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• Fastest inline-assembly spinlock

  - by sigvardsen

  I'm writing a multithreaded application in c++, where performance is critical. I need to use a lot of locking while copying small structures between threads, for this I have chosen to use spinlocks. I have done some research and speed testing on this and I found that most implementations are roughly equally fast: Microsofts CRITICAL_SECTION, with SpinCount set to 1000, scores about 140 time units Implementing this algorithm with Microsofts InterlockedCompareExchange scores about 95 time units Ive also tried to use some inline assembly with __asm {} using something like this code and it scores about 70 time units, but I am not sure that a proper memory barrier has been created. Edit: The times given here are the time it takes for 2 threads to lock and unlock the spinlock 1,000,000 times. I know this isn't a lot of difference but as a spinlock is a heavily used object, one would think that programmers would have agreed on the fastest possible way to make a spinlock. Googling it leads to many different approaches however. I would think this aforementioned method would be the fastest if implemented using inline assembly and using the instruction CMPXCHG8B instead of comparing 32bit registers. Furthermore memory barriers must be taken into account, this could be done by LOCK CMPXHG8B (I think?), which guarantees "exclusive rights" to the shared memory between cores. At last [some suggests] that for busy waits should be accompanied by NOP:REP that would enable Hyper-threading processors to switch to another thread, but I am not sure whether this is true or not? From my performance-test of different spinlocks, it is seen that there is not much difference, but for purely academic purpose I would like to know which one is fastest. However as I have extremely limited experience in the assembly-language and with memory barriers, I would be happy if someone could write the assembly code for the last example I provided with LOCK CMPXCHG8B and proper memory barriers in the following template: __asm { spin_lock: ;locking code. spin_unlock: ;unlocking code. }

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• Can this auto-stretcing scenario be realized undex XHTML/CSS?

  - by Vilx-

  I want two horizontal areas in my webpage. The first one is the menu. It's on the top. Unfortunately I don't know its size, and it might change in response to user actions. Below the menu is the main area which should stretch at least as far as the bottom of the window (if there is little content) or beyond (if there is a lot of content. To illustrate with ASCII art: +----------------------------------------------------+ | This area resizes vertically depending on contents | +----------------------------------------------------+ | This area stretches to the bottom of the window, | | but can be even larger if necessary. Note: this | | should be a separate area because it will contain | | children with height:100% as well. | | | +----------------------------------------------------+ Can this be done? Can it be done with Javascript? Added: To put things in perspective and avoid confusion, think of it this way: the top menu is generated by myself, but the bottom area is an IFrame which I want to fill the rest of the page. This is what it eventually comes down to anyway in my case.

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• how to return a list using SwingWorker

  - by Ender

  I have an assignment where i have to create an Image Gallery which uses a SwingWorker to load the images froma a file, once the image is load you can flip threw the image and have a slideshow play. I am having trouble getting the list of loaded images using SwingWorker. This is what happens in the background it just publishes the results to a TextArea // In a thread @Override public List<Image> doInBackground() { List<Image> images = new ArrayList<Image>(); for (File filename : filenames) { try { //File file = new File(filename); System.out.println("Attempting to add: " + filename.getAbsolutePath()); images.add(ImageIO.read(filename)); publish("Loaded " + filename); System.out.println("Added file" + filename.getAbsolutePath()); } catch (IOException ioe) { publish("Error loading " + filename); } } return images; } } when it is done I just insert the images in a List<Image> and that is all it does. // In the EDT @Override protected void done() { try { for (Image image : get()) { list.add(image); } } catch (Exception e) { } } Also I created an method that returns the list called getImages() what I need to get is the list from getImages() but doesn't seam to work when I call execute() for example MySwingWorkerClass swingworker = new MySwingWorkerClass(log,list,filenames); swingworker.execute(); imageList = swingworker.getImage() Once it reaches the imageList it doesn't return anything the only way I was able to get the list was when i used the run() instead of the execute() is there another way to get the list or is the run() method the only way?. or perhaps i am not understanding the Swing Worker Class.

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• Multiple Inheritence with same Base Classes in Python

  - by Jordan Reiter

  I'm trying to wrap my head around multiple inheritance in python. Suppose I have the following base class: class Structure(object): def build(self, *args): print "I am building a structure!" self.components = args And let's say I have two classes that inherit from it: class House(Structure): def build(self, *args): print "I am building a house!" super(House, self).build(*args) class School(Structure): def build(self, type="Elementary", *args): print "I am building a school!" super(School, self).build(*args) Finally, a create a class that uses multiple inheritance: class SchoolHouse(School, House): def build(self, *args): print "I am building a schoolhouse!" super(School, self).build(*args) Then, I create a SchoolHouse object and run build on it: >>> sh = SchoolHouse() >>> sh.build("roof", "walls") I am building a schoolhouse! I am building a house! I am building a structure! So I'm wondering -- what happened to the School class? Is there any way to get Python to run both somehow? I'm wondering specifically because there are a fair number of Django packages out there that provide custom Managers for models. But there doesn't appear to be a way to combine them without writing one or the other of the Managers as inheriting from the other one. It'd be nice to just import both and use both somehow, but looks like it can't be done? Also I guess it'd just help to be pointed to a good primer on multiple inheritance in Python. I have done some work with Mixins before and really enjoy using them. I guess I just wonder if there is any elegant way to combine functionality from two different classes when they inherit from the same base class.

