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• Sharing a custom datasource between Winforms and Webforms

  - by Earlz

  Hello, I'd like to create a custom datasource that is shared between a Winforms and Webforms project. This functions as a middle layer for a reporting tool(DevExpress Reporting). The Webforms project is a designer for these reports. So we want for the reports to be capable of going to the server to get data and such. So our datasource would abstract away all the communication overhead. Then, for consistency, the datasource would also run on the server for reporting, except for their would be no communication. What would be the best course of action? There doesn't seem to be such a thing as a DataSource in Winforms. Is DataSource not the thing I'm looking for? Edit: After some research, it appears that IDataAdapter may be good for my purpose. Any opinion on that?

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• Image 8-connectivity without excessive branching?

  - by shoosh

  I'm writing a low level image processing algorithm which needs to do alot of 8-connectivity checks for pixels. For every pixel I often need to check the pixels above it, below it and on its sides and diagonals. On the edges of the image there are special cases where there are only 5 or 3 neighbors instead of 8 neighbors for a pixels. The naive way to do it is for every access to check if the coordinates are in the right range and if not, return some default value. I'm looking for a way to avoid all these checks since they introduce a large overhead to the algorithm. Are there any tricks to avoid it altogether?

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• Running Awk command on a cluster

  - by alex

  How do you execute a Unix shell command (awk script, a pipe etc) on a cluster in parallel (step 1) and collect the results back to a central node (step 2) Hadoop seems to be a huge overkill with its 600k LOC and its performance is terrible (takes minutes just to initialize the job) i don't need shared memory, or - something like MPI/openMP as i dont need to synchronize or share anything, don't need a distributed VM or anything as complex Google's SawZall seems to work only with Google proprietary MapReduce API some distributed shell packages i found failed to compile, but there must be a simple way to run a data-centric batch job on a cluster, something as close as possible to native OS, may be using unix RPC calls i liked rsync simplicity but it seem to update remote notes sequentially, and you cant use it for executing scripts as afar as i know switching to Plan 9 or some other network oriented OS looks like another overkill i'm looking for a simple, distributed way to run awk scripts or similar - as close as possible to data with a minimal initialization overhead, in a nothing-shared, nothing-synchronized fashion Thanks Alex

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• Calculation of charged traffic in GPRS network

  - by TyBoer

  I am working with a distributed application communicating over GPRS. I use UDP packets to send business data and ICMP pings to verify connectivity. And now I have a problem with calculating a traffic for which I will be charged by the provider. I have to consider following factors: UDP payload: that is obvious. UDP overhead: UDP header + IP header = 8 + 20 bytes. ICMP echo request without data: IP header + ICMP payload = 28 bytes. ICMP echo reply: as in 3. Above means that for evey data packet I am charged for payload + 28 bytes and for every ping 56 bytes. Am I right or I am missing/misunderstanding something?

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• How to modularize a b2b webservice transformation application

  - by hstoerr

  How would you modularize a large application that has some incoming (SOAP) webservices, some outgoing webservices, transformations between them and internal formats, internal logging services, accesses external archiving webservices, delays stuff and works on this asynchronously and so forth? One way is to split the functionality into a collection of WAR, deploy all of them on one application server and have them communicate with internal webservices. This has some overhead, especially if the messages are large, and you might run into performance problems due to thread count restrictions and so forth. Another way would be to put everything into a giant WAR, such that you can communicate directly. Not exactly modularization. What would you do?

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• Python thread pool similar to the multiprocessing Pool?

  - by Martin

  Is there a Pool class for worker threads, similar to the multiprocessing module's Pool class? I like for example the easy way to parallelize a map function def long_running_func(p): c_func_no_gil(p) p = multiprocessing.Pool(4) xs = p.map(long_running_func, range(100)) however I would like to do it without the overhead of creating new processes. I know about the GIL. However, in my usecase, the function will be an IO-bound C function for which the python wrapper will release the GIL before the actual function call. Do I have to write my own threading pool?

