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• Can piping of screen to file change the result of a C++ code?

  - by Biga

  I am having this very weird behaviour with a C++ code: It gives me different results when running with and without piping the screen to a file (reproducible in cygwin and linux). I mean, if I get the same executable and run it like './run' or run it like './run out.log', I get different results! I use std::cout to output to screen, all lines ending with endl; I use ifstream for the input file; I use ofstream for output, all lines ending with endl. I am using g++ 4. Any idea what is going on? UPDATE: I have hard-coded the input data, so 'ifstream' is not used, and problem persists. UPDATE 2: That's getting interesting. I have output three variables that are computed initially, and that's what I get with and without piping direct to screen: 0 -0.02 0 piped: 0 -0.02 1.04083e-17 So there's a round-off difference with and without piping the output! Now, why piping would interefere with an internal computation of the code?

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• different thread accessing MemoryStream

  - by Wayne

  There's a bit of code which writes data to a MemoryStream object directly into it's data buffer by calling GetBuffer(). It also uses and updates the Position and SetLength() properties appropriately. This code works purposes 99.9999% of the time. Literally. Only every so many 100,000's of iterations it will barf. The specific problem is that the memory.Position property suddenly returns zero instead of the appropriate value. However, code was added that checks for the 0 and throws an exception which include log of the MemoryStream properties like Position and Length in a separate method. Those return the correct value. Further addition shows that when this rare condition occurs, the memory.Position only has zero inside this particular method. Okay. Obviously, this must be a threading issue. But this code is well locked. However, the nature of this software is that it's organized by "tasks" with a scheduler and so any one of several actual O/S thread may run this code at any give time--but never more than one at a time. So it's my guess that ordinarily it so happens that the same thread keeps getting used for this method and then on a rare occasion a different thread get used. Then due to compiler optimizations, the different thread never gets the correct value. It gets a "stale" value. Ordinarily in a situation like this I would apply a "volatile" keyword to the variable in question. But that (those) variables are inside the MemoryStream object. Does anyone have any other idea? Or does this mean we have to implement our own MemoryStream object? (Just like we end up having to do with practically every collection in .NET?) It's a shame to have such an awesome platform as .NET and have virtually the entire system useless as-is for seriously parallelized applications. If I'm wrong or you have other ideas, please advise. Sincerely, Wayne

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• Creating and appending a big DOM with javascript - most optimized way?

  - by fenderplayer

  I use the following code to append a big dom on a mobile browser (webkit): 1. while(someIndex--) // someIndex ranges from 10 to possibly 1000 2. { 3. var html01 = ['<div class="test">', someVal,'</div>', 4. '<div><p>', someTxt.txt1, someTxt.txt2, '</p></div>', 5. // lots of html snippets interspersed with variables 6. // on average ~40 to 50 elements in this array 7. ].join(''); 8. var fragment = document.createDocumentFragment(), 9. div = fragment.appendChild(document.createElement('div')); 10. div.appendChild(jQuery(html01)[0]); 11. jQuery('#screen1').append(fragment); 12. } //end while loop 13. // similarly i create 'html02' till 'html15' to append in other screen divs Is there a better or faster way to do the above? Do you see any problems with the code? I am a little worried about line 10 where i wrap in jquery and then take it out.

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• Problem with checkboxes, sql select statements & php

  - by smokey20

  I am trying to display some rows from a database table based on choices submitted by the user. Here is my form code <form action="choice.php" method="POST" > <input type="checkbox" name="variable[]" value="Apple">Apple <input type="checkbox" name="variable[]" value="Banana">Banana <input type="checkbox" name="variable[]" value="Orange">Orange <input type="checkbox" name="variable[]" value="Melon">Melon <input type="checkbox" name="variable[]" value="Blackberry">Blackberry From what I understand I am placing the values of these into an array called variable. Two of my columns are called receipe name and ingredients(each field under ingredients can store a number of fruits). What I would like to do is, if a number of checkboxes are selected then the receipe name/s is displayed. Here is my php code. <?php // Make a MySQL Connection mysql_connect("localhost", "*****", "*****") or die(mysql_error()); mysql_select_db("****") or die(mysql_error()); $variable=$_POST['variable']; foreach ($variable as $variablename) { echo "$variablename is checked"; } $query = "SELECT receipename FROM fruit WHERE $variable like ingredients"; $row = mysql_fetch_assoc($result); foreach ($_POST['variabble'] as $ingredients) echo $row[$ingredients] . '<br/>'; ?> I am very new to php and just wish to display the data, I do not need to perform any actions on it. I have tried many select statements but I cannot get any results to display. My db connection is fine and it does print out what variables are checked. Many thanks in advance.

