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• What's a good Java-based Master-Slave communication mechanism?

  - by plecong

  I'm creating a Java application that requires master-slave communication between JVMs, possibly residing on the same physical machine. There will be a "master" server running inside a JEE application server (i.e. JBoss) that will have "slave" clients connect to it and dynamically register itself for communication (that is the master will not know the IP addresses/ports of the slaves so cannot be configured in advance). The master server acts as a controller that will dole work out to the slaves and the slaves will periodically respond with notifications, so there would be bi-directional communication. I was originally thinking of RPC-based systems where each side would be a server, but it could get complicated, so I'd prefer a mechanism where there's an open socket and they talk back and forth. I'm looking for a communication mechanism that would be low-latency where the messages would be mostly primitive types, so no serious serialization is necessary. Here's what I've looked at: RMI JMS: Built-in to Java, the "slave" clients would connect to the existing ConnectionFactory in the application server. JAX-WS/RS: Both master and slave would be servers exposing an RPC interface for bi-directional communication. JGroups/Hazelcast: Use shared distributed data structures to facilitate communication. Memcached/MongoDB: Use these as "queues" to facilitate communication, though the clients would have to poll so there would be some latency. Thrift: This does seem to keep a persistent connection, but not sure how to integrate/embed a Thrift server into JBoss WebSocket/Raw Socket: This would work, but require a lot more custom code than I'd like. Is there any technology I'm missing? Edit: Also looked at: JMX: Have the client connect to JBoss' JMX server and receive JMX notifications for bidirectional comms.

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• Why won't this SQL CAST work?

  - by Kev

  I have a nvarchar(50) column in a SQL Server 2000 table defined as follows: TaskID nvarchar(50) NULL I need to fill this column with some random SQL Unique Identifiers (I am unable to change the column type to uniqueidentifier). I tried this: UPDATE TaskData SET TaskID = CAST(NEWID() AS nvarchar) but I got the following error: Msg 8115, Level 16, State 2, Line 1 Arithmetic overflow error converting expression to data type nvarchar. I also tried: UPDATE TaskData SET TaskID = CAST(NEWID() AS nvarchar(50)) but then got this error: Msg 8152, Level 16, State 6, Line 1 String or binary data would be truncated. I don't understand why this doesn't work but this does: DECLARE @TaskID nvarchar(50) SET @TaskID = CAST(NEW() AS nvarchar(50)) I also tried CONVERT(nvarchar, NEWID()) and CONVERT(nvarchar(50), NEWID()) but got the same errors.

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• GA written in Java

  - by EnderMB

  I am attempting to write a Genetic Algorithm based on techniques I had picked up from the book "AI Techniques for Game Programmers" that uses a binary encoding and fitness proportionate selection (also known as roulette wheel selection) on the genes of the population that are randomly generated within the program in a two-dimensional array. I recently came across a piece of pseudocode and have tried to implement it, but have come across some problems with the specifics of what I need to be doing. I've checked a number of books and some open-source code and am still struggling to progress. I understand that I have to get the sum of the total fitness of the population, pick a random number between the sum and zero, then if the number is greater than the parents to overwrite it, but I am struggling with the implementation of these ideas. Any help in the implementation of these ideas would be very much appreciated as my Java is rusty.

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• Haskell optimization of a function looking for a bytestring terminator

  - by me2

  Profiling of some code showed that about 65% of the time I was inside the following code. What it does is use the Data.Binary.Get monad to walk through a bytestring looking for the terminator. If it detects 0xff, it checks if the next byte is 0x00. If it is, it drops the 0x00 and continues. If it is not 0x00, then it drops both bytes and the resulting list of bytes is converted to a bytestring and returned. Any obvious ways to optimize this? I can't see it. parseECS = f [] False where f acc ff = do b <- getWord8 if ff then if b == 0x00 then f (0xff:acc) False else return $ L.pack (reverse acc) else if b == 0xff then f acc True else f (b:acc) False

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• Xcode5 post-archive script for Sparkle package no longer works

  - by Flyingdiver

  Xcode 5 seems to have changed the way it stores the build application package (xxx.app) such that ditto no longer works. In the ../BuildProductsPath/Release/ directory, the app is actually a symlink to .../InstallationBuildProductsLocation/Applications/... MyApp.app - ~/Library/Developer/Xcode/DerivedData/MyApp-emwilkqhlayanxahjpexlpbbkato/Build/Intermediates/ArchiveIntermediates/MyApp/InstallationBuildProductsLocation/Applications/MyApp This breaks the ditto command I was using to create a zip file of the application to put on my Sparkle update server. Anyone have an updated script for building the Sparkle XML and ZIP files? Or know what environment variable I need to use to locate my actual binary after the Archive phase?

