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• Problem with incomplete input when using Attoparsec

  - by Dan Dyer

  I am converting some functioning Haskell code that uses Parsec to instead use Attoparsec in the hope of getting better performance. I have made the changes and everything compiles but my parser does not work correctly. I am parsing a file that consists of various record types, one per line. Each of my individual functions for parsing a record or comment works correctly but when I try to write a function to compile a sequence of records the parser always returns a partial result because it is expecting more input. These are the two main variations that I've tried. Both have the same problem. items :: Parser [Item] items = sepBy (comment <|> recordType1 <|> recordType2) endOfLine For this second one I changed the record/comment parsers to consume the end-of-line characters. items :: Parser [Item] items = manyTill (comment <|> recordType1 <|> recordType2) endOfInput Is there anything wrong with my approach? Is there some other way to achieve what I am attempting?

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• Is locking on the requested object a bad idea?

  - by Quick Joe Smith

  Most advice on thread safety involves some variation of the following pattern: public class Thing { private static readonly object padlock = new object(); private string stuff, andNonsense; public string Stuff { get { lock (Thing.padlock) { if (this.stuff == null) this.stuff = "Threadsafe!"; } return this.stuff; } } public string AndNonsense { get { lock (Thing.padlock) { if (this.andNonsense == null) this.andNonsense = "Also threadsafe!"; } return this.andNonsense; } } // Rest of class... } In cases where the get operations are expensive and unrelated, a single locking object is unsuitable because a call to Stuff would block all calls to AndNonsense, degrading performance. And rather than create a lock object for each call, wouldn't it be better to acquire the lock on the member itself (assuming it is not something that implements SyncRoot or somesuch for that purpose? For example: public string Stuff { get { lock (this.stuff) { // Pretend that this is a very expensive operation. if (this.stuff == null) this.stuff = "Still threadsafe and good?"; } return this.stuff; } } Strangely, I have never seen this approach recommended or warned against. Am I missing something obvious?

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• How to get a debug flow of execution in C++

  - by Rich

  Hi, I work on a global trading system which supports many users. Each user can book,amend,edit,delete trades. The system is regulated by a central deal capture service. The deal capture service informs all the user of any updates that occur. The problem comes when we have crashes, as the production environment is impossible to re-create on a test system, I have to rely on crash dumps and log files. However this doesn't tell me what the user has been doing. I'd like a system that would (at the time of crashing) dump out a history of what the user has been doing. Anything that I add has to go into the live environment so it can't impact performance too much. Ideas wise I was thinking of a MACRO at the top of each function which acted like a stack trace (only I could supply additional user information, like trade id's, user dialog choices, etc ..) The system would record stack traces (on a per thread basis) and keep a history in a cyclic buffer (varying in size, depending on how much history you wanted to capture). Then on crash, I could dump this history stack. I'd really like to hear if anyone has a better solution, or if anyone knows of an existing framework? Thanks Rich

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• What's the most trivial function that would benfit from being computed on a GPU?

  - by hanDerPeder

  Hi. I'm just starting out learning OpenCL. I'm trying to get a feel for what performance gains to expect when moving functions/algorithms to the GPU. The most basic kernel given in most tutorials is a kernel that takes two arrays of numbers and sums the value at the corresponding indexes and adds them to a third array, like so: __kernel void add(__global float *a, __global float *b, __global float *answer) { int gid = get_global_id(0); answer[gid] = a[gid] + b[gid]; } __kernel void sub(__global float* n, __global float* answer) { int gid = get_global_id(0); answer[gid] = n[gid] - 2; } __kernel void ranksort(__global const float *a, __global float *answer) { int gid = get_global_id(0); int gSize = get_global_size(0); int x = 0; for(int i = 0; i < gSize; i++){ if(a[gid] > a[i]) x++; } answer[x] = a[gid]; } I am assuming that you could never justify computing this on the GPU, the memory transfer would out weight the time it would take computing this on the CPU by magnitudes (I might be wrong about this, hence this question). What I am wondering is what would be the most trivial example where you would expect significant speedup when using a OpenCL kernel instead of the CPU?

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• File upload fails when user is authenticated. Using IIS7 Integrated mode.