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• Projecting a targetting ring using direct3d

  - by JohnB

  I'm trying to draw a "targetting ring" on the ground below a "unit" in a hobby 3d game I'm working on. Basically I want to project a bright red patterned ring onto the ground terrain below the unit. The only approach I can think of is this - Draw the world once as normal Draw the world a second time but in my vertex shader I have the world x,y,z coordinates of the vertex and I can pass in the coordinates of the highlighted unit - so I can calculate what the u,v coordinates in my project texture should be at that point in the world for that vertex. I'd then use the pixel shader to pick pixels from the target ring texture and blend them into the previously drawn world. I believe that should be easy, and should work but it involves me drawing the whole visible world twice as it's hard to determine exactly which polygons the targetting ring might fall onto. It seems a big overhead to draw the whole world twice, once for the normal lit textured ground, and then again just to draw the targetting ring. Is there a better approach that I'm missing?

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• Computer Vision application(+web interface) for face detection and recognition from database

  - by Kush

  My project is a computer vision java application which should implement the following : A web interface through which the form entry+images(for example a student data) will be stored into a database(Mysql) & images into directory common to my java application. Then the data & images can be retrieved from my java Gui application and I can perform the following operations of image processing through OpenCV. Actually,I want to run the face detection on images retrieved and discard the false entries(no proper face). Also the application user/admin can search an image based on text search(By Id) or By another reference image using face recognition. I am well familiar with Java but the problem is that I need a guidance on how to organise it in a stepwise manner(links appreciated).OpenCv,Php and mySql are really messy.I know doing the openCV stuff within java is real overhead but i really want to do it.But If there is any suggestion to do it elseway please guide me.So any kind of help is a ray of hope for me. Thanks.

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• Learning Ruby on Rails

  - by Ethan Gunderson

  As it stands now I'm a Java and C# developer, but the more and more I look at Ruby on Rails, the more I really want to learn it. What have you found to be the best route to learn RoR? Would it be easier to develop on Windows, or should I just run a virtual machine with linux? Is there an ide that can match the robustness of Visual Studio? Any programs to develop that give a good overhead of what to do? Any good books? Seriously, any tips/tricks/rants would be awesome.

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• Is there a Java equivalent to libevent?

  - by JoelPM

  I've written a high-throughput server that handles each request in its own thread. For requests coming in it is occasionally necessary to do RPCs to one or more back-ends. These back-end RPCs are handled by a separate queue and thread-pool, which provides some bounding on the number of threads created and the maximum number of connections to the back-end (it does some caching to reuse clients and save the overhead of constantly creating connections). Having done all this, though, I'm beginning to think an event-based architecture would be more efficient. In searching around I haven't found any equivalents to libevent for Java, but maybe I'm not looking in the right place? Mina-statemachine from Apache was the closest thing I found, but it looks more verbose than I need and there's no real release available. Any suggestions?

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• Representing Sparse Data in PostgreSQL

  - by Chris S

  What's the best way to represent a sparse data matrix in PostgreSQL? The two obvious methods I see are: Store data in a single a table with a separate column for every conceivable feature (potentially millions), but with a default value of NULL for unused features. This is conceptually very simple, but I know that with most RDMS implementations, that this is typically very inefficient, since the NULL values ususually takes up some space. However, I read an article (can't find its link unfortunately) that claimed PG doesn't take up data for NULL values, making it better suited for storing sparse data. Create separate "row" and "column" tables, as well as an intermediate table to link them and store the value for the column at that row. I believe this is the more traditional RDMS solution, but there's more complexity and overhead associated with it. I also found PostgreDynamic, which claims to better support sparse data, but I don't want to switch my entire database server to a PG fork just for this feature. Are there any other solutions? Which one should I use?

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• Out of Memory When Loading Java Entities

  - by Hugh Buchanan

  I have a terrible problem that hopefully has a very simple answer. I am running out of memory when I perform a basic If I have code like this: MyEntity myEntity; for (Object id: someIdList) { myEntity = find(id); // do something basic with myEntity } And the find() method is a standard EntityManager related method: public MyEntity find(Object id) { return em.find(mycorp.ejb.entity.MyEntity.class, id); } This code worked a couple of weeks ago, and works fine if there are fewer items in the database. The resulting error I am facing is: java.lang.OutOfMemoryError: GC overhead limit exceeded The exception is coming from oracle toplink calling some oracle jdbc methods. The loop exists because an EJBQL such as "select object(o) from MyEntity as o" will overload the application server when there are lots of records.