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• Working with complex objects in Prevayler commands

  - by alexantd

  The demos included in the Prevayler distribution show how to pass in a couple strings (or something simple like that) into a command constructor in order to create or update an object. The problem is that I have an object called MyObject that has a lot of fields. If I had to pass all of them into the CreateMyObject command manually, it would be a pain. So an alternative I thought of is to pass my business object itself into the command, but to hang onto a clone of it (keeping in mind that I can't store the BO directly in the command). Of course after executing this command, I would need to make sure to dispose of the original copy that I passed in. public class CreateMyObject implements TransactionWithQuery { private MyObject object; public CreateMyObject(MyObject business_obj) { this.object = (MyObject) business_obj.clone(); } public Object executeAndQuery(...) throws Exception { ... } } The Prevayler wiki says: Transactions can't carry direct object references (pointers) to business objects. This has become known as the baptism problem because it's a common beginner pitfall. Direct object references don't work because once a transaction has been serialized to the journal and then deserialized for execution its object references no longer refer to the intended objects - - any objects they may have referred to at first will have been copied by the serialization process! Therefore, a transaction must carry some kind of string or numeric identifiers for any objects it wants to refer to, and it must look up the objects when it is executed. I think by cloning the passed-in object I will be getting around the "direct object pointer" problem, but I still don't know whether or not this is a good idea...

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• Why does this crash?

  - by Adam Driscoll

  I've been banging my head...I can't pretend to be a C++ guy... TCHAR * pszUserName = userName.GetBuffer(); SID sid; SecureZeroMemory(&sid, sizeof(sid)); SID_NAME_USE sidNameUse; DWORD cbSid = sizeof(sid); pLog->Log(_T("Getting the SID for user [%s]"), 1, userName); if (!LookupAccountName(NULL, (LPSTR)pszUserName, &sid, &cbSid, NULL, 0, &sidNameUse)) { pLog->Log(_T("Failed to look up user SID. Error code: %d"),1, GetLastError()); return _T(""); } pLog->Log(_T("Converting binary SID to string SID")); The message 'Getting the SID for user [x] is written' but then the app crashes. I'm assuming is was the LookupAccountName call. EDIT: Whoops userName is a MFC CString

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• Boost Date_Time problem compiling a simple program

  - by Andry

  Hello! I'm writing a very stupid program using Boost Date_Time library. int main(int srgc, char** argv) { using namespace boost::posix_time; date d(2002,Feb,1); //an arbitrary date ptime t1(d, hours(5)+nanosec(100)); //date + time of day offset ptime t2 = t1 - minutes(4)+seconds(2); ptime now = second_clock::local_time(); //use the clock date today = now.date(); //Get the date part out of the time } Well I cannot compile it, compiler does not recognize a type... Well I used many features of Boost libs like serialization and more... I correctly built them and, looking in my /usr/local/lib folder I can see that libboost_date_time.so is there (a good sign which means I was able to build that library) When I compile I write the following: g++ -lboost_date_time main.cpp But the errors it showed me when I specify the lib are the same of those ones where I do not specify any lib. What is this? Anyone knows? The error is main.cpp: In function ‘int main(int, char**)’: main.cpp:9: error: ‘date’ was not declared in this scope main.cpp:9: error: expected ‘;’ before ‘d’ main.cpp:10: error: ‘d’ was not declared in this scope main.cpp:10: error: ‘nanosec’ was not declared in this scope main.cpp:13: error: expected ‘;’ before ‘today’

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• How to marshal structs with unknown length string fields in C#

  - by Ofir

  Hi all, I get an array of bytes, I need to unmarshal it to C# struct. I know the type of the struct, it has some strings fields. The strings in the byte array appears as so: two first bytes are the length of the string, then the string itself. I don;t know the length of the strings. I do know that its Unicode! [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)] public class User { int Id;//should be 1 String UserName;//should be OFIR String FullName;//should be OFIR } the byte array looks like so: 00,00,01,00, 00,00,08,00, 4F,00,46,00,49,00,52,00, 00,00,08,00, 4F,00,46,00,49,00,52,00, I also found this link with same problem unsolved: loading binary data into a structure Thank you all, Ofir