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• Recommendations for Continuous integration for Mercurial/Kiln + MSBuild + MSTest

  - by TDD

  We have our source code stored in Kiln/Mercurial repositories; we use MSBuild to build our product and we have Unit Tests that utilize MSTest (Visual Studio Unit Tests). What solutions exist to implement a continuous integration machine (i.e. Build machine). The requirements for this are: A build should be kicked of when necessary (i.e. code has changed in the Repositories we care about) Before the actual build, the latest version of the source code must be acquired from the repository we are building from The build must build the entire product The build must build all Unit Tests The build must execute all unit tests A summary of success/failure must be sent out after the build has finished; this must include information about the build itself but also about which Unit Tests failed and which ones succeeded. The summary must contain which changesets were in this build that were not yet in the previous successful (!) build The system must be configurable so that it can build from multiple branches(/Repositories). Ideally, this system would run on a single box (our product isn't that big) without any server components. What solutions are currently available? What are their pros/cons? From the list above, what can be done and what cannot be done? Thanks

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• curl_multi_exec stops if one url is 404, how can I change that?

  - by Rob

  Currently, my cURL multi exec stops if one url it connects to doesn't work, so a few questions: 1: Why does it stop? That doesn't make sense to me. 2: How can I make it continue? EDIT: Here is my code: $SQL = mysql_query("SELECT url FROM shells") ; $mh = curl_multi_init(); $handles = array(); while($resultSet = mysql_fetch_array($SQL)){ //load the urls and send GET data $ch = curl_init($resultSet['url'] . $fullcurl); //Only load it for two seconds (Long enough to send the data) curl_setopt($ch, CURLOPT_TIMEOUT, 5); curl_multi_add_handle($mh, $ch); $handles[] = $ch; } // Create a status variable so we know when exec is done. $running = null; //execute the handles do { // Call exec. This call is non-blocking, meaning it works in the background. curl_multi_exec($mh,$running); // Sleep while it's executing. You could do other work here, if you have any. sleep(2); // Keep going until it's done. } while ($running > 0); // For loop to remove (close) the regular handles. foreach($handles as $ch) { // Remove the current array handle. curl_multi_remove_handle($mh, $ch); } // Close the multi handle curl_multi_close($mh);

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• Bootstarap: want to trigger some costum events on layout change

  - by DS_web_developer

  So, there are some events in my app that changes layout on my page (re-position of the elements)... mostly is done by bootstrap collapsing and fading (tabs, collapsibles, accordions)... I would like to fire an event whenever a change is about to happen and another when the change is done.. right now I came out with something like that $('.collapse').on("shown hidden", function(){ jQuery(myAPP).trigger("layoutchanged"); }); $('.collapse').on("show hide", function(){ jQuery(myAPP).trigger("layoutchanging"); }); and then... jQuery(myAPP).on("layoutchanging", function(e){ log("Start changing"); }); jQuery(myAPP).on("layoutchanged", function(e){ log("Layout changed"); }); it works for collapse and accordions OK. but on tabs, where the markup is like this: <ul class="nav nav-tabs can_deactivate"> <li><a href="#tab_1" data-toggle="tab">Open Tab 1</a></li> <li><a href="#tab_2" data-toggle="tab">Open Tab 2</a></li> </ul> <div class="tab-content"> <div class="tab-pane fade" id="tab_1"> Lorem ipsum </div> <div class="tab-pane fade" id="tab_2"> Lorem ipsum </div> </div> Works only on show, but not on hide... what can I do? JS FIDDLE: http://jsfiddle.net/KL7Af/

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• How to best launch C++ application from web page

  - by JB

  I guess there are two parts to this question, one technical and one best practice for security and doing things "right". I'm working on a little game using C++ / directx but I would like to be able to launch it from a web page by someone clicking on a link on that page. Ideally I would like the first time they clicked for it to launch an installer downloads and installs the game on their machine, and then the next time to launch an application which updates the game from a web site if it's old and then launches it. I have no problems with the expected security popups and questions the first time it runs. I want people to be certain what they are installing and understand what they are doing. But it would be nice if once it is installed they could run it with the minimum of fuss. My question then is what technologies I could use to do this? I'm thinking that it would need a browser plugin and an activex control so that first time you'd install that, and subsequently the control/plugin would be able to launch the game. I'm not sure that under newer browser secuity models that a plugin would have the permissions to be able to run an installer though or silently invoke applications on the client machine even if they are already installed. Is there a more sensible way to achive what I want to achieve? And I'm worried about the security aspects too. I want this to be convenient for users but I of course want to do it "right". I know this can be done as I've seen several mmorpg type games that launch in this way from the browser now but it's not entirely clear to me how they've done it.