  - by Nikkelmann

  These are the user identities my website tells me that it uses: Logged on: NT AUTHORITY\NETWORK SERVICE (Can not write any files at all) and Not logged on: WSW32\IUSR_77 (Can write files to any folder) I have a ASP.NET 4.0 website on a shared hosting IIS7 web server running in Integrated mode with 32-bit applications support enabled and MSSQL 2008. Using classic mode is not an option since I need to secure some static files and I use Routing. In my web.config file I have set the following: <system.webServer> <modules runAllManagedModulesForAllRequests="true" /> </system.webServer> My hosting company says that Impersonation is enabled by default on machine level, so this is not something I can change. I asked their support and they referred me to this article: http://www.codinghub.net/2010/08/differences-between-integrated-mode-and.html Citing this part: Different windows identity in Forms authentication When Forms Authentication is used by an application and anonymous access is allowed, the Integrated mode identity differs from the Classic mode identity in the following ways: * ServerVariables["LOGON_USER"] is filled. * Request.LogognUserIdentity uses the credentials of the [NT AUTHORITY\NETWORK SERVICE] account instead of the [NT AUTHORITY\INTERNET USER] account. This behavior occurs because authentication is performed in a single stage in Integrated mode. Conversely, in Classic mode, authentication occurs first with IIS 7.0 using anonymous access, and then with ASP.NET using Forms authentication. Thus, the result of the authentication is always a single user-- the Forms authentication user. AUTH_USER/LOGON_USER returns this same user because the Forms authentication user credentials are synchronized between IIS 7.0 and ASP.NET. A side effect is that LOGON_USER, HttpRequest.LogonUserIdentity, and impersonation no longer can access the Anonymous user credentials that IIS 7.0 would have authenticated by using Classic mode. How do I set up my website so that it can use the proper identity with the proper permissions? I've looked high and low for any answers regarding this specific problem, but found nil so far... I hope you can help!

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• I have data about deadlocks, but I can't understand why they occur

  - by Alex

  I am receiving a lot of deadlocks in my big web application. http://stackoverflow.com/questions/2941233/how-to-automatically-re-run-deadlocked-transaction-asp-net-mvc-sql-server Here I wanted to re-run deadlocked transactions, but I was told to get rid of the deadlocks - it's much better, than trying to catch the deadlocks. So I spent the whole day with SQL Profiler, setting the tracing keys etc. And this is what I got. There's a Users table. I have a very high usable page with the following query (it's not the only query, but it's the one that causes troubles) UPDATE Users SET views = views + 1 WHERE ID IN (SELECT AuthorID FROM Articles WHERE ArticleID = @ArticleID) And then there's the following query in ALL pages: User = DB.Users.SingleOrDefault(u => u.Password == password && u.Name == username); That's where I get User from cookies. Very often a deadlock occurs and this second Linq-to-SQL query is chosen as a victim, so it's not run, and users of my site see an error screen. I read a lot about deadlocks... And I don't understand why this is causing a deadlock. So obviously both of this queries run very often. At least once a second. Maybe even more often (300-400 users online). So they can be run at the same time very easily, but why does it cause a deadlock? Please help. Thank you

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• Slow T-SQL query, convert to LINQ to Object

  - by yimbot

  I have a T-SQL query which populates a DataSet from an MSSQL database. string qry = "SELECT * FROM EvnLog AS E WHERE TimeDate = (SELECT MAX(TimeDate) From EvnLog WHERE Code = E.Code) AND (Event = 8) AND (TimeDate BETWEEN '" + Start + "' AND '" + Finish + "')" The database is quite large and being the type of nested query it is, the Data Adapter can take a number of minutes to fill the DataSet. I have extended the DataAdapter's timeout value to 480 seconds to combat it, but the client still complains about slow performance and occassional timeouts. To combat this, I was considering executing a simpler query (ie. just taking the date range) and then populating a Generic List which I could then execute a Linq query against. The simple query executes very quickly which is great. However, I cannot seem to build a Linq query which generates the same results as the T-SQL query above. Is this the best solution to this problem? Can anyone provide tips on rewriting the above T-SQL into Linq? I have also considered using a DataView, but cannot seem to get the results from that either.