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• C++ template class error with operator ==

  - by Tommy

  Error: error C2678: binary '==' : no operator found which takes a left-hand operand of type 'const entry' (or there is no acceptable conversion) The function: template <class T, int maxSize> int indexList<T, maxSize>::search(const T& target) const { for (int i = 0; i < maxSize; i++) if (elements[i] == target) //ERROR??? return i; // target found at position i // target not found return -1; } indexList.h indexList.cpp Is this suppose to be an overloaded operator? Being a template class I am not sure I understand the error? Solution- The overload function in the class now declared const: //Operators bool entry::operator == (const entry& dE) const <-- { return (name ==dE.name); }

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• openCV usage cvFindDominantPoints

  - by rsinha

  Hi, Does anyone know how to use the cvFindDominantPoints API of openCV? I basically have a 1 channel, binary image from which I get a set of contours. Judging from the image, I seem to be getting the correct contours. Now, I am selecting one of these contours to get dominant points of. This contour has about 60 vertices. However, the API call to cvFindDominantPoints is giving me a sequence of points (about 15) that does not even lie on the contour. It is quite far from it. Any insight? my usage: CvSeq *dominantpoints = cvFindDominantPoints(targetSeq, tristorage, CV_DOMINANT_IPAN, 7, 9, 9, 150);

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• How to interpret mono profiler results?

  - by Ovidiu Pacurar

  I created a console application in C# and running it on windows/.NET is 5x faster than on linux/mono or windows/mono. The app encodes some binary files into text format(JSON). I profiled the app on linux/mono using: mono --profile=default:stat myconsoleapp.exe Here is the first part of the result: prof counts: total/unmanaged: 32274/25062 23542 72.95 % mono 459 1.42 % System.Decimal:Divide (System.Decimal,System.Decimal) 457 1.42 % System.Decimal:Round (System.Decimal,int,System.MidpointRounding) 411 1.27 % /lib/libz.so.1 262 0.81 % /lib/tls/i686/cmov/libc.so.6(memmove 253 0.78 % System.Decimal:IsZero () 247 0.77 % System.NumberFormatter:Init (string,double,int) 213 0.66 % System.NumberFormatter:AppendDigits (int,int) 72.95 % mono? Are mono internals using 3 quarters of the total execution time?

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• How to save objects using Multi-Threading in Core Data?

  - by Konstantin

  I'm getting some data from the web service and saving it in the core data. This workflow looks like this: get xml feed go over every item in that feed, create a new ManagedObject for every feed item download some big binary data for every item and save it into ManagedObject call [managedObjectContext save:] Now, the problem is of course the performance - everything runs on the main thread. I'd like to re-factor as much as possible to another thread, but I'm not sure where I should start. Is it OK to put everything (1-4) to the separate thread?

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• C++ iostream not setting eof bit even if gcount returns 0

  - by raph.amiard

  Hi I'm developping an application under windows, and i'm using fstreams to read and write to the file. I'm writing with fstream opened like this : fs.open(this->filename.c_str(), std::ios::in|std::ios::out|std::ios::binary); and writing with this command fs.write(reinterpret_cast<char*>(&e.element), sizeof(T)); closing the file after each write with fs.close() Reading with ifstream opened like this : is.open(filename, std::ios::in); and reading with this command : is.read(reinterpret_cast<char*>(&e.element), sizeof(T)); The write is going fine. However, i read in a loop this way : while(!is.eof()) { is.read(reinterpret_cast<char*>(&e.element), sizeof(T)); } and the program keeps reading, even though the end of file should be reached. istellg pos is 0, and gcount is equal to 0 too, but the fail bit and eof bit are both ok. I'm running crazy over this, need some help ...

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• Posting an image and textual based data to a wcf service

  - by James Hay

  I have a requirement to write a web service that allows me to post an image to a server along with some additional information about that image. I'm completely new to developing web services (normally client side dev) so I'm a little stumped as to what I need to look into and try. How do you post binary data and plain text into a servic? What RequestFormat should I use? It looks like my options are xml or json. Can I use either of these? Bit of a waffly question but I just need some direction rather than a solution as I can't seem to find much online.