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• Self referencing userdata and garbage collection

  - by drtwox

  Because my userdata objects reference themselves, I need to delete and nil a variable for the garbage collector to work. Lua code: obj = object:new() -- -- Some time later obj:delete() -- Removes the self reference obj = nil -- Ready for collection C Code: typedef struct { int self; // Reference to the object // Other members and function references removed } Object; // Called from Lua to create a new object static int object_new( lua_State *L ) { Object *obj = lua_newuserdata( L, sizeof( Object ) ); // Create the 'self' reference, userdata is on the stack top obj->self = luaL_ref( L, LUA_REGISTRYINDEX ); // Put the userdata back on the stack before returning lua_rawgeti( L, LUA_REGISTRYINDEX, obj->self ); // The object pointer is also stored outside of Lua for processing in C return 1; } // Called by Lua to delete an object static int object_delete( lua_State *L ) { Object *obj = lua_touserdata( L, 1 ); // Remove the objects self reference luaL_unref( L, LUA_REGISTRYINDEX, obj->self ); return 0; } Is there some way I can set the object to nil in Lua, and have the delete() method called automatically? Alternatively, can the delete method nil all variables that reference the object? Can the self reference be made 'weak'?

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• How can I find out if the MainActivity is being paused from my Java class?

  - by quinestor

  I am using motion sensor detection in my application. My design is this: a class gets the sensor services references from the main activity and then it implements SensorEventListener. That is, the MainActivity does not listen for sensor event changes: public void onCreate(Bundle savedInstanceState) { // ... code mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE); mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); // The following is my java class, it does not extends any android fragment/activty mShakeUtil = new ShakeUtil(mSensorManager,mAccelerometer,this); // ..more code.. } I can't redesign ShakeUtil so it is a fragment nor activity, unfortunately. Now to illustrate the problem consider: MainActivity is on its way to be destroyed/paused. I.e screen rotation ShakeUtil's onSensorChanged(SensorEvent event) gets called in the process.. One of the things that happen inside onSensorChanged is a dialog interaction, which gives the error: java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState When the previous happens between MainActivity's onSaveInstanceState and onPause. I know this can be prevented if I successfully detect that MainActivity is being pause in ShakeUtil. How can I detect that MainActivity is being paused or onSaveInstanceState was called from ShakeUtil? Alternatively, how can I avoid this issue without making Shakeutil extend activity? So far I have tried with flag variables but that isn't good enough, I guess these are not atomic operations. I tried using Activity's isChangingConfigurations(), but I get an undocummented "NoSuchMethodFound" error.. I am unregistering the sensors by calling ShakeUtil when onPause in main ACtivity

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• Four-color theorem in Prolog (using a dynamic predicate)

  - by outa

  Hi, I'm working on coloring a map according to the four-color theorem (http://en.wikipedia.org/wiki/Four_color_theorem) with SWI-Prolog. So far my program looks like this: colour(red). colour(blue). map_color(A,B,C) :- colour(A), colour(B), colour(C), C \= B, C \= A. (the actual progam would be more complex, with 4 colors and more fields, but I thought I'd start out with a simple case) Now, I want to avoid double solutions that have the same structure. E.g. for a map with three fields, the solution "red, red, blue" would have the same structure as "blue, blue, red", just with different color names, and I don't want both of them displayed. So I thought I would have a dynamic predicate solution/3, and call assert(solution(A,B,C)) at the end of my map_color predicate. And then, for each solution, check if they already exist as a solution/3 fact. The problem is that I would have to assert something like solution(Color1,Color1,Color2), i.e. with variables in order to make a unification check. And I can't think of a way to achieve this. So, the question is, what is the best way to assert a found solution and then make a unification test so that "red, red, blue" would unify with "blue, blue, red"?

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• Image jQuery scroller in a container. (like facebook cropper) can't get values of position.