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• measure the response time of a link

  - by Ahoura Ghotbi

  I am trying to create a simple load balance script and I was wondering if it is possible to find the response time of a server live? By that I mean is it possible to measure how long it takes for a server to respond after the request has been sent out? What I am trying to do is fairly simple, I want to send a request to a link/server and do a count down, if the server took more than 5 seconds to reply, I would like to fall on the backup server. Note that it doesnt have to be in pure php, I wouldnt mind using other languages such as javascript, C/C++, asp, but I prefer to do it in PHP. if it is possible to do the task, could you just point me to the right direction so I can read up on it. Clarification What I want to do is not to download a file and see how long it took, my servers have high load and it takes a while for them to respond when you click on a file to download, what I want to do is to measure the time it takes the server to respond (in this situation, its the time it takes the server to respond and allow the user to download the file), and if it takes longer than x seconds, it should fall back on a backup server.

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• How to create a String Array and link it to a Grade array

  - by user1861544

  I have a project that I need to create 2 Arrays, one to hold Student Names and one to hold Student Scores. The user inputs the size of the array, and the array needs to be sorted using BubbleSort (putting the high scores at the top). I have started the project, created the first array for scores, I have successfully done bubble sort and sorted the grades. Now I can't figure out how to make an array for Names, and once I do how do I make the names array correspond to the Grades array BubbleSort? Here is the code I have so far. import java.util.Scanner; public class Grades { public static void main(String[]args){ { Scanner UserIn = new Scanner(System.in); System.out.print( "How many students are there? " ); int[]GradeArray = new int[UserIn.nextInt()]; for( int i=0 ; i<GradeArray.length ; i++ ) { System.out.print( "Enter Grade for Student " + (i+1) + ": " ); GradeArray[i] = UserIn.nextInt(); } bubbleSort(GradeArray); for( int i : GradeArray ) System.out.println( i ); System.out.println(); } } private static void bubbleSort(int[]GradeArray){ int n = GradeArray.length; int temp = 0; String temp2; for(int i=0; i<n; i++){ for(int j=1; j<(n-i);j++){ if(GradeArray[j-1]<GradeArray[j]){ //swap temp=GradeArray[j-1]; GradeArray[j-1]=GradeArray[j]; GradeArray[j]=temp; } } } } } Also how do I change the grades to Double? I started with Int and when I try to change everything to double I get an error saying "Found Double, expected Int".

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• Freetype2 (error-)return value documentation

  - by Awaki

  In short, I'm looking for documentation that would limit the error situations to check for after a Freetype library function failed, much like the OpenGL and Win32 APIs document the error codes generated by their respective functions. I can't seem to find such documentation though, so I was wondering how to best handle translation of Freetype errors to typed exceptions. Background: I am currently in the process of implementing font-rendering capability (using Freetype) for my GUI framework, which makes strong use of typed exceptions to indicate error situations. However, the Freetype docs seem to completely omit what errors can be expected from what functions. That, if such documentation does indeed not exist, would basically leave me with two options: either guessing which errors make sense for a certain Freetype function (obviously prone to mistakes on my part), or considering every error code for translation into appropriate exceptions (less verbose since I would have to write the translation only once). Performance isn't really critical in the code that calls the Freetype library, so even the latter option would probably be acceptable, but surely there must be some kind of documentation on which library calls may return what Freetype error? Is there any such documentation which I just somehow managed to not find? Should I go the route of generically expecting every error code for translation? Or are there other ways to approach this problem? By the way, I wanted to avoid introducing some kind of generic FreetypeException (containing a description of the Freetype error) since I intended to completely hide what libraries I'm using (not from a legal point-of-view, mind you), but I guess I can be convinced to do this anyway if the consensus is that it would be the best option. I don't think it matters for this question, but I'm writing in C++.

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• Was Visual Studio 2008 or 2010 written to use multi cores?

  - by Erx_VB.NExT.Coder

  basically i want to know if the visual studio IDE and/or compiler in 2010 was written to make use of a multi core environment (i understand we can target multi core environments in 08 and 10, but that is not my question). i am trying to decide on if i should get a higher clock dual core or a lower clock quad core, as i want to try and figure out which processor will give me the absolute best possible experience with Visual Studio 2010 (ide and background compiler). if they are running the most important section (background compiler and other ide tasks) in one core, then the core will get cut off quicker if running a quad core, esp if background compiler is the heaviest task, i would imagine this would b e difficult to seperate in more then one process, so even if it uses multi cores you might still be better off with going for a higher clock cpu if the majority of the processing is still bound to occur in one core (ie the most significant part of the VS environment). i am a vb programmer, they've made great performance improvements in beta 2, congrats, but i would love to be able to use VS seamlessly... anyone have any ideas? thanks, erx

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• How would I compare two Lists(Of <CustomClass>) in VB?