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• Are memcached entries saved by the Danga client compatible with the Spy client?

  - by jigjig

  After saving a String value into memcached using the Danga client, I attempted to get the entry using the Spy client. The two String values are not the same. The Danga client retrieves a string with an additional empty char prepended to the string, therefore violating the equality condition. Danga: t,e,s,t,s,t,r,i,n,g Spy: ,t,e,s,t,s,t,r,i,n,g I also attempted to save a serialized Map using the Danga client and get the Map using the Spy client. The Spy client is able to only get a String form of the Map. The string contains binary values, as below: sr

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• Remove then Query fails in JPA (deleted entity passed to persist)

  - by nag

  I have two entitys MobeeCustomer and CustomerRegion i want to remove the object from CustomerRegion first Im put join Coloumn in CustomerRegion is null then Remove the Object from the entityManager but Iam getting Exception MobeeCustomer: public class MobeeCustomer implements Serialization{ private Long id; private String custName; private String Address; private String phoneNo; private Set<CustomerRegion> customerRegion = new HashSet<CustomerRegion>(0); @OneToMany(cascade = { CascadeType.PERSIST, CascadeType.REMOVE }, fetch = FetchType.LAZY, mappedBy = "mobeeCustomer") public Set<CustomerRegion> getCustomerRegion() { return CustomerRegion; } public void setCustomerRegion(Set<CustomerRegion> customerRegion) { CustomerRegion = customerRegion; } } CustomerRegion public class CustomerRegion implements Serializable{ private Long id; private String custName; private String description; private String createdBy; private Date createdOn; private String updatedBy; private Date updatedOn; private MobeeCustomer mobeeCustomer; @ManyToOne(fetch = FetchType.LAZY) @JoinColumn(name = "MOBEE_CUSTOMER") public MobeeCustomer getMobeeCustomer() { return mobeeCustomer; } public void setMobeeCustomer(MobeeCustomer mobeeCustomer) { this.mobeeCustomer = mobeeCustomer; } } sample code: for (CustomerRegion region : deletedRegionList) { region.setMobeeCustomer(null); getEntityManager().remove(region); } StackTrace: please suggest me how to remove the CustomerRegion Object I am getting Exception javax.persistence.EntityNotFoundException: deleted entity passed to persist: [com.manam.mobee.persist.entity.CustomerRegion#<null>] 15:46:34,614 ERROR [STDERR] at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:613) 15:46:34,614 ERROR [STDERR] at org.hibernate.ejb.AbstractEntityManagerImpl.flush(AbstractEntityManagerImpl.java:299) 15:46:34,614 ERROR [STDERR] at org.jboss.seam.persistence.EntityManagerProxy.flush(EntityManagerProxy.java:92) 15:46:34,614 ERROR [STDERR] at org.jboss.seam.framework.EntityHome.update(EntityHome.java:64)

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• NHibernate How to specify custom sql type only in production

  - by Davide Orazio Montersino

  I am saving binary files into a Sql Server 2005 Db using Fluent NHibernate. However, I am using SQLite to run my (pseudo) Unit Tests. I need to use a custom Sql type for Ms Sql, but it would throw an error on SqlLite. What strategies can I use? This is the Map file: public class BinaryFile { public BinaryFile() { m.Map(x => x.BinaryData);//.CustomSqlType("varbinary(MAX)"); m.Map(x => x.ContentType); m.Map(x => x.FileName); m.Map(x => x.FileSize); } }

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• #define vs enum in an embedded environment (How do they compile?)

  - by Alexander Kondratskiy

  This question has been done to death, and I would agree that enums are the way to go. However, I am curious as to how enums compile in the final code- #defines are just string replacements, but do enums add anything to the compiled binary? Or are they both equivalent at that stage. When writing firmware and memory is very limited, is there any advantage, no matter how small, to using #defines? Thanks! EDIT: As requested by the comment below, by embedded, I mean a digital camera. Thanks for the answers! I am all for enums!

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• how to use random bits to simulate a fair 26-sided die?