  - by Stefan

  Hey all. Having a reallllll mind pain. I have a php image uploader which is all good and sotring the file and the jquery ajax is returning the image in an ammended html div with a div set up like this: #crop-holder { width:80px; height:80px; margin:10px 10px 20px 10px; border:1px #c0c0c0 solid; overflow:hidden; cursor:move; } The image is viewing fine and I am using the jquery scrollview plugin: http://code.google.com/p/jquery-scrollview/ I have tried adding a few lines to the plugin to store variables of scrollTop and Left and then replacing two hidden input values with x and y in my page. And then on the returned ajax html in the div I am trying to on a button click (for example) retrieve the values of the two hidden inputs.... Heres what i added to the plugin (i'm no js expert!): .mouseout(function(){ var _m = this.m; var lasty = _m.scrollTop(); getElementById("ycord").value = lasty; var lastx = _m.scrollLeft(); getElementById("xcord").value = lastx; self.stopgrab(); }) Still no luck!! How can I get the scrollTop and scrollLeft and successfully prepare them for sending onto another php script!? Thanks:) stefpretty

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• Does it exist: smart pointer, owned by one object allowing access.

  - by Noah Roberts

  I'm wondering if anyone's run across anything that exists which would fill this need. Object A contains an object B. It wants to provide access to that B to clients through a pointer (maybe there's the option it could be 0, or maybe the clients need to be copiable and yet hold references...whatever). Clients, lets call them object C, would normally, if we're perfect developers, be written carefully so as to not violate the lifetime semantics of any pointer to B they might have...but we're not perfect, in fact we're pretty dumb half the time. So what we want is for object C to have a pointer to object B that is not "shared" ownership but that is smart enough to recognize a situation in which the pointer is no longer valid, such as when object A is destroyed or it destroys object B. Accessing this pointer when it's no longer valid would cause an assertion/exception/whatever. In other words, I wish to share access to data in a safe, clear way but retain the original ownership semantics. Currently, because I've not been able to find any shared pointer in which one of the objects owns it, I've been using shared_ptr in place of having such a thing. But I want clear owneship and shared/weak pointer doesn't really provide that. Would be nice further if this smart pointer could be attached to member variables and not just hold pointers to dynamically allocated memory regions. If it doesn't exist I'm going to make it, so I first want to know if someone's already released something out there that does it. And, BTW, I do realize that things like references and pointers do provide this sort of thing...I'm looking for something smarter.

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• Initializing Disqus comments in hidden element causes issue in FF 14.0.1

  - by Bazze

  This issue appears only in Firefox 14.0.1 (well I couldn't reproduce it in any other browser). If you put the code for Disqus comments inside an element that is hidden and wait until everything is fully loaded and then display the element using JavaScript, the comment box nor comments will show up. However if you resize the window, it'll show up immediately. It's working fine in latest version of Google Chrome and Safari though. What's causing this and how to fix it? Sample code to reproduce: <div id="test" style="display:none;"> <div id="disqus_thread"></div> <script type="text/javascript"> /* * * CONFIGURATION VARIABLES: EDIT BEFORE PASTING INTO YOUR WEBPAGE * * */ var disqus_shortname = 'onlinefunctions'; // required: replace example with your forum shortname /* * * DON'T EDIT BELOW THIS LINE * * */ (function() { var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true; dsq.src = 'http://' + disqus_shortname + '.disqus.com/embed.js'; (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq); })(); </script> <noscript>Please enable JavaScript to view the <a href="http://disqus.com/?ref_noscript">comments powered by Disqus.</a></noscript> <a href="http://disqus.com" class="dsq-brlink">comments powered by <span class="logo-disqus">Disqus</span></a> </div> <a href="#" onclick="document.getElementById('test').style.display = 'block'">show</a> I could post a link to a live example but I'm not sure about the policy of posting links here on Stack Overflow.

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• Bash PATH: How long is too long?