  - by Kumba

  I'm working on implementing the equality operator = for a custom class of mine. The class has one property, Value, which is itself a List(Of OtherClass), where OtherClass is yet another custom class in my project. I've already implemented the IComparer, IComparable, IEqualityComparer, and IEquatable interfaces, the operators =, <>, bool and not, and overriden Equals and GetHashCode for OtherClass. This should give me all the tools I need to compare these objects, and various tests comparing two singular instances of these objects so far checks out. However, I'm not sure how to approach this when they are in a List. I don't care about the list order. Given: Dim x As New List(Of OtherClass) From {New OtherClass("foo"), New OtherClass("bar"), New OtherClass("baz")} Dim y As New List(Of OtherClass) From {New OtherClass("baz"), New OtherClass("foo"), New OtherClass("bar")} Then (x = y).ToString should print out True. I need to compare the same (not distinct) set of objects in this list. The list shouldn't support dupes of OtherClass, but I'll have to figure out how to add that in later as an exception. Not interested in using LINQ. It looks nice, but in the few examples I've played with, adds a performance overhead in that bugs me. Loops are ugly, but they are fast :) A straight code answer is fine, but I'd like to understand the logic needed for such a comparison as well. I'm probably going to have to implement said logic more than a few times down the road.

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• How can I measure the time it takes a file to upload to a PHP script?

  - by Gustav Bertram

  I am trying to measure the time a script takes to upload a file to a PHP script, inside the receiving script. Here's a short example: <form action="#" enctype="multipart/form-data" method="post"> Upload: <input type="file" name="datafile" size="40"> <input type="submit" value="Send"> </form> <?php $upload_time = time() - $_SERVER['REQUEST_TIME']; echo $upload_time . " seconds."; I've submitted 4MB, 25MB, 100MB and 1.4GB files. They took anything from a fraction of a second, to almost a minute, yet the script above always yielded 0 seconds. NOTE: I know that this is a duplicate question, but the accepted answer on the other question did not work for me (at least, initially): Detect how long it takes for a file to upload (PHP) I've tried it using PHP 5.3.3 with Apache 2.2.16 on Ubuntu 10.4. UPDATE: I've discovered that both the Apache header and Ajax solutions work. In fact, the solution on the duplicate question also works. The critical element to making these solutions work is to ensure that the following values in the php.ini are sufficiently high: memory_limit = 1000M upload_max_filesize = 1000M post_max_size = 1000M I am accepting the Apache header solution, since it only uses PHP.

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• File size monitoring in C#

  - by manemawanna

  Hello, I work in the Systems & admin team and have been given the task of creating a quota management application to try and encourage users to better manage there resources as we currently have issues with disc space and don't enforce hard quotas. At the moment I'm using the code below to go through all the files in a users homespace to retrieve the overall amount of space they are using. As from what I've seen else where theres no other way to do this in C#, the issue with it is theirs quite a high overhead while it retireves the size of each file then creates a total. try { long dirSize = 0; FileInfo[] FI = new DirectoryInfo("I:\\").GetFiles("*.*", SearchOption.AllDirectories); foreach (FileInfo F1 in FI) { dirSize += F1.Length; } return dirSize; } So I'm looking for a quicker way to do this or a quick way to monitor changes in the size of files while using the options avaliable through FileSystemWatcher. At the moment the only thing I can think of is creating a hashtable containing the file location and size of each file, so when a size changed event occurs I can compare the old size against the new one and update the total. Any suggestions would be greatly appreciated.

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• Better language or checking tool?

  - by rwallace

  This is primarily aimed at programmers who use unmanaged languages like C and C++ in preference to managed languages, forgoing some forms of error checking to obtain benefits like the ability to work in extremely resource constrained systems or the last increment of performance, though I would also be interested in answers from those who use managed languages. Which of the following would be of most value? A language that would optionally compile to CLR byte code or to machine code via C, and would provide things like optional array bounds checking, more support for memory management in environments where you can't use garbage collection, and faster compile times than typical C++ projects. (Think e.g. Ada or Eiffel with Python syntax.) A tool that would take existing C code and perform static analysis to look for things like potential null pointer dereferences and array overflows. (Think e.g. an open source equivalent to Coverity.) Something else I haven't thought of. Or put another way, when you're using C family languages, is the top of your wish list more expressiveness, better error checking or something else? The reason I'm asking is that I have a design and prototype parser for #1, and an outline design for #2, and I'm wondering which would be the better use of resources to work on after my current project is up and running; but I think the answers may be useful for other tools programmers also. (As usual with questions of this nature, if the answer you would give is already there, please upvote it.)

