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• How can two threads access a common array of buffers with minimal blocking ? (c#)

  - by Jelly Amma

  Hello, I'm working on an image processing application where I have two threads on top of my main thread: 1 - CameraThread that captures images from the webcam and writes them into a buffer 2 - ImageProcessingThread that takes the latest image from that buffer for filtering. The reason why this is multithreaded is because speed is critical and I need to have CameraThread to keep grabbing pictures and making the latest capture ready to pick up by ImageProcessingThread while it's still processing the previous image. My problem is about finding a fast and thread-safe way to access that common buffer and I've figured that, ideally, it should be a triple buffer (image[3]) so that if ImageProcessingThread is slow, then CameraThread can keep on writing on the two other images and vice versa. What sort of locking mechanism would be the most appropriate for this to be thread-safe ? I looked at the lock statement but it seems like it would make a thread block-waiting for another one to be finished and that would be against the point of triple buffering. Thanks in advance for any idea or advice. J.

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• google spreadsheet api from android: google-api-java-client or handmade?

  - by yetanothercoderu

  For working with google spreadsheet api from android (2.2) - google suggests using google-api-java-client for android. For that you have to include 5 jars to your android application: guava-r09.jar google-http-client-extensions-android2-1.6.0-beta.jar google-api-client-extensions-android2-1.6.0-beta.jar google-http-client-1.6.0-beta.jar google-api-client-1.6.0-beta.jar and digging into google-api-java-client javadocs for fast-changing api. Does it worth the effort? in term of android specifics and device fragmentation? Isn't it reasonable to write your own simple http response parser or take small existing library like google-spreadsheet-lib-android ? Thanks! UPD: choosed google-api-java-client finally as it has all routine stuff (like parsing http, xml) out of box

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• [JavaScript] Loading Google Maps API after the page is displayed

  - by Goro

  Hello, My landing page contains a big google maps portion, which slows down the loading time. I am trying to do the following: Load the static elements first so the page loads fast initially. Display a loading notification in the map placeholder so that the user knows that the map is coming up Load and display the map I have done this: $(document).ready(function() { map_initialize(); } map_initialize() being the function which loads the map into its container div. However, this still will not display the static elements fist. The page will wait until the map_initialize() is finished, then load the static elements at the same time as the map. Thanks,

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• Maximum Possible File Name Length in Windows Kernel

  - by Lambert

  I was wondering, what is the longest possible name length allowed by the Windows kernel? E.g.: I know the kernel uses UNICODE_STRING structures to hold all object paths, and since the byte length of a wide-character string is stored inside a USHORT, that allows for a maximum path length of 2^15 - 1 characters. Is there a similar, hard restriction on a file name (rather than path)? (I don't care if NTFS or FAT32 imposes a particular restriction; I'm looking for the longest possible theoretically allowed name in the kernel, assuming no additional file system or shell restrictions.) (Edit: For those wondering why this even matters, consider that normally, traversing a directory is achieved by FindFirstFile/FindNextFile calls, one call per file. Given the function named NtQueryDirectoryFile, which is the underlying system call and which returns multiple file names per call, it's actually possible to take advantage of this maximum-length restriction on the path to make an extremely-fast directory traverser that uses solely the stack as a buffer. Now I'm trying to extend that concept, and I need to know the maximum size of a file name.)

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• SQL Server 2008 Insert performance issue

  - by mithiya

  is there any way to increase performance of SQL server inserts, as you can see below i have used below sql 2005, 2008 and oracle. i am moving data from ORACLe to SQL. while inserting data to SQL i am using a procedure. insert to Oracles is very fast in compare to SQL, is there any way increase performance. or a better way to move data from Oracle to SQL (data size approx 100000 records an hour) please find below stats as i gathered, RUN1 and RUN2 time is in millisecond.