  - by ajwood

  Hi, I'm currently designing a software quarantine pattern to use on Ubuntu. I'm not sure how standard "quarantine" is in this context, so here is what I hope to accomplish... Inside a particular quarantine is all of the stuff one needs to run an application (bin, share, lib, etc.). Ideally, the quarantine has no leaks, which means it's not relying on any code outside of itself on the system. A quarantine can be defined as a set of executables (and some environment settings needed to make them run). I think it will be beneficial to separate the built packages enough such that upgrading to a newer version of the quarantine won't require rebuilding the whole thing. I'll be able to update just a few packages, and then the new quarantine can use some of old parts and some of the new parts. One issue I'm wondering about is the environment variables I'll be setting up to use a particular quarantines. Is there a hard limit on how big PATH can be? (either in number of characters, or in the number of directories it contains) Might a path be so long that it affects performance? Thanks very much, Andrew p.s. Any other wisdom that might help my design would be greatly appreciated :)

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• How to read the birthday_date from the Facebook API

  - by Steve

  I have been chasing my tail on this! And it should be so simple!! I have an app in FaceBook that is working fine. However, I need to get the user's birth date. I have successfully got the request for extended permissions, but cannot get the birthday_date out and into a variable/store in database. <?php require_once('facebook.php'); $facebook = new Facebook(array( 'appId' => 'xxxxx', 'secret' => 'yyyyyyy', 'cookie' => true )); if ($facebook->getSession()) { $uid = $facebook->getUser(); $fbme = $facebook->api('/me'); } else { $params = array( 'fbconnect'=>0, 'canvas'=>1, 'req_perms'=>'publish_stream','email','user_location','user_birthday' ); $loginUrl = $facebook->getLoginUrl($params); print "<script type='text/javascript'>top.location.href = '$loginUrl';</script>"; } $session = $facebook->getSession(); $token = $session['access_token']; I would be very grateful if someone could show me the PHP code that reads the extended permissions and places the results into variables. Thanks Steve

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• Safari and Chrome back button changes hidden and submit values in forms

  - by OverClocked

  The following problem happens on both Safari and Chrome, so probably a WebKit issue. Page A: a page that requires you to login to see, contains a form that has a type=submit button, with name=submit, and value=a Page B: some other page Page C: ask user to login page, contains a form with a type=submit button, with name=submit and value=c User visits page A, then page B. Then idles and the user's login session times out. User hits back button to go back to page A. Browser redirects user to page C. On Safari and Chrome, when C is rendered, the form on page C has the type=submit button, name=submit, but value shows up as "a". If you reload while on page C, "c" appears as the value of the name=submit button. The same problem appears with type=hidden input fields; when user hits back button, their values are also changed to some other value from some other form. Also, this problem also shows up w/o the redirect, with just submit then back. In this case the previous page renders with incorrect values for hidden and submit CGI variables. So far the only fix I can come up with is use Javascript to reset the type=hidden and type=submit variable values, after page C loads, to make sure the values are correct. But that's not clean and universally applicable. Short of WebKit fixing this error, has anyone ran into a better workaround? Thanks.

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• What is the right path for PHP includes on a Mac?

  - by skorned

  Running Mac OS X 10.5.8, with PHP 5.2.11 Pre-installed. Using Coda 1.6.10. I'm writing PHP files, and then preview them running from file, not server. This was working fine till I tried PHP includes. These don't work as a relative path, only as an absolute from the root of the drive. Is there any way I can use statements like include_once "common/header.php"; without specifying my entire file path like so : include_once "/Volumes/Macintosh HD/Users/neil/Desktop/Website/ColoredLists_v1.0/common/base.php"; ,where ColoredLists_v1.0 is the directory with all the website files in it. I tried solutions like prepending _SERVER[DOCUMENT_ROOT] or dirname(File) to the file paths, but that didn't work as the variables were not set. Is there any easy way to do this, or a configuration I can change so that it looks in a specific directory by default instead of looking at the drive root? Currently, echo_include_path shows .: When I include this line at the start of the script, it works: set_include_path('/Volumes/Macintosh HD/Users/neil/Desktop/Website/ColoredLists_v1.0'); However, if I want to do this for all my scripts, I can't seem to make the change permanent. Even after I edited the Unix include_path in my php.ini, it doesn't seem to work.