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• Servlet send image from server and save in client

  - by sangi

  Hi, I'm new and just developing on J2EE. I am modifying an existing application (an OpenSource project). I need to save an image on a client sent by the server, but I do not know how. This activity must be done in a transparent manner without affecting the existing operation of the application. From the tests done I get this error: java.lang.IllegalStateException: getWriter () has Already Been Called for this response. How should carry out this task, according to your own opinion? How do I save on the client, locally, the image? Update: Thanks for the answers. My problem is that: the image is generated on the server, but not for direct client request (there is no link to click on web page), the picture is composed using other services on the Internet. reconstruct the image on the server. This image must be sent to the client to be saved locally. so I'd like it to appear a window where you assign the destination image plus I'd like the rest of the application were not affected by this activity. The application is yet on production. Thank you very much for your response.

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• What if a large number of objects are passed to my SwingWorker.process() method?

  - by Trejkaz

  I just found an interesting situation. Suppose you have some SwingWorker (I've made this one vaguely reminiscent of my own): public class AddressTreeBuildingWorker extends SwingWorker<Void, NodePair> { private DefaultTreeModel model; public AddressTreeBuildingWorker(DefaultTreeModel model) { } @Override protected Void doInBackground() { // Omitted; performs variable processing to build a tree of address nodes. } @Override protected void process(List<NodePair> chunks) { for (NodePair pair : chunks) { // Actually the real thing inserts in order. model.insertNodeInto(parent, child, parent.getChildCount()); } } private static class NodePair { private final DefaultMutableTreeNode parent; private final DefaultMutableTreeNode child; private NodePair(DefaultMutableTreeNode parent, DefaultMutableTreeNode child) { this.parent = parent; this.child = child; } } } If the work done in the background is significant then things work well - process() is called with relatively small lists of objects and everything is happy. Problem is, if the work done in the background is suddenly insignificant for whatever reason, process() receives a huge list of objects (I have seen 1,000,000, for instance) and by the time you process each object, you have spent 20 seconds on the Event Dispatch Thread, exactly what SwingWorker was designed to avoid. In case it isn't clear, both of these occur on the same SwingWorker class for me - it depends on the input data, and the type of processing the caller wanted. Is there a proper way to handle this? Obviously I can intentionally delay or yield the background processing thread so that a smaller number might arrive each time, but this doesn't feel like the right solution to me.

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• VB.NET: Dialog exits when enter pressed?

  - by Camilo Martin

  Hi all; My problem seems to be quite simple, but it's not working the intuitive way. I'm designing a Windows Forms Application, and there is a dialog that should NOT exit when the enter key is pressed, instead it has to validate data first, in case enter was pressed after changing the text of a ComboBox. I've tried by telling it what to do on KeyPress event of the ComboBox if e is the Enter key: Private Sub ComboBoxSizeChoose_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles ComboBoxSizeChoose.KeyPress If e.KeyChar = Convert.ToChar(Keys.Enter) Then Try TamanhoDaNovaFonte = Single.Parse(ComboBoxSizeChoose.Text) Catch ex As Exception Dim Dialogo2 As New Dialog2 Dialog2.ShowDialog() ComboBoxSizeChoose.Text = TamanhoDaNovaFonte End Try End If End Sub But no success so far. When the Enter key is pressed, even with the ComboBox on focus, the whole dialog is closed, returning to the previous form. The validation is NOT done at all, and it has to be done before exiting. In fact, I don't even want to exit on the form's enter KeyPress, the only purpose of the enter key on the whole dialog is to validate the ComboBox (but only when in focus, for the sake of an intuitive UI). I've also tried appending the validation to the KeyPress event of the whole dialog's form, if the key is Enter. NO SUCCESS! It's like my code wasn't there at all. What should I do? (Visual Studio 2008, VB.NET)

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• How to install Zend Framework on Windows

  - by sombe

  "installing Zend Framework is so easy!!!!" yeah right... Ok I'm working with a beginner's book and the ONE thing that is not excessively detailed is the most important part: Installing the darn thing. After browsing the quickstart guide for hours, all it said was: "download Zend [...] add the include directory (bla bla) and YOU'RE DONE!" right, i'm done using Zend. Ok, not really, not yet anyway. I beg of you people, I wanna go to bed, please tell me how (in simple 6th grade detail) to install the framework. I've got the unzipped folder in my htdocs directory, and I placed zf.bat+zf.php in the htdocs root. What's next? thank you so much. EDIT: Thanks guys for all the answers. Unfortunately I haven't been able to work with this or find a good enough resource to explain it to me in plain english. It seems that this framework adheres more so to programmers than to beginners. I've since yesterday read a little on CakePHP and found that it was incredibly easy to install and tune. As oppose to Zend Framework, where I had to dig in my "environment variables", configure "httpd.conf" and almost tie the knot between my computer driver cables to just get it running, CakePHP has already allowed me to put together a nice newbie application. In conclusion, I very much appreciate all of your help. I hope someone else venturing on ZF will be more successful with it. Thanks!

