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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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  • 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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  • Python fCGI + sqlAlchemy = malformed header from script. Bad header=FROM tags : index.py

    - by crgwbr
    I'm writing an Fast-CGI application that makes use of sqlAlchemy & MySQL for persistent data storage. I have no problem connecting to the DB and setting up ORM (so that tables get mapped to classes); I can even add data to tables (in memory). But, as soon as I query the DB (and push any changes from memory to storage) I get a 500 Internal Server Error and my error.log records malformed header from script. Bad header=FROM tags : index.py, when tags is the table name. Any idea what could be causing this? Also, I don't think it matters, but its a Linux development server talking to an off-site (across the country) MySQL server.

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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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  • 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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  • 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 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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  • 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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  • 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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  • A good architecture is evil? Hardcode forever?

    - by igor
    I have worked in many companies. Most of all reached a big success in their field. Some times I found the code was written by owner or co-owner or the first developer of this company. It was strange from architectural point of view code or awful code styled, or hardcoded and so on. I know a couple of startups, that were grown up and were started from the "one night" code. Is it only way to get success to write code in this way? Why does a code written "on knee" but in time is better than delayed well thought-out one? What about future? Which way is the best: to write a good architecture, code and spend some more time at the startup or to write "fast" and hardcoded one that would be completely (partially) throw out (or maybe wouldn't) after some period of time (or never)?

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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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  • 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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  • Why is doing a top(1) on an indexed column in mssql slow?

    - by reinier
    I'm puzzled by the following. I have a DB with around 10 million rows, and (among other indices) on 1 column is an index. Now I have 700k rows where the campaignid is indeed 3835 For all these rows, the connectionid is the same. I just want to find out this connectionid. use messaging_db; SELECT TOP (1) connectionid FROM outgoing_messages WITH (NOLOCK) WHERE (campaignid_int = 3835) Now this query takes approx 30 seconds to perform! I (with my small db knowledge) would expect that it would take any of the rows, and return me that connectionid If I test this same query for a campaign which only has 1 entry, it goes really fast. So the index works. How would I tackle this and why does this not work?

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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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  • 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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  • 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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  • 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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  • expand a varchar column very slowly , why?

    - by francs
    Hi We need to modify a column of a big product table , usually normall ddl statments will be excutely fast ,but the above ddl statmens takes about 10 minnutes?I wonder know the reason! I just want to expand a varchar column?The following is the detailsl --table size wapreader_log= select pg_size_pretty(pg_relation_size('log_foot_mark')); pg_size_pretty ---------------- 5441 MB (1 row) --table ddl wapreader_log= \d log_foot_mark Table "wapreader_log.log_foot_mark" Column | Type | Modifiers -------------+-----------------------------+----------- id | integer | not null create_time | timestamp without time zone | sky_id | integer | url | character varying(1000) | refer_url | character varying(1000) | source | character varying(64) | users | character varying(64) | userm | character varying(64) | usert | character varying(64) | ip | character varying(32) | module | character varying(64) | resource_id | character varying(100) | user_agent | character varying(128) | Indexes: "pk_log_footmark" PRIMARY KEY, btree (id) --alter column wapreader_log= \timing Timing is on. wapreader_log= ALTER TABLE wapreader_log.log_foot_mark ALTER column user_agent TYPE character varying(256); ALTER TABLE Time: 603504.835 ms

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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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  • Is Python a beginner language or is it robust?

    - by orokusaki
    I am already working on some software in Python but I'm having one of those days where I step back and reflect just to make sure I'm not spinning my wheels. I know that Twitter launched with RoR because it was fast to build. Then they almost moved into another language in 2008 because of scalability issues. This has caused me to step back and introspect for a moment to make sure I'm heading down the right path. I've read in some tutorials and other places that Python is "a great first language" or a "nice beginner language" as though it's not capable of larger tasks. I look at it as Python can do what Java or ASP can but with about 1/4th of the code, not to mention I don't have to build or compile, etc. I've read that Java runs quite a few times faster than Python which is important of course, but then I read everywhere that hardware keeps getting cheaper and there are projects like Unladen Swallow by Google to make Python faster. Should I be concerned or is this just the remnants of Java developers?

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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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  • What is the fastest way to copy content of DVD to hard disc using Linux

    - by Ritesh
    I have gone through some of the links Which talks about fastest way of copying files in windows using FILE_FLAG_NO_BUFFERING and FILE_FLAG_OVERLAPPED . It also talks about how request made for read and write opeartions with BUFFER SIZE as 256KB and 128KB are faster than 1Mb .The link for that is :- Explanation for tiny reads (overlapped, buffered) outperforming large contiguous reads? I am also loking for a Similar method in linux Which allows me to copy the content of my DVD to Hard Disc in a fast Way . So I wanted to know Is there some file operation flags in Linux which would provide me the best result or Which way of Copy in Linux is the best ? My codes are all in c++.

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  • jQuery Tools - Range Input with Mousewheel support

    - by pspahn
    I've got a nice looking horizontal scroller that uses the Range Input feature of jQ Tools. Mouse wheel scrolling support would be awesome, and I'm sure it can work, just not sure how to get it set up. I've got the generic setup: var scroll = jQuery('#scroll'); jQuery(':range').rangeinput({ speed: 0, progress: true, onSlide: function(ev, step) { scroll.css({left: -step}); }, change: function(e, i) { scroll.animate({left: -i}, "fast"); } }); The doc page ( http://jquerytools.org/documentation/toolbox/mousewheel.html ) for mousewheel gives an example: $("#myelement").mousewheel(function(event, delta) { }); But I'm not sure how this hooks in. Other tools in the package simply allow the option: mousewheel: true Unfortunately that doesn't work on range input. Any advice appreciated. Thank you.

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  • Silverlight 4 application on localhost runs extremely slow

    - by rams
    Silverlight 4 app running in IE8 and hosted on VS2010 internal webserver. The website takes atleast a minute to download the xap and code runs slow on client (IE8). I am running the app in debug mode and have turned intellitrace off. Symbol loading is also turned off. However if I kill the VS webserver, clean the solution, the app runs fast. 3 debugging sessions later, the app slows to a crawl. Have also tried turning off McAfee live scanning but no use. Looked in event log for any clue but found none. What could be the cause of the slowness? TIA rams

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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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