  - by Michael Levin

  How do I use a random number generator that gives bits (0 or 1) to simulate a fair 26-sided die? I want to use a bitstream to pick letters of the English alphabet such that the odds of any one letter coming up is the same as the odds of any other letter (I know real words aren't like that and have specific frequency distributions for each letter but it doesn't matter here). What's the best way to use binary 0/1 decisions to pick letters fairly from the set A-Z? I can think of a few ways to map bits onto letters but it's not obvious to me that they won't be biased. Is there a known good way?

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• visual c# 2008 database application examples

  - by Omar

  hi, i just have a few weeks programming with vc# (2008) and i'm trying to build an application (winforms) and i have the following problem... i need my application to work with and without connection to the mssql database, this sounds like piece of cake for our friend DataSet right? i can persist the data as XML or binary until i can reach the database and the DataSet will magically sync; all without bothering the user. The problem is... the few books i have read just mention that logic like a fairy tale but dont give any practical example of how to do it, can you point me to one example/demo/whatever i can read or download of an application with (equal or) similar logic?

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• BlazeDS rejected connection from some IP address

  - by Shamal Karunarathne

  Hi, I'm using the BlazeDS binary version with Apache tomcat 6.0. And it seems there's a developer mode active and it only allows 3 IPs to connect to the application (Server). This is what the log says: [BlazeDS]MessageBroker '__default__' rejected connection from address 'xxx.xxx.xx.x'; Developer mode addresses already in use: xxx.x.xxx.xx, xxx.xxx.xxx.xxx, xx.xxx.xxx.xx (IP addresses are masked with 'x' for privacy) I have not added any special configuration to make developer mode active. I couldn't find any resources related to this scenario either. Please help. Thanks in Advance.

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• ASMX schema varies when using WCF Service

  - by Lijo

  Hi, I have a client (created using ASMX "Add Web Reference"). The service is WCF. The signature of the methods varies for the client and the Service. I get some unwanted parameteres to the method. Note: I have used IsRequired = true for DataMember. Service: [OperationContract] int GetInt(); Client: proxy.GetInt(out requiredResult, out resultBool); Could you please help me to make the schame non-varying in both WCF clinet and non-WCF cliet? Do we have any best practices for that? using System.ServiceModel; using System.Runtime.Serialization; namespace SimpleLibraryService { [ServiceContract(Namespace = "http://Lijo.Samples")] public interface IElementaryService { [OperationContract] int GetInt(); [OperationContract] int SecondTestInt(); } public class NameDecorator : IElementaryService { [DataMember(IsRequired=true)] int resultIntVal = 1; int firstVal = 1; public int GetInt() { return firstVal; } public int SecondTestInt() { return resultIntVal; } } } Binding = "basicHttpBinding" using NonWCFClient.WebServiceTEST; namespace NonWCFClient { class Program { static void Main(string[] args) { NonWCFClient.WebServiceTEST.NameDecorator proxy = new NameDecorator(); int requiredResult =0; bool resultBool = false; proxy.GetInt(out requiredResult, out resultBool); Console.WriteLine("GetInt___"+requiredResult.ToString() +"__" + resultBool.ToString()); int secondResult =0; bool secondBool = false; proxy.SecondTestInt(out secondResult, out secondBool); Console.WriteLine("SecondTestInt___" + secondResult.ToString() + "__" + secondBool.ToString()); Console.ReadLine(); } } } Please help.. Thanks Lijo

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• WCF RIA Services v1.0 Timeouts

  - by Dan Wray

  I have a RIA service methods which return quite a large amount of (binary) data to my silverlight application. The methods themselves (database access etc) complete quickly, but since I upgraded to v1.0 from the RC2 I've been experiencing timeouts, even when I limit the data returned to the smallest objects. Debug shows the method returning, then 20-30 seconds later the silverlight "method complete" event will fire. There is not enough data to cause that much lag. Could anyone suggest why this might be? I've been unable to find any breaking changes documentation specific to the RC2 = 1.0 upgrade. Trying to eliminate any other possible causes also, but this is literally a case of worked before the install, doesn't work now! (also upgraded silverlight 4 tools for vs).

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• In App Purchase Problem

  - by Chris

  hi , please help me , i am getting product count 0 in response.product. i have followed all the steps of in app purchase in documentation . 1.Provisioning profile and i allowed in app purchase. 2.Dummy app binary uploaded to itunes and rejected that by myself. 3.Setup 2 products in itunes in app purchase and app identifier was selected. All the things seems fine but i am getting product count 0. Please let me know how can i solve this issue . Thanks

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