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• Javascript function objects, this keyword points to wrong object

  - by Rody van Sambeek

  I've got a problem concerning the javascript "this" keyword when used within a javascript functional object. I want to be able to create an object for handling a Modal popup (JQuery UI Dialog). The object is called CreateItemModal. Which i want to be able to instantiate and pass some config settings. One of the config settings. When the show method is called, the dialog will be shown, but the cancel button is not functioning because the this refers to the DOM object instead of the CreateItemModal object. How can I fix this, or is there a better approach to put seperate behaviour in seperate "classes" or "objects". I've tried several approaches, including passing the "this" object into the events, but this does not feel like a clean solution. See (simplified) code below: function CreateItemModal(config) { // initialize some variables including $wrapper }; CreateItemModal.prototype.show = function() { this.$wrapper.dialog({ buttons: { // this crashes because this is not the current object here Cancel: this.close } }); }; CreateItemModal.prototype.close = function() { this.config.$wrapper.dialog('close'); };

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• Organising UI code in .NET forms

  - by sb3700

  Hi I'm someone who has taught myself programming, and haven't had any formal training in .NET programming. A while back, I started C# in order to develop a GUI program to control sensors, and the project has blossomed. I was just wondering how best to organise the code, particularly UI code, in my forms. My forms currently are a mess, or at least seem a mess to me. I have a constructor which initialises all the parameters and creates events. I have a giant State property, which updates the Enabled state of all my form control as users progress through the application (ie: disconnected, connected, setup, scanning) controlled by a States enum. I have 3-10 private variables accessed through properties, some of which have side-effects in changing the values of form elements. I have a lot of "UpdateXXX" functions to handle UI elements that depend on other UI elements - ie: if a sensor is changed, then change the baud rate drop down list. They are separated into regions I have a lot of events calling these Update functions I have a background worker which does all the scanning and analysis. My problem is this seems like a mess, particularly the State property, and is getting unmaintainable. Also, my application logic code and UI code are in the same file and to some degree, intermingled which seems wrong and means I need to do a lot of scrolling to find what I need. How do you structure your .net forms? Thanks

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• Passing a outside variable into a <asp:sqldatasource> tag. ASP.NET 2.0

  - by MadMAxJr

  I'm designing some VB based ASP.NET 2.0, and I am trying to make more use of the various ASP tags that visual studio provides, rather than hand writing everything in the code-behind. I want to pass in an outside variable from the Session to identify who the user is for the query. <asp:sqldatasource id="DataStores" runat="server" connectionstring="<%$ ConnectionStrings:MY_CONNECTION %>" providername="<%$ ConnectionStrings:MY_CONNECTION.ProviderName %>" selectcommand="SELECT THING1, THING2 FROM DATA_TABLE WHERE (THING2 IN (SELECT THING2 FROM RELATED_DATA_TABLE WHERE (USERNAME = @user)))" onselecting="Data_Stores_Selecting"> <SelectParameters> <asp:parameter name="user" defaultvalue ="" /> </SelectParameters> </asp:sqldatasource> And on my code behind I have: Protected Sub Data_Stores_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.SqlDataSourceSelectingEventArgs) Handles Data_Stores.Selecting e.Command.Parameters("user").Value = Session("userid") End Sub Oracle squaks at me with ORA-01036, illegal variable name. Am I declaring the variable wrong in the query? I thought external variables share the same name with a @ prefixed. from what I understand, this should be placing the value I want into the query when it executes the select. EDIT: Okay, thanks for the advice so far, first error was corrected, I need to use : and not @ for the variable declaration in the query. Now it generates an ORA-01745 invalid host/bind variable name. EDIT AGAIN: Okay, looks like user was a reserved word. It works now! Thanks for other points of view on this one. I hadn't thought of that approach.

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• How to make command-line options mandatory with GLib?

  - by ahe

  I use GLib to parse some command-line options. The problem is that I want to make two of those options mandatory so that the program terminates with the help screen if the user omits them. My code looks like this: static gint line = -1; static gint column = -1; static GOptionEntry options[] = { {"line", 'l', 0, G_OPTION_ARG_INT, &line, "The line", "L"}, {"column", 'c', 0, G_OPTION_ARG_INT, &column, "The column", "C"}, {NULL} }; ... int main(int argc, char** argv) { GError *error = NULL; GOptionContext *context; context = g_option_context_new ("- test"); g_option_context_add_main_entries (context, options, NULL); if (!g_option_context_parse(context, &argc, &argv, &error)) { usage(error->message, context); } ... return 0; } If I omit one of those parameters or both on the command-line g_option_context_parse() still succeeds and the values in question (line and or column) are still -1. How can I tell GLib to fail parsing if the user doesn't pass both options on the command-line? Maybe I'm just blind but I couldn't find a flag I can put into my GOptionEntry data structure to tell it to make those fields mandatory. Of course I could check if one of those variables is still -1 but then the user could just have passed this value on the command-line and I want to print a separate error message if the values are out of range.

