engine in it and a couple of applications running within a web server as well) and a database layer(local mysql database). Now,i need to redesign it to su???rt distributed n-tier architecture and specify how I would go about it.After long hours of research i came to this solution: business logic should be separated into presentation and purely business logic tier to allow for n-layer architecture(user-interface,presentation tier,b.logic and data tier).I have decided to use ??? just for the presentation(since the original existing website is in PHP) and use it within apache web server.In the business logic i want to use J2?? implementation technology instead of implementing it in PHP(i.e using Zend app.server and smarty template) cz J2EE can provide much more essential container services which are essential for business logic,its robustness,maintainability and different critical business operations which will be carried out by the g?v?rnment's website.So,particularly,i want to use J??ss app.server with ?J? business objects in it which would provide all the b.logic in java and would interact with the database and so forth.In order to connect PHP on a web server with java on app.server i'm gonna use PHP/Java bridge API (or maybe Quercus or SOAP is better?).Finally,i have my data tier with mysql which will communicate with b.logic via JD??.Payment system application in ???.server is gonna use S??? to talk with credit card company. From your professional point of view,does it sound like a good way of redesigning the original website to allow for n-tier architecture considering the specifics of the website and the criticality of its operations?(payment system is included in it)or u would personally prefer to use PHP business objects for business logic as well instead of J2EE?If you have any wiser recommendation or some alternative,please let me know what is right or wrong in my current solution. H??? to hear your professional advice very s??n (I'm new to the area of web development) Thanks in advance

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• Implementing the ‘defer’ statement from Go in Objective-C?

  - by zoul

  Hello! Today I read about the defer statement in the Go language: A defer statement pushes a function call onto a list. The list of saved calls is executed after the surrounding function returns. Defer is commonly used to simplify functions that perform various clean-up actions. I thought it would be fun to implement something like this in Objective-C. Do you have some idea how to do it? I thought about dispatch finalizers, autoreleased objects and C++ destructors. Autoreleased objects: @interface Defer : NSObject {} + (id) withCode: (dispatch_block_t) block; @end @implementation Defer - (void) dealloc { block(); [super dealloc]; } @end #define defer(__x) [Defer withCode:^{__x}] - (void) function { defer(NSLog(@"Done")); … } Autoreleased objects seem like the only solution that would last at least to the end of the function, as the other solutions would trigger when the current scope ends. On the other hand they could stay in the memory much longer, which would be asking for trouble. Dispatch finalizers were my first thought, because blocks live on the stack and therefore I could easily make something execute when the stack unrolls. But after a peek in the documentation it doesn’t look like I can attach a simple “destructor” function to a block, can I? C++ destructors are about the same thing, I would create a stack-based object with a block to be executed when the destructor runs. This would have the ugly disadvantage of turning the plain .m files into Objective-C++? I don’t really think about using this stuff in production, I’m just interested in various solutions. Can you come up with something working, without obvious disadvantages? Both scope-based and function-based solutions would be interesting.

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• How to mmap the stack for the clone() system call on linux?

  - by Joseph Garvin

  The clone() system call on Linux takes a parameter pointing to the stack for the new created thread to use. The obvious way to do this is to simply malloc some space and pass that, but then you have to be sure you've malloc'd as much stack space as that thread will ever use (hard to predict). I remembered that when using pthreads I didn't have to do this, so I was curious what it did instead. I came across this site which explains, "The best solution, used by the Linux pthreads implementation, is to use mmap to allocate memory, with flags specifying a region of memory which is allocated as it is used. This way, memory is allocated for the stack as it is needed, and a segmentation violation will occur if the system is unable to allocate additional memory." The only context I've ever heard mmap used in is for mapping files into memory, and indeed reading the mmap man page it takes a file descriptor. How can this be used for allocating a stack of dynamic length to give to clone()? Is that site just crazy? ;) In either case, doesn't the kernel need to know how to find a free bunch of memory for a new stack anyway, since that's something it has to do all the time as the user launches new processes? Why does a stack pointer even need to be specified in the first place if the kernel can already figure this out?