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• SQL Server 2008 R2

  - by kevchadders

  Hi all, I heard on the grapevine that Microsoft will be releasing SQL Server 2008 R2 within a year. Though I initially thought this was a patch for the just released 2008 version, I realised that it’s actually a completely different version that you would have to pay for. (Am I correct, if you had SQL Server 2008, would you have to pay again if you wanted to upgrade to 2008 R2?) If you’re already running SQL Server 2008, would you say it’s still worth the upgrade? Or does it depend on the size of your company and current setup. For what I’ve initially read, I do get the impression that this version would be more useful for the very high end hardware setup where you want to have very good scalability. With regard to programming, is there any extra enhancements/support in there which you’re aware of that will significantly help .NET Products/Web Development? Initially found a couple of links on it, but I was wondering if anyone had anymore info to share on subject as I couldn’t find nothing on SO about it? Thanks. New SQL Server R2 Microsoft Link on it. Microsoft SQL 2008 R2 EDIT: More information based on the Express Edition One very interesting thing about SQL Server 2008 R2 concerns the Express edition. Previous express versions of SQL Server Express had a database size limit of 4GB. With SQL Server Express 2008 R2, this has now been increased to 10GB !! This now makes the FREE express edition a much more viable option for small & medium sized applications that are relatively light on database requirements. Bear in mind, that this limit is per database, so if you coded your application cleverly enough to use a separate database for historical/archived data, you could squeeze even more out of it! For more information, see here: http://blogs.msdn.com/sqlexpress/archive/2010/04/21/database-size-limit-increased-to-10gb-in-sql-server-2008-r2-express.aspx

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• How to efficiently implement a strategy pattern with spring ?

  - by Anth0

  I have a web application developped in J2EE 1.5 with Spring framework. Application contains "dashboards" which are simple pages where a bunch of information are regrouped and where user can modify some status. Managers want me to add a logging system in database for three of theses dashboards. Each dashboard has different information but the log should be traced by date and user's login. What I'd like to do is to implement the Strategy pattern kind of like this : interface DashboardLog { void createLog(String login, Date now); } // Implementation for one dashboard class PrintDashboardLog implements DashboardLog { Integer docId; String status; void createLog(String login, Date now){ // Some code } } class DashboardsManager { DashboardLog logger; String login; Date now; void createLog(){ logger.log(login,now); } } class UpdateDocAction{ DashboardsManager dbManager; void updateSomeField(){ // Some action // Now it's time to log dbManagers.setLogger = new PrintDashboardLog(docId, status); dbManagers.createLog(); } } Is it "correct" (good practice, performance, ...) to do it this way ? Is there a better way ? Note :I did not write basic stuff like constructors and getter/setter.

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• How to control the "flow" of an ASP.NET MVC (3.0) web app that relies on Facebook membership, with Facebook C# SDK?

  - by Chad

  I want to totally remove the standard ASP.NET membership system and use Facebook only for my web app's membership. Note, this is not a Facebook canvas app question. Typically, in an ASP.NET app you have some key properties & methods to control the "flow" of an app. Notably: Request.IsAuthenticated, [Authorize] (in MVC apps), Membership.GetUser() and Roles.IsUserInRole(), among others. It looks like [FacebookAuthorize] is equivalent to [Authorize]. Also, there's some standard work I do across all controllers in my site. So I built a BaseController that overrides OnActionExecuting(FilterContext). Typically, I populate ViewData with the user's profile within this action. Would performance suffer if I made a call to fbApp.Get("me") in this action? I use the Facebook Javascript SDK to do registration, which is nice and easy. But that's all client-side, and I'm having a hard time wrapping my mind around when to use client-side facebook calls versus server-side. There will be a point when I need to grab the user's facebook uid and store it in a "profile" table along with a few other bits of data. That would probably be best handled on the return url from the registration plugin... correct? On a side note, what data is returned from fbApp.Get("me")?