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• What's a good way to parameterize "static" content (e.g. CSS) in a Tomcat webapp?

  - by Steven Huwig

  Some of our CSS files contain parameters that can vary based on the deployment location (dev, QA, prod). For example: background: url(#DOJO_PATH#/dijit/themes...) to avoid hardcoding a path to a particular CDN or locally-hosted Dojo installation. These values are textually substituted with the real values by a deployment script, when it copies the contents of the webapp into the Tomcat webapps directory. That way the same deployment archive file (WAR + TAR file containing other configuration) can be deployed to dev, QA, and prod, with the varying parameters provided by environment-specific configuration files. However, I'd like to make the contents of the WAR (including the templatized CSS files) independent of this in-house deployment script. Since we don't really have control over the deployment script, all I can think to do is configure Tomcat with #DOJO_PATH# etc. as environment variables in the application's context.xml, and use Tomcat to insert those parameters into the CSS at runtime. I could make the CSS files into generated JSPs, but it seems a little ugly to me. Moreover, the substitution only needs to be done once per application deployment, so repeatedly dynamically generating the stylesheets using JSP will be rather wasteful. Does anyone have any alternative ideas or tools to use for this? We're committed to Tomcat and to substituting these parameters at deployment or at runtime (that is, not at build time).

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• Identical files from different servers. Why might IE 8 display them differently?

  - by jasongetsdown

  I'm working on a site that will go on my company's intranet. I developed it locally on my computer, checking it in different browsers and on colleague's computers, and when it was done I handed it off to IT. They put identical copies on a staging server, and on the production server. This is a site built only with html, javascript, and css. No server side scripting. It also uses a DWF viewer plugin from Autodesk. It is a single standalone page (not part of a CMS) that allows users to load drawings into the viewer and then click to see info from a database of space info saved in a series of js arrays (the space DB software spits out a js file with all the info listed in array literals, creating a crap ton of global variables - ugh, but I digress). When I followed their links (using IE 8) the version on the staging server looked as expected, but the layout is hosed on the version from the production server. Specifically, it seems like a div that is supposed to flow to the right of a div that is float: left is displaying below the floated div at full width, as though it was clear: left (which it is not). It also has the wrong height. I downloaded the files from each and they are identical to my local version. Frustrated, I cleared my browser's cache, restarted my computer, checked it on a colleague's computer who also has IE 8. All the same issue. Staging server good. Production server bad. Finally I uninstalled IE 8 and looked at it in IE 6. Both versions looked fine. So, to recap. Two different servers. No server side scripting. Identical files. One browser agrees they are identical, the other does not. What could cause this?

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• Gradual memory leak and slowdown in loop

  - by Benji XVI

  I have a simple foundation tool that exports every frame of a movie as a .tiff file. Here is the relevant code: NSString* movieLoc = [NSString stringWithCString:argv[1]]; QTMovie *sourceMovie = [QTMovie movieWithFile:movieLoc error:nil]; int i=0; while (QTTimeCompare([sourceMovie currentTime], [sourceMovie duration]) != NSOrderedSame) { // save image of movie to disk NSAutoreleasePool *arp = [[NSAutoreleasePool alloc] init]; NSString *filePath = [NSString stringWithFormat:@"/somelocation_%d.tiff", i++]; NSData *currentImageData = [[sourceMovie currentFrameImage] TIFFRepresentation]; [currentImageData writeToFile:filePath atomically:NO]; NSLog(@"%@", filePath); [sourceMovie stepForward]; [arp release]; } [pool drain]; return 0; As you can see, in order to prevent very large memory buildups with the various transparently-autoreleased variables in the loop, we create, and flush, an autoreleasepool with every run through the loop. However, over the course of stepping through a movie, the amount of memory used by the program still gradually increases, and the speed at which frames are processed drops precipitously. (From ~0.5 seconds per frame at the start, to ~2 seconds per frame by the 250th frame.) The only thing I can think can be causing the gradual memory leak is a buildup of the NSAutoreleasePool objects themselves. Am I right in thinking they will only be deallocated when the outer pool is released? If so, is there a better memory management solution here? Creating a pool every run through the loop seems a little hacky. And if not, what is causing the slow memory leak? (It is not NSStrings, and much too slow to be NSImages or NSDatas.) And what could be causing the slowdown?

