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• Java concurrency - Should block or yield?

  - by teto

  Hi, I have multiple threads each one with its own private concurrent queue and all they do is run an infinite loop retrieving messages from it. It could happen that one of the queues doesn't receive messages for a period of time (maybe a couple seconds), and also they could come in big bursts and fast processing is necessary. I would like to know what would be the most appropriate to do in the first case: use a blocking queue and block the thread until I have more input or do a Thread.yield()? I want to have as much CPU resources available as possible at a given time, as the number of concurrent threads may increase with time, but also I don't want the message processing to fall behind, as there is no guarantee of when the thread will be reescheduled for execution when doing a yield(). I know that hardware, operating system and other factors play an important role here, but setting that aside and looking at it from a Java (JVM?) point of view, what would be the most optimal?

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• Efficient mapping for a particular finite integer set

  - by R..

  I'm looking for a small, fast (in both directions) bijective mapping between the following list of integers and a subset of the range 0-127: 0x200C, 0x200D, 0x200E, 0x200F, 0x2013, 0x2014, 0x2015, 0x2017, 0x2018, 0x2019, 0x201A, 0x201C, 0x201D, 0x201E, 0x2020, 0x2021, 0x2022, 0x2026, 0x2030, 0x2039, 0x203A, 0x20AA, 0x20AB, 0x20AC, 0x20AF, 0x2116, 0x2122 One obvious solution is: y = x>>2 & 0x40 | x & 0x3f; x = 0x2000 | y<<2 & 0x100 | y & 0x3f; Edit: I was missing some of the values, particularly 0x20Ax, which don't work with the above. Another obvious solution is a lookup table, but without making it unnecessarily large, a lookup table would require some bit rearrangement anyway and I suspect the whole task can be better accomplished with simple bit rearrangement. For the curious, those magic numbers are the only "large" Unicode codepoints that appear in legacy ISO-8859 and Windows codepages.

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• Writing at the end of file

  - by user342534

  Hi, I'm working on a system that requires high file I/O performance (with C#). Basically, I'm filling up large files (~100MB) from the start of the file until the end of the file. Every ~5 seconds I'm adding ~5MB to the file (sequentially from the start of the file), on every bulk I'm flushing the stream. Every few minutes I need to update a structure which I write at the end of the file (some kind of metadata). When flushing each one of the bulks I have no performance issue. However, when updating the metadata at the end of the file I get really low performance. My guess is that when creating the file (which also should be done extra fast), the file doesn't really allocates the entire 100MB on the disk and when I flush the metadata it must allocates all space until the end of file. Guys/Girls, any Idea how I can overcome this problem? Thanks a lot!

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• PHP : flatten array - fastest way?

  - by Industrial

  Is there any fast way to flatten an array and select subkeys ('key'&'value' in this case) without running a foreach loop, or is the foreach always the fastest way? Array ( [0] => Array ( [key] => string [value] => a simple string [cas] => 0 ) [1] => Array ( [key] => int [value] => 99 [cas] => 0 ) [2] => Array ( [key] => array [value] => Array ( [0] => 11 [1] => 12 ) [cas] => 0 ) ) To: Array ( [int] => 99 [string] => a simple string [array] => Array ( [0] => 11 [1] => 12 ) )

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• Speed of interpolation algorithms, C# and C++ working together.

  - by Kaminari

  Hello. I need fast implementation of popular interpolation algorithms. I figured it out that C# in such simple algorithms will be much slower than C++ so i think of writing some native code and using it in my C# GUI. First of all i run some tests and few operations on 1024x1024x3 matrix took 32ms in C# and 4ms in C++ and that's what i basicly need. Interpolation however is not a good word because i need them only for downscaling. But the question is: Will it be faster than C# methods in Drawing2D Image outputImage = new Bitmap(destWidth, destHeight, PixelFormat.Format24bppRgb); Graphics grPhoto = Graphics.FromImage(outputImage); grPhoto.InterpolationMode = InterpolationMode.*; //all of them grPhoto.DrawImage(bmp, new Rectangle(0, 0, destWidth, destHeight), Rectangle(0, 0, sourceWidth, sourceHeight), GraphicsUnit.Pixel); grPhoto.Dispose(); Some of these method run in 20ms and some in 80. Is there a way to do it faster?

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• Android:simulating 1-bit display

  - by user1681805

  I'm new to Android,trying to build a simple game which use 1-bit black and white display.the screen dimension is 160 * 80,that is 12800 pixels.I created a byte array for the "VRAM",so each time it draws,it first checks the array. The thing is that I am not drawing a point or rectangle for each pixel,I'm using 2 bitmaps(ARGB_4444,I have to use alpha channel,because of shadow effect),1 for positive and 1 for negative.So I called 12800 times drawBitmap() in the surfaceView's Draw method.I know that's silly...But even for openGL,12800 quards won't be that fast right? Sorry..I cannot post imgs.the link of screenshot:http://i1014.photobucket.com/albums/af267/baininja/Screenshot_2013-10-22-01-05-36_zps91dbcdef.png should i totally give up this and draw points on a 160*80 bitmap then scale it to intented size?But that loses the visual effects.

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• mysql query takes 145 seconds

  - by suomee

  I have a a mysql db with myisam engine. Along with many other table I have this table "et" which has around 8137037 records. I have created indexes (individual index of column hname and pnum, it did not help much later created joint index of hname and pnum and it help execute within a second)such that queries like "select st from et where hname='name' and pnum='1' limit 1;" execute fast (with in a second) but the problem is I must execute this query "select st from et where hname='name' and pnum='1' order by id limit 1" where id is the primary key of the table and this query sometimes take 145 seconds :( how can i resolve this issue?