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• efficient way to detect if an image is empty

  - by Jos

  Hi, I need a very fast method to detect if an image is empty. Im my case then all pixels are white and transparant. The images are png's. My current method is to load them in a memory bitmap and check each pixel value, but this is way to slow. Is there a more efficient way? This is my current code: 'Lock the bitmap bits. Dim bmpData As System.Drawing.Imaging.BitmapData = bmp.LockBits(rectBmp, _ Drawing.Imaging.ImageLockMode.ReadOnly, bmp.PixelFormat) Try Dim x As Integer Dim y As Integer For y = 0 To bmpData.Height - 1 For x = 0 To bmpData.Width - 1 If System.Runtime.InteropServices.Marshal.ReadByte(bmpData.Scan0, (bmpData.Stride * y) + (4 * x) + 3) <> 0 Then Return True Exit For End If Next Next Finally bmp.UnlockBits(bmpData) End Try

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• keep open windows console after a python syntax error

  - by basweber

  File associations on my machine (winxp home) are such that a python script is directly opened with the python interpreter. If I double click on a python script a console window runs and every thing is fine - as long as there is no syntax error in the script. In that case the console window opens up for a moment but it is closed immediately. Too fast to read the error message. Of course their would be the possibility to manually open a console window and to execute the script by typing python myscript.py but I am sure that there is a more convenient (i.e. "double click based") solution.

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• How to stop/override a Jquery TimeOut function?

  - by Tom

  Hi, I have a small jquery snippet that displays notification message at the top of the screen in response to user actions on a page. The notification is often displayed after Ajax actions with dynamic content inside it. For example: $("#mini-txt").html("Thank you!"); $("#mini").fadeIn("fast"); setTimeout(function() {$("#mini").animate({height: "hide", opacity: "hide"}, "medium");}, 3000); The notification works well, except when a user does two or more actions in rapid succession, in which case the TimeOut function will confuse itself and the second message appears to come inside the previous 3000 milliseconds. Is there a way to "kill" the previous notification if a new action is performed. I've got no problem with the actions/selectors, just the TimeOut function.... either stopping it or overriding it somehow. Or perhaps there's a better alternative for getting the message to linger on the screen for a few seconds before disappearing? Thank you.

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• How might one develop a program like FRAPS?

  - by blood

  I would like to make a program to capture video. What is the best way to capture video? I know C++ and I'm learning assembly. I found in my assembly book that I can get data from the video card. Would that be the best way? I know FRAPS hooks into programs, but I would like my program to take video of the entire screen. I would like something something fast, with low memory usage if possible. A requirement is that the program must be usable on other computers, despite dissimilar hardware.

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• How do I enable automatic reloading of view files in development mode in JRuby on Rails?

  - by thekingoftruth

  I am developing an app in JRuby on Rails. For some reason, when I edit the view files, the development JRuby Mongrel server doesn't reload them. The perplexing thing is that after editing the controller files, the server reloads them just fine on the next request. This would be annoying even when using MRI Ruby, however starting up JRuby Mongrel after every view edit is much slower, and much more annoying. (Note that once it starts up it's quite fast, the only issue is startup--the JVM has to load up every time I start JRuby Mongrel.) I'm running JRuby 1.5.0, Rails 2.3.5, and Java 6.

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• Optimizing MySQL statement with lot of count(row) an sum(row+row2)...

  - by Zombies

  I need to use InnoDB storage engine on a table with about 1mil or so records in it at any given time. It has records being inserted to it at a very fast rate, which are then dropped within a few days, maybe a week. The ping table has about a million rows, whereas the website table only about 10,000. My statement is this: select url from website ws, ping pi where ws.idproxy = pi.idproxy and pi.entrytime > curdate() - 3 and contentping+tcpping is not null group by url having sum(contentping+tcpping)/(count(*)-count(errortype)) < 500 and count(*) > 3 and count(errortype)/count(*) < .15 order by sum(contentping+tcpping)/(count(*)-count(errortype)) asc; I added an index on entrytime, yet no dice. Can anyone throw me a bone as to what I should consider to look into for basic optimization of this query. The result set is only like 200 rows, so I'm not getting killed there.

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• How can I detect if a file is binary (non-text) in python?

  - by grieve

  How can I tell if a file is binary (non-text) in python? I am searching through a large set of files in python, and keep getting matches in binary files. This makes the output look incredibly messy. I know I could use grep -I, but I am doing more with the data than what grep allows for. In the past I would have just searched for characters greater than 0x7f, but utf8 and the like make that impossible on modern systems. Ideally the solution would be fast, but any solution will do.