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• Copying a foreign Subversion repository to keep under dependencies

  - by Jonathan Sternberg

  I want to keep dependencies for my project in our own repository, that way we have consistent libraries for the entire team to work with. For example, I want our project to use the Boost libraries. I've seen this done in the past with putting dependencies under a "vendor" or "dependencies" folder. But I still want to be able to update these dependencies. If a new feature appears in a library and we need it, I want to just be able to update that repository within our own repository. I don't want to have to recopy it and put it under version control again. I'd also like for us to have the ability to change dependencies if a small change is needed without stopping us from ever updating the library. I want the ability to do something like 'svn cp', then be able to 'svn merge' in the future. I just tried this with the boost trunk, but I'm not able to get any history using 'svn log' on the copy I made. How do I do this? What is usually done for large projects with dependencies?

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• What shall be the code in xaml which makes a particular image to act as a button?

  - by Abhi

  Dear all I am new to Silverlight. And i have to make a demo application where in designing is done by using Microsoft Expression Blend 2 and developing should be done using Visual Studio(c++). Now i am first trying to become familiar with xaml files. So i was trying to make a simple demo where in i have to create a button and that button should be replace with an png image. In order to do so i tried with the mentioned below example. But i was not able to see anything in the screen. <UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="SilverlightApplication1.Page" Width="640" Height="480"> <Grid x:Name="LayoutRoot" Background="White"> <Button x:Name="LogoutButton" > <Button.Template> <ControlTemplate> <Image Source="SilverlightApplication1\bounce_photo.png" /> </ControlTemplate> </Button.Template> </Button> </Grid> Please let me know where i am wrong and what shall i do to obtain the result. With regards Abhineet Agarwal

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• strange segmentation fault during function return