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• Trouble deciding how to add popup menu to eclipse plugin using either action ObjectContributions or command handlers

  - by user1808408

  The issue is this: Most things I read on the web says that we should avoid actions when creating popup menus because the command framework allows for more decoupling. Example: http://wiki.eclipse.org/FAQ_What_is_the_difference_between_a_command_and_an_action%3F Fair enough. But I am having a heck of a time getting the command framework to add my menu when I right click on a .java file inside the editor, and only when I click inside the editor. I can get the menu to show (using 'with' and the activeEditor variable), but it also shows when I right click on the java file inside the package explorer, which I don't want. I suspect it's because the file is already open inside the editor. I also have a menu that gets added when I right click on the java file inside the package explorer, using IComplilationUnit. That works fine. So my problem is solved using a popup menu action for when I click inside the file. I also get access to to all the ISelection stuff there. But the coupling is to high and I lose the flexability of using handlers. I'm looking for either: Tell me I'm doing it the only way possible; or Tell me how to have my popup appear only when I right click on the java file editor. Regards

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• How do I become better in math, after being a programmer for several years.

  - by loxs

  I've had quite a weird career till now. First I graduated from a medical school. Then I went into marketing (pharmaceuticals). And then umm, after some time, I decided to go for my (till then) hobby and became a "professional" programmer. I've been quite successful at this ever since. I have quite some languages "under my belt". I earn not bad and I have been involved in the opensource community quite heavily. The thing is that I suck at math :). Well, not totally of course, as I get my work done. But I don't know how much I suck. And I don't know how to find out. Math has never really been of any priority during my middle/high school years. I only picked as little as I could afford, because I was always getting ready to go for Medicine. Of course I know the basics of algebra. Things like "normal" and square equations. Also the basics of geometry. But well, there are things that I have missed. And lately I am being fascinated by things like probability theory, infinity, chaos/order etc. But every time I try to learn something about these topics, I hit a wall of terminology, special symbols, and some special kind of thinking, that is quite like mine (a programmer), but also a lot different (and appears weird to me). So, what kinds of books would you recommend me? It's very hard to find something suitable. All that I find are either too easy (and boring) or totally impenetrable.

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• firefox does not load large size images

  - by Pradeep

  I am stuck with a kind of bug in FF, wherein it’s unable to load images of big size (I have 8 MB size of image) from the server. The loading of image is all fine on IE. I am still looking out for ways to get rid of this problem. I changed server(IIS) settings to allow bigger file sizes. Also, I used “load” event on image using JQuery and tried all sort of options listed here http://api.jquery.com/load-event/, but nothing worked so far. If anyone of you has come across any such similar problem, and a way to resolve it, it would be nice to hear from you Please note: high resolution images are part of the requirement. Code : <style> img { background-color: #FFFFFF; background-image: url(http://eremurus.hyd:8080/QMS/plugin/imagepanner/loader.gif); background-repeat: no-repeat; background-position: center center; } </style> <script src="../plugin/jquery-ui-1.8.7.custom/js/jquery-1.4.4.min.js" type="text/javascript"></script> <script> jQuery(document).ready(function($){ ///var _url = "http://eremurus.hyd:8080/QMS/plugin/imagepanner/floorPlan.jpg"; // set up the node / element _im =$("#main"); //_im.bind("load",function(){ $(this).fadeIn(); }); // set the src attribute now, after insertion to the DOM //_im.attr('src',_url); $("#main").one("load",function(){ alert('loaded'); }) .each(function(){ if(this.complete){ $(this).trigger("load"); } }); }); </script> </head> <body> <div id="target"><img id='main' src="http://eremurus.hyd:8080/QMS/plugin/imagepanner/floorPlan.jpg"> </img></div> </body> </html>

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• C++ BigInt multiplication conceptual problem