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• What are some good ways to do intermachine locking?

  - by mike

  Our server cluster consists of 20 machines, each with 10 pids of 5 threads. We'd like some way to prevent any two threads, in any pid, on any machine, from modifying the same object at the same time. Our code's written in Python and runs on Linux, if that helps narrow things down. Also, it's a pretty rare case that two such threads want to do this, so we'd prefer something that optimizes the "only one thread needs this object" case to be really fast, even if it means that the "one thread has locked this object and another one needs it" case isn't great. What are some of the best practices?

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• Silverlight 3 ArcSegment to always draw circle's

  - by kapaboo

  Hi everyone, Ok, my arcSegment must always draw Circle's. For this reason I calculate the Arc's Width with the following formula: arcXRadius = (4 * Math.Pow(height, 2) + Math.Pow(distanceArcPoints, 2)) / (8 * height); so Arcs.Size = (arcXRadius,height) But seems that the height is scaled down when drawn. I want to add a small Circle to the Arc's middle (highest point) so when you drag it it changes the arc Height but also changes the Width so it will remain a circle. Here's how I calculate the Circle's (highest) point: Point middlePoint = GetMiddlePoint(arcPointA,arcPointB); double arcYRadius = arcSegment.Size.Height; if (arcYRadius <= 0) return middlePoint; double angle = arcSegment.RotationAngle; Point ellinewPoint = new Point(); ellinewPoint.X = Math.Cos((angle + 90) * Math.PI / 180) * arcYRadius + middlePoint.X; ellinewPoint.Y = Math.Sin((angle + 90) * Math.PI / 180) * arcYRadius + middlePoint.Y; Until Arc's.Size.Height Property gets Closer to the Width my Circle is not at the right Point. So maybe someone can give me a hint or tell me what am I doing wrong. Cheers, kapaboo

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• validate constructor arguments or method parameters with annotations, and let them throw an exceptio

  - by marius

  I am validating constructor and method arguments, as I want to the software, especially the model part of it, to fail fast. As a result, constructor code often looks like this public MyModelClass(String arg1, String arg2, OtherModelClass otherModelInstance) { if(arg1 == null) { throw new IllegalArgumentsException("arg1 must not be null"); } // further validation of constraints... // actual constructor code... } Is there a way to do that with an annotation driven approach? Something like: public MyModelClass(@NotNull(raise=IllegalArgumentException.class, message="arg1 must not be null") String arg1, @NotNull(raise=IllegalArgumentException.class) String arg2, OtherModelClass otherModelInstance) { // actual constructor code... } In my eyes this would make the actual code a lot more readable. In understand that there are annotations in order to support IDE validation (like the existing @NotNull annotation). Thank you very much for your help.

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• How to I correctly add brackets to this code

  - by Mohammad

  This code removes whites paces, (fyi: it's credited to be very fast) function wSpaceTrim(s){ var start = -1, end = s.length; while (s.charCodeAt(--end) < 33 ); //here while (s.charCodeAt(++start) < 33 ); //here also return s.slice( start, end + 1 ); } The while loops don't have brackets, how would i correctly add brackets to this code? while(iMean){ like this; } Thank you so much!

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• Recommendations for C# controls that can be used to create a hierarchical list of prioritised items?

  - by Mendokusai

  I need to be able to display and edit a hierarchical list of tasks in a C# app. It can either be a Windows form app, or ASP.NET. Basically, I want similar behaviour to the way Microsoft Project handles tasks. The control would need to: 1) Maintain a list of items made up of several fields 2) Each item can have a number of children (at least 3 levels of nesting) 3) It needs to be very easy to change the parents/children of an item 4) It needs to be very easy to edit the fields (as fast as changing cells in Excel) 5) It needs to be very easy to reorder the items by dragging and dropping or cut and paste 6) If I can easily connect the control to a database, even better Anyone got any recommendations for controls for me to look at?