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• Need help with threads in a client/server

  - by nunos

  For college, I am developing a local relay chat. I have to program a chat server and client that will only work on sending messages on different terminal windows on the same computer with threads and fifos. The fifos part I am having no trouble, the threads part is the one that is giving me some headaches. The server has one thread for receiving commands from a fifo (used by all clients) and another thread for each client that is connected. For each client that is connected I need to know a certain information. Firstly, I was using global variables, which worked as longs as there was only one client connected, which is much of a chat, to chat alone. So, ideally I would have some data like: -nickname -name -email -etc... per client that is connected. However, I don't know how to do that. I could create a client_data[MAX_NUMBER_OF_THREADS] where client_data was a struct with everything I needed to have access to, but this would require to, in every communication between server and client to ask for the id of the client in the array client_data and that does not seem very pratical I could also instantiate a client_data immediately after creating the thread but it would only be available in that block, and that is not very pratical either. As you can see I am in need of a little guidance here. Any comment, piece of code or link to any relevant information is greatly appreciated. Thanks.

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• Is there any point in using a volatile long?

  - by Adamski

  I occasionally use a volatile instance variable in cases where I have two threads reading from / writing to it and don't want the overhead (or potential deadlock risk) of taking out a lock; for example a timer thread periodically updating an int ID that is exposed as a getter on some class: public class MyClass { private volatile int id; public MyClass() { ScheduledExecutorService execService = Executors.newScheduledThreadPool(1); execService.scheduleAtFixedRate(new Runnable() { public void run() { ++id; } }, 0L, 30L, TimeUnit.SECONDS); } public int getId() { return id; } } My question: Given that the JLS only guarantees that 32-bit reads will be atomic is there any point in ever using a volatile long? (i.e. 64-bit). Caveat: Please do not reply saying that using volatile over synchronized is a case of pre-optimisation; I am well aware of how / when to use synchronized but there are cases where volatile is preferable. For example, when defining a Spring bean for use in a single-threaded application I tend to favour volatile instance variables, as there is no guarantee that the Spring context will initialise each bean's properties in the main thread.

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• return ArrayList from spring controller for ajax call and render in second dropdown

  - by user1708125

  I've a spring bean with 3 Maps all of which are to be populated incrementally. First map is an item category list, second map is a product list and third map is a hobby for item type list All the maps are mapped to and on the JSP. When the page is loaded only the first map is populated on the onchange event of first map, I need to populate the second map in the bean and similarly on the onchange event of second map, I need to populate the third map in the bean. Is there a way to do this using Ajax?? I need some code samples to how to render JSON response in second and third dropdown. Clarification: @Donal: I have a simple JSP page with 3 dropdowns corresponding to 3 maps stored in my commandBean. So when the page loads for the first time only the first map and hence the first dropdown is populated. Now whenever the user selects anything out of the first dropdown, I need to send the same commandbean back with the values of the first dropdown and get the values for the second map and hence the second dropdown and so forth for the 3rd dropdown as well. For each dropdown I 've got 3 maps and 3 variables for storing the selected values. Now I want to understand if this is possible using Ajax. I hope this clarifies whatever you need to know. Thanx

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• Pointing to array element

  - by regular

  What I'm trying to achieve is say i have an array, i want to be able to modify a specific array element throughout my code, by pointing at it. for example in C++ i can do this int main(){ int arr [5]= {1,2,3,4,5}; int *c = &arr[3]; cout << arr[3] <<endl; *c = 0; cout << arr[3]<<endl; } I did some googling and there seems to be a way to do it through 'unsafe', but i don't really want to go that route. I guess i could create a variable to store the indexes, but I'm actually dealing with slightly more complexity (a list within a list. so having two index variables seems to add complexity to the code.) C# has a databinding class, so what I'm currently doing is binding the array element to a textbox (that i have hidden) and modifying that textbox whenever i want to modify the specific array element, but that's also not a good solution (since i have a textbox that's not being used for its intended purpose - a bit misleading).

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