  - by Kyle

  I am running a program on 2 different machines. On one it works fine without issue. On the other it results in a segmentation fault. Through debugging, I have figured out where the fault occurs, but I can't figure out a logical reason for it to happen. In one function I have the following code: pass_particles(particle_grid, particle_properties, input_data, coll_eros_track, collision_number_part, world, grid_rank_lookup, grid_locations); cout<<"done passing particles"<<endl; The function pass_particles looks like: void pass_particles(map<int,map<int,Particle> > & particle_grid, std::vector<Particle_props> & particle_properties, User_input& input_data, data_tracking & coll_eros_track, vector<int> & collision_number_part, mpi::communicator & world, std::map<int,int> & grid_rank_lookup, map<int,std::vector<double> > & grid_locations) { //cout<<"east-west"<<endl; //east-west exchange (x direction) map<int, vector<Particle> > particles_to_be_sent_east; map<int, vector<Particle> > particles_to_be_sent_west; vector<Particle> particles_received_east; vector<Particle> particles_received_west; int counter_x_sent=0; int counter_x_received=0; for(grid_iter=particle_grid.begin();grid_iter!=particle_grid.end();grid_iter++) { map<int,Particle>::iterator part_iter; for (part_iter=grid_iter->second.begin();part_iter!=grid_iter->second.end();) { if (particle_properties[part_iter->second.global_part_num()].particle_in_box()[grid_iter->first]) { //decide if a particle has left the box...need to consider whether particle was already outside the box if ((part_iter->second.position().x()<(grid_locations[grid_iter->first][0]) && part_iter->second.position().x()>(grid_locations[grid_iter->first-input_data.z_numboxes()][0])) || (input_data.periodic_walls_x() && (grid_iter->first-floor(grid_iter->first/(input_data.xz_numboxes()))*input_data.xz_numboxes()<input_data.z_numboxes()) && (part_iter->second.position().x()>(grid_locations[input_data.total_boxes()-1][0])))) { particles_to_be_sent_west[grid_iter->first].push_back(part_iter->second); particle_properties[particle_grid[grid_iter->first][part_iter->first].global_part_num()].particle_in_box()[grid_iter->first]=false; counter_sent++; counter_x_sent++; } else if ((part_iter->second.position().x()>(grid_locations[grid_iter->first][1]) && part_iter->second.position().x()<(grid_locations[grid_iter->first+input_data.z_numboxes()][1])) || (input_data.periodic_walls_x() && (grid_iter->first-floor(grid_iter->first/(input_data.xz_numboxes()))*input_data.xz_numboxes())>input_data.xz_numboxes()-input_data.z_numboxes()-1) && (part_iter->second.position().x()<(grid_locations[0][1]))) { particles_to_be_sent_east[grid_iter->first].push_back(part_iter->second); particle_properties[particle_grid[grid_iter->first][part_iter->first].global_part_num()].particle_in_box()[grid_iter->first]=false; counter_sent++; counter_x_sent++; } //select particles in overlap areas to send to neighboring cells else if ((part_iter->second.position().x()>(grid_locations[grid_iter->first][0]) && part_iter->second.position().x()<(grid_locations[grid_iter->first][0]+input_data.diam_large()))) { particles_to_be_sent_west[grid_iter->first].push_back(part_iter->second); counter_sent++; counter_x_sent++; } else if ((part_iter->second.position().x()<(grid_locations[grid_iter->first][1]) && part_iter->second.position().x()>(grid_locations[grid_iter->first][1]-input_data.diam_large()))) { particles_to_be_sent_east[grid_iter->first].push_back(part_iter->second); counter_sent++; counter_x_sent++; } ++part_iter; } else if (particles_received_current[grid_iter->first].find(part_iter->first)!=particles_received_current[grid_iter->first].end()) { if ((part_iter->second.position().x()>(grid_locations[grid_iter->first][0]) && part_iter->second.position().x()<(grid_locations[grid_iter->first][0]+input_data.diam_large()))) { particles_to_be_sent_west[grid_iter->first].push_back(part_iter->second); counter_sent++; counter_x_sent++; } else if ((part_iter->second.position().x()<(grid_locations[grid_iter->first][1]) && part_iter->second.position().x()>(grid_locations[grid_iter->first][1]-input_data.diam_large()))) { particles_to_be_sent_east[grid_iter->first].push_back(part_iter->second); counter_sent++; counter_x_sent++; } part_iter++; } else { particle_grid[grid_iter->first].erase(part_iter++); counter_removed++; } } } world.barrier(); mpi::request reqs_x_send[particles_to_be_sent_west.size()+particles_to_be_sent_east.size()]; vector<multimap<int,int> > box_sent_x_info; box_sent_x_info.resize(world.size()); vector<multimap<int,int> > box_received_x_info; box_received_x_info.resize(world.size()); int counter_x_reqs=0; //send particles for(grid_iter_vec=particles_to_be_sent_west.begin();grid_iter_vec!=particles_to_be_sent_west.end();grid_iter_vec++) { if (grid_iter_vec->second.size()!=0) { //send a particle. 50 will be "west" tag if (input_data.periodic_walls_x() && (grid_iter_vec->first-floor(grid_iter_vec->first/(input_data.xz_numboxes()))*input_data.xz_numboxes()<input_data.z_numboxes())) { reqs_x_send[counter_x_reqs++]=world.isend(grid_rank_lookup[grid_iter_vec->first + input_data.z_numboxes()*(input_data.x_numboxes()-1)], grid_iter_vec->first + input_data.z_numboxes()*(input_data.x_numboxes()-1), particles_to_be_sent_west[grid_iter_vec->first]); box_sent_x_info[grid_rank_lookup[grid_iter_vec->first + input_data.z_numboxes()*(input_data.x_numboxes()-1)]].insert(pair<int,int>(world.rank(), grid_iter_vec->first + input_data.z_numboxes()*(input_data.x_numboxes()-1))); } else if (!