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• Branching logic in an MVC view

  - by Alex Kilpatrick

  I find myself writing a lot of code in my views that looks like the code below. In this case, I want to add some explanatory HTML for a novice, and different HTML for an expert user. <% if (ViewData["novice"] != null ) { % some extra HTML for a novice <% } else { % some HTML for an expert <% } % This is presentation logic, so it makes sense that it is in a view vs the controller. However, it gets ugly really fast, especially when ReSharper wants to move all the braces around to make it even uglier (is there a way to turn that off for views?). My question is whether this is proper, or should I branch in the controller to two separate views? If I do two views, I will have a lot of duplicated HTML to maintain. Or should I do two separate views with a shared partial view of the stuff that is in common?

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• Whats the best data-structure for storing 2-tuple (a, b) which support adding, deleting tuples and c

  - by bhups

  Hi So here is my problem. I want to store 2-tuple (key, val) and want to perform following operations: - keys are strings and values are Integers - multiple keys can have same value - adding new tuples - updating any key with new value (any new value or updated value is greater than the previous one, like timestamps) - fetching all the keys with values less than or greater than given value - deleting tuples. Hash seems to be the obvious choice for updating the key's value but then lookups via values will be going to take longer (O(n)). The other option is balanced binary search tree with key and value switched. So now lookups via values will be fast (O(lg(n))) but updating a key will take (O(n)). So is there any data-structure which can be used to address these issues? Thanks.

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• Migrate from VB.net to C#

  - by rowmark

  Hello Experts, I have been developing applications using VB.net for the past 5 years. As I tried to learn Java earlier and found it very difficult for me I did stick on to VB.net. And for me C# is more or less similar to Java. Now I cannot get away with it. I have to code on C#. Is there a way I can get to speed with C# fast. I would really appreciate if you can let me know your thoughts and if there are any good resources I can try.

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• Delete element from array

  - by Julio Diaz

  Is there a way I can get rid of some elements in an array. for instance, if i have this array int testArray[] = {0,2,0,3,0,4,5,6} Is there a "fast" way to get rid of the elements that equal 0 int resultArray[] = {2,3,4,5,6} I tried this function but I got lost using Lists public int[] getRidOfZero(int []s){ List<> result=new ArrayList<>(); for(int i=0; i<s.length; i++){ if(s[i]<0){ int temp = s[i]; result.add(temp); } } return result.toArray(new int[]); }

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• Applying a pixel shader effect to a portion of an image

  - by Nick

  I have a ScrollViewer that contains a very large video (16 megapixel @ 10fps) and I want to apply a pixel shader effect to it. Given the size of the images I can't apply the effect directly to the image. So I apply the effect to the ScrollContentPresenter in the control style. Which is great, everything runs nice and fast. However, I'm also rendering annotations inside of the ScrollContentPresenter which I do NOT want effects applied to (but they need to move and scale along with the image). Is there to apply the effect just to the clipped and displayed portion of the image or do I need to build a rather more complex control?

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• jquery change function into code for plugin

  - by jaap Klevering

  Help would be greatly appreciated. What is the correct markup that would change this function into a plugin. I tried, but cant make it to work. $(document).ready(function(){ $('ul.tabNav a').click(function() { var curChildIndex = $(this).parent().prevAll().length + 1; $(this).parent().parent().children('.current').removeClass('current'); $(this).parent().addClass('current'); $(this).parent().parent().next('.tabContainer').children('.current').slideUp('fast',function() { $(this).removeClass('current'); $(this).parent().children('div:nth-child('+curChildIndex+')').slideDown('normal',function() { $(this).addClass('current'); }); }); return true; }); });

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• how to make a program like fraps.

  - by blood

  i want to make a program that will capture video. what if the best way to captrue the video, i know c++ and im learning assembly and i found in my assembly book i can get data from the video card i think? would that be the best way? i know fraps hooks into programs but i want my program to take the full screen? so i want something fast low memory useage if i can and something i can use on other computers with them having the same hardware.

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• Is it hard problem?

  - by Lukasz Lew

  I can't solve it: You are given 8 integers: A, B, C representing a line on a plane with equation A*x + B*y = C a, b, c representing another line x, y representing a point on a plane The two lines are not parallel therefore divide plane into 4 pieces. Point (x, y) lies inside of one these pieces. Problem: Write a fast algorithm that will find a point with integer coordinates in the same piece as (x,y) that is closest to the cross point of the two given lines. Note: This is not a homework, this is old Euler-type task that I have absolutely no idea how to approach.

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