  - by Kapo

  I'm building a small BigInt library in C++ for use in my programming language. The structure is like the following: short digits[ 1000 ]; int len; I have a function that converts a string into a bigint by splitting it up into single chars and putting them into digits. The numbers in digits are all reversed, so the number 123 would look like the following: digits[0]=3 digits[1]=3 digits[2]=1 I have already managed to code the adding function, which works perfectly. It works somewhat like this: overflow = 0 for i ++ until length of both numbers exceeded: add numberA[ i ] to numberB[ i ] add overflow to the result set overflow to 0 if the result is bigger than 10: substract 10 from the result overflow = 1 put the result into numberReturn[ i ] (Overflow is in this case what happens when I add 1 to 9: Substract 10 from 10, add 1 to overflow, overflow gets added to the next digit) So think of how two numbers are stored, like those: 0 | 1 | 2 --------- A 2 - - B 0 0 1 The above represents the digits of the bigints 2 (A) and 100 (B). - means uninitialized digits, they aren't accessed. So adding the above number works fine: start at 0, add 2 + 0, go to 1, add 0, go to 2, add 1 But: When I want to do multiplication with the above structure, my program ends up doing the following: Start at 0, multiply 2 with 0 (eek), go to 1, ... So it is obvious that, for multiplication, I have to get an order like this: 0 | 1 | 2 --------- A - - 2 B 0 0 1 Then, everything would be clear: Start at 0, multiply 0 with 0, go to 1, multiply 0 with 0, go to 2, multiply 1 with 2 How can I manage to get digits into the correct form for multiplication? I don't want to do any array moving/flipping - I need performance!

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• iPhone OpenGLES: Textures are consuming too much memory and the program crashes with signal "0"

  - by CustomAppsMan

  I am not sure what the problem is. My app is running fine on the simulator but when I try to run it on the iPhone it crashes during debugging or without debugging with signal "0". I am using the Texture2D.m and OpenGLES2DView.m from the examples provided by Apple. I profiled the app on the iPhone with Instruments using the Memory tracer from the Library and when the app died the final memory consumed was about 60Mb real and 90+Mb virtual. Is there some other problem or is the iPhone just killing the application because it has consumed too much memory? If you need any information please state it and I will try to provide it. I am creating thousands of textures at load time which is why the memory consumption is so high. Really cant do anything about reducing the number of pics being loaded. I was running before on just UIImage but it was giving me really low frame rates. I read on this site that I should use OpenGLES for higher frame rates. Also sub question is there any way not to use UIImage to load the png file and then use the Texture class provided to create the texture for OpenGLES functions to use it for drawing? Is there some function in OpenGLES which will create a texture straight from a png file?

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• WCF with MANY database connections

  - by Jorge Dominguez

  I'm working in the development of an ERP type .Net WinForms application consuming a WCF service. It's to be used by many small companies (in the range of 100-200). Database is SQL Server 2008 and the service will be hosted as a Windows service. Even thought there will be a single DB Server, our customer insists in having separate databases for each company. That is because of stability/support concerns (like DB being damaged or took offline for some reason thus affecting all clients). Concerns coming from previous experiences (not necessarily with same platform). With a single database, connections to the DB would be opened at service start up and pooling used, but, I'm not sure how connections could be managed in a multiple DB scenario: Could a connection to the corresponding DB be opened and closed for each service request? would performance be acceptable? If a connection is opened and maintained for each company accessing the system, what's the practical limit of opened connections (to different databases)? It would be very interesting to hear your opinions and suggestions for this situation. Tanks

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• Index question: Select * with WHERE clause. Where and how to create index

  - by Mestika

  Hi, I’m working on optimizing some of my queries and I have a query that states: select * from SC where c_id ="+c_id” The schema of ** SC** looks like this: SC ( c_id int not null, date_start date not null, date_stop date not null, r_t_id int not null, nt int, t_p decimal, PRIMARY KEY (c_id, r_t_id, date_start, date_stop)); My immediate bid on how the index should be created is a covering index in this order: INDEX(c_id, date_start, date_stop, nt, r_t_id, t_p) The reason for this order I base on: The WHERE clause selects from c_id thus making it the first sorting order. Next, the date_start and date_stop to specify a sort of “range” to be defined in these parameters Next, nt because it will select the nt Next the r_t_id because it is a ID for a specific type of my r_t table And last the t_p because it is just a information. I don’t know if it is at all necessary to order it in a specific way when it is a SELECT ALL statement. I should say, that the SC is not the biggest table. I can say how many rows it contains but a estimate could be between <10 and 1000. The next thing to add is, that the SC, in different queries, inserts the data into the SC, and I know that indexes on tables which have insertions can be cost ineffective, but can I somehow create a golden middle way to effective this performance. Don't know if it makes a different but I'm using IBM DB2 version 9.7 database Sincerely Mestika

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