(grid_iter_vec->first-floor(grid_iter_vec->first/(input_data.xz_numboxes()))*input_data.xz_numboxes()<input_data.z_numboxes())) { reqs_x_send[counter_x_reqs++]=world.isend(grid_rank_lookup[grid_iter_vec->first - input_data.z_numboxes()], grid_iter_vec->first - input_data.z_numboxes(), particles_to_be_sent_west[grid_iter_vec->first]); box_sent_x_info[grid_rank_lookup[grid_iter_vec->first - input_data.z_numboxes()]].insert(pair<int,int>(world.rank(),grid_iter_vec->first - input_data.z_numboxes())); } } } for(grid_iter_vec=particles_to_be_sent_east.begin();grid_iter_vec!=particles_to_be_sent_east.end();grid_iter_vec++) { if (grid_iter_vec->second.size()!=0) { //send a particle. 60 will be "east" tag if (input_data.periodic_walls_x() && (grid_iter_vec->first-floor(grid_iter_vec->first/(input_data.xz_numboxes())*input_data.xz_numboxes())>input_data.xz_numboxes()-input_data.z_numboxes()-1)) { reqs_x_send[counter_x_reqs++]=world.isend(grid_rank_lookup[grid_iter_vec->first - input_data.z_numboxes()*(input_data.x_numboxes()-1)], 2000000000-(grid_iter_vec->first - input_data.z_numboxes()*(input_data.x_numboxes()-1)), particles_to_be_sent_east[grid_iter_vec->first]); box_sent_x_info[grid_rank_lookup[grid_iter_vec->first - input_data.z_numboxes()*(input_data.x_numboxes()-1)]].insert(pair<int,int>(world.rank(),2000000000-(grid_iter_vec->first - input_data.z_numboxes()*(input_data.x_numboxes()-1)))); } else if (!(grid_iter_vec->first-floor(grid_iter_vec->first/(input_data.xz_numboxes())*input_data.xz_numboxes())>input_data.xz_numboxes()-input_data.z_numboxes()-1)) { reqs_x_send[counter_x_reqs++]=world.isend(grid_rank_lookup[grid_iter_vec->first + input_data.z_numboxes()], 2000000000-(grid_iter_vec->first + input_data.z_numboxes()), particles_to_be_sent_east[grid_iter_vec->first]); box_sent_x_info[grid_rank_lookup[grid_iter_vec->first + input_data.z_numboxes()]].insert(pair<int,int>(world.rank(), 2000000000-(grid_iter_vec->first + input_data.z_numboxes()))); } } } counter=0; for (int i=0;i<world.size();i++) { //if (world.rank()!=i) //{ reqs[counter++]=world.isend(i,1000000000,box_sent_x_info[i]); reqs[counter++]=world.irecv(i,1000000000,box_received_x_info[i]); //} } mpi::wait_all(reqs, reqs + world.size()*2); //receive particles //receive west particles for (int j=0;j<world.size();j++) { multimap<int,int>::iterator received_info_iter; for (received_info_iter=box_received_x_info[j].begin();received_info_iter!=box_received_x_info[j].end();received_info_iter++) { //receive the message if (received_info_iter->second<1000000000) { //receive the message world.recv(received_info_iter->first,received_info_iter->second,particles_received_west); //loop through all the received particles and add them to the particle_grid for this processor for (unsigned int i=0;i<particles_received_west.size();i++) { particle_grid[received_info_iter->second].insert(pair<int,Particle>(particles_received_west[i].global_part_num(),particles_received_west[i])); if(particles_received_west[i].position().x()>grid_locations[received_info_iter->second][0] && particles_received_west[i].position().x()<grid_locations[received_info_iter->second][1]) { particle_properties[particles_received_west[i].global_part_num()].particle_in_box()[received_info_iter->second]=true; } counter_received++; counter_x_received++; } } else { //receive the message world.recv(received_info_iter->first,received_info_iter->second,particles_received_east); //loop through all the received particles and add them to the particle_grid for this processor for (unsigned int i=0;i<particles_received_east.size();i++) { particle_grid[2000000000-received_info_iter->second].insert(pair<int,Particle>(particles_received_east[i].global_part_num(),particles_received_east[i])); if(particles_received_east[i].position().x()>grid_locations[2000000000-received_info_iter->second][0] && particles_received_east[i].position().x()<grid_locations[2000000000-received_info_iter->second][1]) { particle_properties[particles_received_east[i].global_part_num()].particle_in_box()[2000000000-received_info_iter->second]=true; } counter_received++; counter_x_received++; } } } } mpi::wait_all(reqs_y_send, reqs_y_send + particles_to_be_sent_bottom.size()+particles_to_be_sent_top.size()); mpi::wait_all(reqs_z_send, reqs_z_send + particles_to_be_sent_south.size()+particles_to_be_sent_north.size()); mpi::wait_all(reqs_x_send, reqs_x_send + particles_to_be_sent_west.size()+particles_to_be_sent_east.size()); cout<<"x sent "<<counter_x_sent<<" and received "<<counter_x_received<<" from rank "<<world.rank()<<endl; cout<<"rank "<<world.rank()<<" sent "<<counter_sent<<" and received "<<counter_received<<" and removed "<<counter_removed<<endl; cout<<"done passing"<<endl; } I only posted some of the code (so ignore the fact that some variables may appear to be undefined, as they are in a portion of the code I didn't post) When I run the code (on the machine in which it fails), I get done passing but not done passing particles I am lost as to what could possibly cause a segmentation fault between the end of the called function and the next line in the calling function and why it would happen on one machine and not another.