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• Using Fantom USB Driver from JNI

  - by Starky

  I'm having some difficulty with JNI. I'm using JNI to call some Java methods from a C++ program. This implementation of JNI is working fine. The goal of the Java program is to send commands over USB to a LEGO robot using LEJOS. This works fine when running the Java program by itself but for some reason when I call the methods from C++ the robot cannot be detected. My only lead so far is that there may be some problem using the Fantom USB driver from a JNI call. This is the driver that's used for the USB connection to the robot. I've had a quick look at the code for the driver and it looks like it makes use of JNI too. So I guess I'm asking the following things: What differences could there be between calling code from JNI and executing it through command prompt with the 'java classname args' method which could cause this problem? Could it be that there is some problem with me using JNI in C++ when the driver that's being used uses JNI as well? I won't post any code just now as I don't think it's really relevant but if anyone thinks that they need to see it then I can add it.

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• Converting From Castle Windsor To StructureMap In An MVC2 Project

  - by alphadogg

  I am learning about best practices in MVC2 and I am knocking off a copy of the "Who Can Help Me" project (http://whocanhelpme.codeplex.com/) off Codeplex. In it, they use Castle Windsor for their DI container. One "learning" task I am trying to do is convert this subsystem in this project to use StructureMap. Basically, at Application_Start(), the code news up a Windsor container. Then, it goes through multiple assemblies, using MEF: public static void Register(IContainer container) { var catalog = new CatalogBuilder() .ForAssembly(typeof(IComponentRegistrarMarker).Assembly) .ForMvcAssembly(Assembly.GetExecutingAssembly()) .ForMvcAssembliesInDirectory(HttpRuntime.BinDirectory, "CPOP*.dll") // Won't work in Partial trust .Build(); var compositionContainer = new CompositionContainer(catalog); compositionContainer .GetExports<IComponentRegistrar>() .Each(e => e.Value.Register(container)); } and any class in any assembly that has an IComponentRegistrar interface will get its Register() method run. For example, the controller registrar's Register() method implementation basically is: public void Register(IContainer container) { Assembly.GetAssembly(typeof(ControllersRegistrarMarker)).GetExportedTypes() .Where(IsController) .Each(type => container.AddComponentLifeStyle( type.Name.ToLower(), type, LifestyleType.Transient )); } private static bool IsController(Type type) { return typeof(IController).IsAssignableFrom(type); } Hopefully, I am not butchering WCHM too much. I am wondering how does one do this with StructureMap?

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• python: how to design a container with elements that must reference their container

  - by Luke404

  (the title is admittedly not that great. Please forgive my English, this is the best I could think of) I'm writing a python script that will manage email domains and their accounts, and I'm also a newby at OOP design. My two (related?) issues are: the Domain class must do special work to add and remove accounts, like adding/removing them to the underlying implementation how to manage operations on accounts that must go through their container To solve the former issue I'd add a factory method to the Domain class that'll build an Account instance in that domain, and a 'remove' (anti-factory?) method to handle deletions. For the latter this seems to me "anti-oop" since what would logically be an operation on an Account (eg, change password) must always reference the containing Domain. Seems to me that I must add to the Account a reference back to the Domain and use that to get data (like the domain name) or call methods on the Domain class. Code example (element uses data from the container) that manages an underlying Vpopmail system: class Account: def __init__(self, name, password, domain): self.name = name self.password = password self.domain = domain def set_password(self, password): os.system('vpasswd %s@%s %s' % (self.name, self.domain.name, password) self.password = password class Domain: def __init__(self, domain_name): self.name = domain_name self.accounts = {} def create_account(self, name, password): os.system('vadduser %s@%s %s' % (name, self.name, password)) account = Account(name, password, self) self.accounts[name] = account def delete_account(self, name): os.system('vdeluser %s@%s' % (name, self.name)) del self.accounts[name] another option would be for Account.set_password to call a Domain method that would do the actual work - sounds equally ugly to me. Also note the duplication of data (account name also as dict key), it sounds logical (account names are "primary key" inside a domain) but accounts need to know their own name.

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• How should I go about implementing a points-to analysis in Maude?