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• Why is it preferable to call a static method statically from within an instance of the method's clas

  - by javanix

  If I create an instance of a class in Java, why is it preferable to call a static method of that same class statically, rather than using this.method()? I get a warning from Eclipse when I try to call static method staticMethod() from within the custom class's constructor via this.staticMethod(). public MyClass() { this.staticMethod(); } vs public MyClass() { MyClass.staticMethod(); } Can anyone explain why this is a bad thing to do? It seems to me like the compiler should already have allocated an instance of the object, so statically allocating memory would be unneeded overhead.

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• Check if BigDecimal is integer value

  - by Adamski

  Can anyone recommend an efficient way of determining whether a BigDecimal is an integer value in the mathematical sense? At present I have the following code: private boolean isIntegerValue(BigDecimal bd) { boolean ret; try { bd.toBigIntegerExact(); ret = true; } catch (ArithmeticException ex) { ret = false; } return ret; } ... but would like to avoid the object creation overhead if necessary. Previously I was using bd.longValueExact() which would avoid creating an object if the BigDecimal was using its compact representation internally, but obviously would fail if the value was too big to fit into a long. Any help appreciated.

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• Advantage of using a static member function instead of an equivalent non-static member function?

  - by jonathanasdf

  I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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• Is Lazy Loading required for nHibernate?

  - by johnny

  It took me a long time but I finally got nHibernate's Hello World to work. It worked after I did "lazy loading." Honestly, I couldn't tell you why it all worked, but it did and now I am reading you don't need lazy loading. Is there a hello world that anyone has that is bare bones making nHibernate work? Do you have to have lazy loading? I ask because I would like to use nHibernate but I need to understand how things are working. Thank you. Do you know of a hello world that doesn't have so much overhead? Is it better to use lazy loading? EDIT: I am using asp.net 3.5. Web Application Project.

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• When to use Spring Integration vs. Camel?

  - by ngeek

  As a seasoned Spring user I was assuming that Spring Integration would make the most sense in a recent project requiring some (JMS) messaging capabilities (more details). After some days working with Spring Integration it still feels like a lot of configuration overhead given the amount of channels you have to configure to bring some request-response (listening on different JMS queues) communications in place. Therefore I was looking for some background information how Camel is different from Spring Integration, but it seems like information out there are pretty spare, I found: http://java.dzone.com/articles/spring-integration-and-apache (Very neutral comparison between implementing a real-world integration scenario in Spring Integration vs. Camel, from December 2009) http://hillert.blogspot.com/2009/10/apache-camel-alternatives.html (Comparing Camel with other solutions, October 2009) http://raibledesigns.com/rd/entry/taking_apache_camel_for_a (Matt Raible, October 2008) Question is: what experiences did you make on using the one stack over the other? In which scenarios would you recommend Camel were Spring Integration lacks support? Where do you see pros and cons of each? Any advise from real-world projects are highly appreciated.

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• Converting delimited string to multiple values in mysql

  - by epo

  I have a mysql legacy table which contains an client identifier and a list of items, the latter as a comma-delimited string. E.g. "xyz001", "foo,bar,baz". This is legacy stuff and the user insists on being able to edit a comma delimited string. They now have a requirement for a report table with the above broken into separate rows, e.g. "xyz001", "foo" "xyz001", "bar" "xyz001", "baz" Breaking the string into substrings is easily doable and I have written a procedure to do this by creating a separate table, but that requires triggers to deal with deletes, updates and inserts. This query is required rarely (say once a month) but has to be absolutely up to date when it is run, so e.g. the overhead of triggers is not warranted and scheduled tasks to create the table might not be timely enough. Is there any way to write a function to return a table or a set so that I can join the identifier with the individual items on demand?

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• Is it possible to build a JPA entity by extending a POJO?