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• Aligning music notes using String matching algorithms or Dynamic Programming

  - by Dolphin

  Hi I need to compare 2 sets of musical pieces (i.e. a playing-taken in MIDI format-note details extracted and saved in a database table, against sheet music-taken into XML format). When evaluating playing against sheet music (i.e.note details-pitch, duration, rhythm), note alignment needs to be done - to identify missed/extra/incorrect/swapped notes that from the reference (sheet music) notes. I have like 1800-2500 notes in one piece approx (can even be more-with polyphonic, right now I'm doing for monophonic). So will I have to have all these into an array? Will it be memory overloading or stack overflow? There are string matching algorithms like KMP, Boyce-Moore. But note alignment can also be done through Dynamic Programming. How can I use Dynamic Programming to approach this? What are the available algorithms? Is it about approximate string matching? Which approach is much productive? String matching algos like Boyce-Moore, or dynamic programming? How can I assess which is more effective? Greatly appreciate any insight or suggestions Thanks in advance

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• What are the advantages of using J2EE over ASP.net?

  - by m_oLogin

  We are currently planning to launch a couple of internal web projects in the future. Our company's dev teams are mostly experienced in J2EE and have worked with it for years. Today, we have the choice of launching a couple of our projects on .net. I have checked out a couple of sources on the net, and it seems like the "J2EE vs ASP.net" combat brings out as much discord as the overseen "Apple vs Microsoft" or "Free Eclipse vs Visual Studio"... Nevertheless, I have been somewhat quite impressed with ASP.net's abilities to create great things with huge simplicity (for ex. asp.net ajax's demos). No more tons of xmls to play with, no more tons of frameworks to configure (we usually use the famous combo struts/spring/hibernate)... It just seemed to me that ASP.net had some good advantages over J2EE, but then again, I may speak by ignorance. What I want to know is this : What are the real advantages of using J2EE over ASP.net? Is there anything that cannot be done in ASP.net that can be done in J2EE? Once the frameworks are all in place and configured, is it faster to develop apps in J2EE than it is in .net? Are the applications generally easier to maintain in J2EE than in ASP.net? Is it worth it for some developpers to leave their J2EE knowledge on the side and move on to ASP.net if it does exactly the same thing?

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• Java object graph -> xml when direction of object association needs to be reversed.

  - by Sigmoidal

  An application I have been working on has objects with a relationship similar to below. In the real application both objects are JPA entities. class Underlying{} class Thing { private Underlying underlying; public Underlying getUnderlying() { return underlying; } public void setUnderlying(final Underlying underlying) { this.underlying = underlying; } } There is a requirement in the application to create xml of the form: <template> <underlying> <thing/> <thing/> <thing/> </underlying> </template> So we have a situation where the object graph expresses the relationship between Thing and Underlying in the opposite direction to how it's expressed in the xml. I expect to use JAXB to create the xml but ideally I don't want to have to create a new object hierarchy to reflect the associations in the xml. Is there any way to create xml of the form required from the entities in their current form (through the use of xml annotations or something)? I don't have any experience using JAXB but from the limited research I've done it doesn't seem like it's possible to reverse the direction of association in any straightforward way. Any help/advice would be greatly appreciated. One other option that has been suggested is to use XLST to transform the xml into the correct format. I have done no research on this topic as yet but I'll add to the question when I have some more info. Thanks, Matt.

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• MUD (game) design concept question about timed events.

  - by mudder

  I'm trying my hand at building a MUD (multiplayer interactive-fiction game) I'm in the design/conceptualizing phase and I've run into a problem that I can't come up with a solution for. I'm hoping some more experienced programmers will have some advice. Here's the problem as best I can explain it. When the player decides to perform an action he sends a command to the server. the server then processes the command, determines whether or not the action can be performed, and either does it or responds with a reason as to why it could not be done. One reason that an action might fail is that the player is busy doing something else. For instance, if a player is mid-fight and has just swung a massive broadsword, it might take 3 seconds before he can repeat this action. If the player attempts to swing again to soon, the game will respond indicating that he must wait x seconds before doing that. Now, this I can probably design without much trouble. The problem I'm having is how I can replicate this behavior from AI creatures. All of the events that are being performed by the server ON ITS OWN, aka not as an immediate reaction to something a player has done, will have to be time sensitive. Some evil monster has cast a spell on you but must wait 30 seconds before doing it again... I think I'll probably be adding all these events to some kind of event queue, but how can I make that event queue time sensitive?

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• What is the fastest way to find duplicates in multiple BIG txt files?

  - by user2950750

  I am really in deep water here and I need a lifeline. I have 10 txt files. Each file has up to 100.000.000 lines of data. Each line is simply a number representing something else. Numbers go up to 9 digits. I need to (somehow) scan these 10 files and find the numbers that appear in all 10 files. And here comes the tricky part. I have to do it in less than 2 seconds. I am not a developer, so I need an explanation for dummies. I have done enough research to learn that hash tables and map reduce might be something that I can make use of. But can it really be used to make it this fast, or do I need more advanced solutions? I have also been thinking about cutting up the files into smaller files. To that 1 file with 100.000.000 lines is transformed into 100 files with 1.000.000 lines. But I do not know what is best: 10 files with 100 million lines or 1000 files with 1 million lines? When I try to open the 100 million line file, it takes forever. So I think, maybe, it is just too big to be used. But I don't know if you can write code that will scan it without opening. Speed is the most important factor in this, and I need to know if it can be done as fast as I need it, or if I have to store my data in another way, for example, in a database like mysql or something. Thank you in advance to anybody that can give some good feedback.

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• LinqToSQL: Not possible to update PrimaryKey?

  - by Zuhaib

  I have a simple table (lets call it Table1) that has a NVARCHAR field as the PK. Table1 has no association with any other tables. When I update Table1's PK column using LinqToSQL it fails. If I update other column it succeeds. I could delete this row and insert new one in Table1, but I don't want to. There is a transaction table which has Table1's PK column as a column. When the PK of Table1 is changed I want no effect in the transaction table. But when the row from Table1 is deleted, I want the transaction rows to be deleted. The cascading is done via Trigger. As there is not association between these two tables, if I update the PK column of Table1 using normal SQL, it works and there is no effect on the transaction table as expected. When I delete the row the trigger deletes the rows from transaction table. For this reason I can't delete and then add new row in Table1. So what can be done to successfully update the PrimaryKey of the Table1?