  - by reprogrammer

  I'm going to implement a points-to analysis algorithm. I'd like to implement this analysis mainly based on the algorithm by Whaley and Lam. Whaley and Lam use a BDD based implementation of Datalog to represent and compute the points-to analysis relations. The following lists some of the relations that are used in a typical points-to analysis. Note that D(w, z) :- A(w, x),B(x, y), C(y, z) means D(w, z) is true if A(w, x), B(x, y), and C(y, z) are all true. BDD is the data structure used to represent these relations. Relations input vP0 (variable : V, heap : H) input store (base : V, field : F, source : V) input load (base : V, field : F, dest : V) input assign (dest : V, source : V) output vP (variable : V, heap : H) output hP (base : H, field : F, target : H) Rules vP(v, h) :- vP0(v, h) vP(v1, h) :- assign(v1, v2), vP(v2, h) hP(h1, f,h2) :- store(v1, f, v2), vP(v1, h1), vP(v2, h2) vP(v2, h2) :- load(v1, f, v2), vP(v1, h1), hP(h1, f, h2) I need to understand if Maude is a good environment for implementing points-to analysis. I noticed that Maude uses a BDD library called BuDDy. But, it looks like that Maude uses BDDs for a different purpose, i.e. unification. So, I thought I might be able to use Maude instead of a Datalog engine to compute the relations of my points-to analysis. I assume Maude propagates independent information concurrently. And this concurrency could potentially make my points-to analysis faster than sequential processing of rules. But, I don't know the best way to represent my relations in Maude. Should I implement BDD in Maude myself, or Maude's internal unification based on BDD has the same effect?

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• How do I read the manifest file for a webapp running in apache tomcat?

  - by Nik Reiman

  I have a webapp which contains a manifest file, in which I write the current version of my application during an ant build task. The manifest file is created correctly, but when I try to read it in during runtime, I get some strange side-effects. My code for reading in the manifest is something like this: InputStream manifestStream = Thread.currentThread() .getContextClassLoader() .getResourceAsStream("META-INFFFF/MANIFEST.MF"); try { Manifest manifest = new Manifest(manifestStream); Attributes attributes = manifest.getMainAttributes(); String impVersion = attributes.getValue("Implementation-Version"); mVersionString = impVersion; } catch(IOException ex) { logger.warn("Error while reading version: " + ex.getMessage()); } When I attach eclipse to tomcat, I see that the above code works, but it seems to get a different manifest file than the one I expected, which I can tell because the ant version and build timestamp are both different. Then, I put "META-INFFFF" in there, and the above code still works! This means that I'm reading some other manifest, not mine. I also tried this.getClass().getClassLoader().getResourceAsStream(...) But the result was the same. What's the proper way to read the manifest file from inside of a webapp running in tomcat? Edit: Thanks for the suggestions so far. Also, I should note that I am running tomcat standalone; I launch it from the command line, and then attach to the running instance in Eclipse's debugger. That shouldn't make a difference, should it?

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• Normalizing (webdav) unicode paths

  - by Evert

  Hi guys, I'm working on a WebDAV implementation for PHP. In order to make it easier for Windows and other operating systems to work together, I need jump through some character encoding hoops. Windows uses ISO-8859-1 in it's HTTP request, while most other clients encode anything beyond ascii as UTF-8. My first approach was to ignore this altogether, but I quickly ran into issues when returning urls. I then figured it's probably best to normalize all urls. Using u¨ as an example. This will get sent over the wire by OS/X as u%CC%88 (this is codepoint U+0308) Windows sents this as: %FC (latin1) But, doing a utf8_encode on %FC, I get : %C3%BC (this is codepoint U+00FC) Should I treat %C3%BC and u%CC%88 as the same thing? If so.. how? Not touching it seems to work OK for windows. It somehow understands that it's a unicode character, but updating the same file throws an error (for no particular reason). I'd be happy to provide more information.

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• Java Access Token PKCS11 Not found Provider