  - by Freiheit

  Lets say I have the following POJO: public class MyThing { private int myNumber; private String myData; //assume getter/setter methods } Is it now possible to extend this POJO as a JPA entity? @Entity @Table(name = "my_thing") public class MyThingEntity extends MyThing implements Serializable { @Column(name = "my_number") //????????? @Column(name = "my_data") //???????? } I want to keep the POJO separate from the JPA entity. The POJO lives in a different project and is often used without a persistence layer, my project wants to persist it in a database and do so without the overhead of mapping from a POJO to an entity and back. I understand that JPA entities are POJOs, but in order to use it I would have to include a library that implements javax.persistence and the other projects using the same base object have no use for a persistence layer. Is this possible? Is this a good idea?

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• How to sort in-place using the merge sort algorithm?

  - by eSKay

  I know the question is too open. All I want is someone to tell me how to convert a normal merge sort into an in-place merge sort (or a merge sort with constant extra space overhead). All I can find (on the net) is pages saying "it is too complex" or "out of scope of this text". "The only known ways to merge in-place (without any extra space) are too complex to be reduced to practical program." (from here) Even if it is too complex, can somebody outline the basic concept of how to make the merge sort in-place?

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• How do I use Zend Cache on this particular problem

  - by davykiash

  I have an action that renders two different view scripts based on whether the user is logged in or not. class IndexController extends Zend_Controller_Action { .... public function indexAction() { $auth = Zend_Auth::getInstance(); if($auth->hasIdentity()) { $this->render('indexregistered'); return; } else { $this->render('indexpublic'); return; } } .... } I have seen quite some useful examples on how to use the Zend Cache and they seem to be based on the fact that the action renders one particular script. What am really looking at is the best approach to cache the the indexpublic script does get quite some hits and I would live to avoid the Zend MVC overhead if possible.

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• IIS7 Modules - managed or native?

  - by Simon Linder

  Hi all, as the old ISAPI filters are going to die sooner or later, I want to rewrite an old ISAPI filter that was used in IIS 6 into a module for use in IIS 7. The module will be used globally, meaning it will be used within each site, on a Windows Server 2008 R2 with IIS 7.5 installed, that will host several thousand web sites and managing about 50 application pools. My question now is if I should write that module in managed or unmanaged code? One of my concerns regarding managed code is the massive memory consumption due to the .NET framework overhead. I don't know how this would effect the server's performance. I already wrote modules in managed as well as in unmanaged code. So this is not the bothering my decision. But I would prefer to write the module in C# if there are no huge drawbacks. Any suggestions about that issue?

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• How to stop .Net HttpWebRequest.GetResponse() raising an exception

  - by James

  Surely, surely, surely there is a way to configure the .Net HttpWebRequest object so that it does not raise an exception when HttpWebRequest.GetResponse() is called and any 300 or 400 status codes are returned? Jon Skeet does not think so, so I almost dare not even ask, but I find it hard to believe there is no way around this. 300 and 400 response codes are valid responses in certain circumstances. Why would we be always forced to incur the overhead of an exception? Perhaps there is some obscure configuration setting that evaded Jon Skeet? Perhaps there is a completely different type of request object that can be used that does not have this behavior? (and yes, I know you can just catch the exception and get the response from that, but I would like to find a way not to have to). Thanks for any help

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• Javascript crash / Ajax in IE after 5 times

  - by snarebold

  Hi Please give a look at this site. maimei.ch After 5 times opening a new site via ajax (fancybox) it crashes in IE? One little thing is that i load a whole asp.net site via ajax in the new window. so viewstate and other overhead is there twice after. could this be the problem? if yes, why just after 5 times?. is it possible to call just the content of an specific element via ajax? may be just the innerhtml of the body element of the called site? Thank you and best regards

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• Packaging one or two plugins as a standalone RCP application?

  - by Martin Cowie

  I have a handful of Eclipse plugins that I maintain. They are proving useful enough that non Eclipse users have asked for them without the overhead of a full eclipse install. I am certain this is possible, but uncertain how to make this possible. My attempts at creating a standalone RCP app and then including my plugins as dependencies have given me mixed results. More specifically, my perspective tries to instantiate a view from a plugin and fails (silently)... public void createInitialLayout(IPageLayout layout) { layout.addStandaloneView( "myPlugin.ID", false, IPageLayout.LEFT, 0.25f, editorArea); } ... but as the same plugin implements a search extension, it does show up in the standard Eclipse search dialog. Are there any resources that hardened Eclipse tars can point me to, that will help overcome this hurdle? M.

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