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• real time stock quotes, StreamReader performance optimization

  - by sean717

  I am working on a program that extracts real time quote for 900+ stocks from a website. I use HttpWebRequest to send HTTP request to the site and store the response to a stream and open a stream using the following code: HttpWebResponse response = (HttpWebResponse)request.GetResponse(); Stream stream = response.GetResponseStream (); StreamReader reader = new StreamReader( stream ) the size of the received HTML is large (5000+ lines), so it takes a long time to parse it and extract the price. For 900 files, It takes about 6 mins for parsing and extracting. Which my boss isn't happy with, he told me he'd want the whole process to be done in TWO mins. I've identified the part of the program that takes most of time to finish is parsing and extracting. I've tried to optimize the code to make it faster, the following is what I have now after some optimization: // skip lines at the top for(int i=0;i<1500;++i) reader.ReadLine(); // read the line that contains the price string theLine = reader.ReadLine(); // ... extract the price from the line now it takes about 4 mins to process all the files, there is still a significant gap to what my boss's expecting. So I am wondering, is there other way that I can further speed up the parsing and extracting and have everything done within 2 mins?

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• Cross-domain data access in JavaScript

  - by vit

  We have an ASP.Net application hosted on our network and exposed to a specific client. This client wants to be able to import data from their own server into our application. The data is retrieved with an HTTP request and is CSV formatted. The problem is that they do not want to expose their server to our network and are requesting the import to be done on the client side (all clients are from the same network as their server). So, what needs to be done is: They request an import page from our server The client script on the page issues a request to their server to get CSV formatted data The data is sent back to our application This is not a challenge when both servers are on the same domain: a simple hidden iframe or something similar will do the trick, but here what I'm getting is a cross-domain "access denied" error. They also refuse to change the data format to return JSON or XML formatted data. What I tried and learned so far is: Hidden iframe -- "access denied" XMLHttpRequest -- behaviour depends on the browser security settings: may work, may work while nagging a user with security warnings, or may not work at all Dynamic script tags -- would have worked if they could have returned data in JSON format IE client data binding -- the same "access denied" error Is there anything else I can try before giving up and saying that it will not be possible without exposing their server to our application, changing their data format or changing their browser security settings? (DNS trick is not an option, by the way).

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• Qt application crashing immediately without debugging info. How do I track down the problem?

  - by jjacksonRIAB

  I run an Qt app I've built: ./App Segmentation fault I run it with strace: strace ./App execve("./App", ["./App"], [/* 27 vars */]) = 0 --- SIGSEGV (Segmentation fault) @ 0 (0) --- +++ killed by SIGSEGV +++ Process 868 detached Again, no useful info. I run it with gdb: (gdb) run Starting program: /root/test/App Reading symbols from shared object read from target memory...(no debugging symbols found)...done. Loaded system supplied DSO at 0xffffe000 Program received signal SIGSEGV, Segmentation fault. 0x00000001 in ?? () Again, nothing. I run it with valgrind: ==948== Process terminating with default action of signal 11 (SIGSEGV) ==948== Bad permissions for mapped region at address 0x0 ==948== at 0x1: (within /root/test/App) Even if I put in debugging symbols, it doesn't give any more useful info. ldd shows all libraries being linked properly. Is there any other way I can find out what's wrong? I can't even do standard printf, cout, etc debugging. The executable doesn't even seem to start running at all. I rebuilt with symbols, and tried the suggestion below (gdb) break main Breakpoint 1 at 0x45470 (gdb) run Starting program: /root/test/App Breakpoint 1 at 0x80045470 Reading symbols from shared object read from target memory...done. Loaded system supplied DSO at 0xffffe000 Program received signal SIGSEGV, Segmentation fault. 0x00000001 in ?? () I checked for static initializers and I don't seem to have any. Yep, I tried printf, cout, etc. It doesn't even make it into the main routine, so I'm looking for problems with static initializers in link libraries, adding them in one-by-one. I'm not getting any stack traces either.

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• Android: onListItemClick not opening up the .xml file

  - by Capsud

  Hi, public void onListItemClick(ListView l, View v, int position, long id) { if(position == 0){ setContentView(R.layout.cuisine); } } I have an array of Strings and i'm using the above method to try and open up a new xml file called 'cuisine' when it is clicked. but it keeps failing! Have I done this right, or what am I doing wrong? Thanks. Ok from looking at similar problems on the web, people have said to get the onListItemClick() to start a new activity and using that new activity to then open up the new view? So what i've done is this... protected void onListItemClick(ListView l, View v, int position, long id) { Intent dundrumIntent = new Intent(v.getContext(), DundrumSelector.class); dundrumIntent.putExtra("position", position); startActivityForResult(dundrumIntent, 0); } and then import android.app.Activity; import android.os.Bundle; public class DundrumSelector extends Activity { @Override public void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); int position = getIntent().getExtras().getInt("position"); if(position == 0){ setContentView(R.layout.cuisine); } } } Yet i'm still getting the same problem. The program crashes when I click on an item in the listView. And yes i've added the activity to the manifest. Does anyone have a resolution to this as alot of people seem to be having the same problem. Thanks alot.

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