  - by oracleruiz

  Hello I'm trying to access the keystore from my smartcard in Java. And I'm using the following code.. I'm using the Pkcs11 implementation of OpenSc http://www.opensc-project.org/opensc File windows.cnf = name=dnie library=C:\WINDOWS\system32\opensc-pkcs11.dll Java Code = String configName = "windows.cnf" String PIN = "####"; Provider p = new sun.security.pkcs11.SunPKCS11(configName); Security.addProvider(p); KeyStore keyStore = KeyStore.getInstance("PKCS11", "SunPKCS11-dnie"); =)(= char[] pin = PIN.toCharArray(); keyStore.load(null, pin); When the execution goes by the line with =)(= throws me the following exeption java.security.KeyStoreException: PKCS11 not found at java.security.KeyStore.getInstance(KeyStore.java:635) at ObtenerDatos.LeerDatos(ObtenerDatos.java:52) at ObtenerDatos.obtenerNombre(ObtenerDatos.java:19) at main.main(main.java:27) Caused by: java.security.NoSuchAlgorithmException: no such algorithm: PKCS11 for provider SunPKCS11-dnie at sun.security.jca.GetInstance.getService(GetInstance.java:70) at sun.security.jca.GetInstance.getInstance(GetInstance.java:190) at java.security.Security.getImpl(Security.java:662) at java.security.KeyStore.getInstance(KeyStore.java:632) I think the problem is "SunPKCS11-dnie", but I don't know to put there. I had tried with a lot of combinations... Anyone can help me...

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• Autodetect Presence of CSV Headers in a File

  - by banzaimonkey

  Short question: How do I automatically detect whether a CSV file has headers in the first row? Details: I've written a small CSV parsing engine that places the data into an object that I can access as (approximately) an in-memory database. The original code was written to parse third-party CSV with a predictable format, but I'd like to be able to use this code more generally. I'm trying to figure out a reliable way to automatically detect the presence of CSV headers, so the script can decide whether to use the first row of the CSV file as keys / column names or start parsing data immediately. Since all I need is a boolean test, I could easily specify an argument after inspecting the CSV file myself, but I'd rather not have to (go go automation). I imagine I'd have to parse the first 3 to ? rows of the CSV file and look for a pattern of some sort to compare against the headers. I'm having nightmares of three particularly bad cases in which: The headers include numeric data for some reason The first few rows (or large portions of the CSV) are null There headers and data look too similar to tell them apart If I can get a "best guess" and have the parser fail with an error or spit out a warning if it can't decide, that's OK. If this is something that's going to be tremendously expensive in terms of time or computation (and take more time than it's supposed to save me) I'll happily scrap the idea and go back to working on "important things". I'm working with PHP, but this strikes me as more of an algorithmic / computational question than something that's implementation-specific. If there's a simple algorithm I can use, great. If you can point me to some relevant theory / discussion, that'd be great, too. If there's a giant library that does natural language processing or 300 different kinds of parsing, I'm not interested.

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• SQLite assembly not copied to output folder for unit testing

  - by Groo

  Problem: SQLite assembly referenced in my DAL assembly does not get copied to the output folder when doing unit tests (Copy local is set to true). I am working on a .Net 3.5 app in VS2008, with NHibernate & SQLite in my DAL. Data access is exposed through the IRepository interface (repository factory) to other layers, so there is no need to reference NHibernate or the System.Data.SQLite assemblies in other layers. For unit testing, there is a public factory method (also in my DAL) which creates an in-memory SQLite session and creates a new IRepository implementation. This is also done to avoid have a shared SQLite in-memory config for all assemblies which need it, and to avoid referencing those DAL internal assemblies. The problem is when I run unit tests which reside a separate project - if I don't add System.Data.SQLite as a reference to the unit test project, it doesn't get copied to the TestResults...\Out folder (although this project references my DAL project, which references System.Data.SQLite, which has its Copy local property set to true), so the tests fail while NHibernate is being configured. If I add the reference to my testing project, then it does get copied and unit tests work. What am I doing wrong?

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• WPF HiercharchicalDataTemplate.DataType: How to react on interfaces?

  - by David Schmitt

  Problem I've got a collection of IThings and I'd like to create a HierarchicalDataTemplate for a TreeView. The straightforward DataType={x:Type local:IThing} of course doesn't work, probably because the WPF creators didn't want to handle the possible ambiguities. Since this should handle IThings from different sources at the same time, referencing the implementing class is out of question. Current solution For now I'm using a ViewModel which proxies IThing through a concrete implementation: public interface IThing { string SomeString { get; } ObservableCollection<IThing> SomeThings { get; } // many more stuff } public class IThingViewModel { public IThing Thing { get; } public IThingViewModel(IThing it) { this.Thing = it; } } <!-- is never applied --> <HierarchicalDataTemplate DataType="{x:Type local:IThing}"> <!-- is applied, but looks strange --> <HierarchicalDataTemplate DataType="{x:Type local:IThingViewModel}" ItemsSource="{Binding Thing.SomeThings}"> <TextBox Text="{Binding Thing.SomeString}"/> </HierarchicalDataTemplate> Question Is there a better (i.e. no proxy) way?

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• Dividing sections inside an omp parallel for : OpenMP

  - by Sayan Ghosh

  Hi, I have a situation like: #pragma omp parallel for private(i, j, k, val, p, l) for (i = 0; i < num1; i++) { for (j = 0; j < num2; j++) { for (k = 0; k < num3; k++) { val = m[i + j*somenum + k*2] if (val != 0) for (l = start; l <= end; l++) { someFunctionThatWritesIntoGlobalArray((i + l), j, k, (someFunctionThatGetsValueFromAnotherArray((i + l), j, k) * val)); } } } for (p = 0; p < num4; p++) { m[p] = 0; } } Thanks for reading, phew! Well I am noticing a very minor difference in the results (0.999967[omp] against 1[serial]), when I use the above (which is 3 times faster) against the serial implementation. Now I know I am doing a mistake here...especially the connection between loops is evident. Is it possible to parallelize this using omp sections? I tried some options like making shared(p) {doing this, I got correct values, as in the serial form}, but there was no speedup then. Any general advice on handling openmp pragmas over a slew of for loops would also be great for me!

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• rails best practices where to place unobtrusive javascript

  - by nathanvda

  Hi there, my rails applications (all 2.3.5) use a total mix of inline javascript, rjs, prototype and jquery. Let's call it learning or growing pains. Lately i have been more and more infatuated with unobtrusive javascript. It makes your html clean, in the same way css cleaned it up. But most examples i have seen are small examples, and they put all javascript(jquery) inside application.js Now i have a pretty big application, and i am thinking up ways to structure my js. I like somehow that my script is still close to the view, so i am thinking something like orders.html.erb orders.js where orders.js contains the unobtrusive javascript specific to that view. But maybe that's just me being too conservative :) I have read some posts by Yehuda Katz about this very problem here and here, where he tackles this problem. It will go through your js-files and only load those relevant to your view. But alas i can't find a current implementation. So my questions: how do you best structure your unobtrusive javascript; manage your code, how do you make sure that it is obvious from the html what something is supposed to do. I guess good class names go a long way :) how do you arrange your files, load them all in? just a few? do you use content_for :script or javascript_include_tag in your view to load the relevant scripts. Or ... ? do you write very generic functions (like a delete), with parameters (add extra attributes?), or do you write very specific functions (DRY?). I know in Rails 3 there is a standard set, and everything is unobtrusive there. But how to start in Rails 2.3.5? In short: what are the best practices for doing unobtrusive javascript in rails? :)

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• (C#) Get index of current foreach iteration

  - by Graphain

  Hi, Is there some rare language construct I haven't encountered (like the few I've learned recently, some on Stack Overflow) in C# to get a value representing the current iteration of a foreach loop? For instance, I currently do something like this depending on the circumstances: int i=0; foreach (Object o in collection) { ... i++; } Answers: @bryansh: I am setting the class of an element in a view page based on the position in the list. I guess I could add a method that gets the CSSClass for the Objects I am iterating through but that almost feels like a violation of the interface of that class. @Brad Wilson: I really like that - I've often thought about something like that when using the ternary operator but never really given it enough thought. As a bit of food for thought it would be nice if you could do something similar to somehow add (generically to all IEnumerable objects) a handle on the enumerator to increment the value that an extension method returns i.e. inject a method into the IEnumerable interface that returns an iterationindex. Of course this would be blatant hacks and witchcraft... Cool though... @crucible: Awesome I totally forgot to check the LINQ methods. Hmm appears to be a terrible library implementation though. I don't see why people are downvoting you though. You'd expect the method to either use some sort of HashTable of indices or even another SQL call, not an O(N) iteration... (@Jonathan Holland yes you are right, expecting SQL was wrong) @Joseph Daigle: The difficulty is that I assume the foreach casting/retrieval is optimised more than my own code would be. @Jonathan Holland: Ah, cheers for explaining how it works and ha at firing someone for using it.

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