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• PHP cURL loading delay

  - by lasquarte

  Hello. My problem is, I need to cURL-load a page that uses Ajax-based search, to get results of that search. And I need to organize a delay between curl_exec() and value returning. In other words, I need to execute curl_exec() for no less than 5 seconds. sleep() seems to stop curl execution and does not work. Will greatly appreciate any hint or clue UPD I don't know how, but on this page http://vkontakte.ru/gsearch.php?section=video&q=sample&name=1, but it requires an account to access curl DOES capture the search made by ajax. But if page tooks too long to load, Ajax returns "action was too fast" error. So I just need to prolong curl execution. Sorry if being unclear.

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• How to tell if there is an available thread in a thread pool in java

  - by Gormcito

  I am trying to proccess a queue of tasks from a database table as fast as possible while also limiting the number of threads to process the tasks. I am using a fixed sized thread pool with Executors.newFixedThreadPool(N); I want to know if there is a way of knowing if the thread pool is full, by that I mean are there currently 50 threads running, if so then I'll wait for a thread to be available before starting a new one instead of sleeping the main thread. Code of what I would like to do: ExecutorService executor = Executors.newFixedThreadPool(N); ResultSet results; while( true ) { results = getWaitingTasksStmt.executeQuery(); while( results.next() && executor.notFull() ) { executor.submit( new thread( new runnableInheritedClass(results) ) ); } }

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• Choosing an alternative ( visual basic) high level programming language

  - by user370244

  I used to be visual basic 6 programmer, i was pleased with visual basic : it is high level language that do stuff fast,easy to learn, easy to do stuff in,you can drag and drop stuff to the form and write your code,it is simply amazing.however microsoft buried VB6 and pointed us to VB.NET which is so different that it is not the old VB anymore.I didn't like what microsoft did and would like to look somewhere AWAY from microsoft and from any other proprietary language . I would like to look into a similar language that is easy,cross platform (windows / Linux), object oriented, visual design, non proprietary and compile (for some guarding against reverse engineering). i am freelancer so the choice is entirely mine,i don't care about performance of programs, the time taken to develop a given programs is much more important. desktop / database / GUI /networking programming is what i am looking for. so any such language offered by our open source community ? thank you so much

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• Gradient boosting predictions in low-latency production environments?

  - by lockedoff

  Can anyone recommend a strategy for making predictions using a gradient boosting model in the <10-15ms range (the faster the better)? I have been using R's gbm package, but the first prediction takes ~50ms (subsequent vectorized predictions average to 1ms, so there appears to be overhead, perhaps in the call to the C++ library). As a guideline, there will be ~10-50 inputs and ~50-500 trees. The task is classification and I need access to predicted probabilities. I know there are a lot of libraries out there, but I've had little luck finding information even on rough prediction times for them. The training will happen offline, so only predictions need to be fast -- also, predictions may come from a piece of code / library that is completely separate from whatever does the training (as long as there is a common format for representing the trees).

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• php vs python django or something else for CMS module

  - by Michael

  We're looking to develop a CMS module for our website and I need some help in choosing the language/framework for this project. Basically we need to develop a "help' module like this one from ebay http://pages.ebay.com/help/index.html which will contain a lot of static pages with nice URLs for SEO. The application must run fast using low computer resources. We have been looking to use php on a custom made mvc framework but we received advice from other sources that py/django is the exactly language/framework that we need in terms of maintainability and development speed because it was developed for exactly this kind of projects so I need an expert advice on this matter with pro and cons for each choice.

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• Will Haskell be a good choice for my task?

  - by Narzanka

  I'm starting a new project and don't know which language to use. My 'must have' requirements are: Be able to run on Windows/LinuxMacOs natively (native executable) - user should be able to just run the exe (when on Windows for example) and see the results. No runtimes/interpreters (no jvm, clr, etc) - one file download should be enough to run the application. Full unicode support. Be able to manipulate OS threads (create them, run multiple tasks in parallel on multi-core CPUs, etc). Be reasonably fast (Python level performance and better). To have some kind of standard library that does low-level, mundane tasks. Not very niche and have some community behind it to be able to ask questions. My 'nice to have' requirements are: Language should be functional It should have good string manipulation capabilities (not necessarily regex) Not extremely hard to learn I'm thinking about Haskell now but keeping in mind OCaml as well. Please advice if my choice is correct.

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• SSRS Performance Mystery

  - by user101654

  I have a stored procedure that returns about 50000 records in 10sec using at most 2 cores in SSMS. The SSRS report using the stored procedure was taking 20min and would max out the processor on an 8 core server for the entire time. The report was relatively simple (i.e. no graphs, calculations). The report did not appear to be the issue as I wrote the 50K rows to a temp table and the report could display the data in a few seconds. I tried many different ideas for testing altering the stored procedure each time, but keeping the original code in a separate window to revert back to. After one Alter of the stored procedure, going back to the original code, the report and server utilization started running fast, comparable to the performance of the stored procedure alone. Everything is fine for now, but I am would like to get to the bottom of what caused this in case it happens again. Any ideas?

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• How to make a staging table in ms sql 2005?

  - by chobo2

  Hi I heard about doing staging tables and I am wondering how you actually do it. I want to do a sqlbulk copy into a staging table. Then then update the real table. I heard in mssql 2008 that you can use something called merge but I am using ms sql 2005 so I heard I have to use a update inner join? I am not sure how that would look like(I am guessing best way would be to write it in SP). Also the staging table needs to be able to handle concurrent updates. I was thinking of putting another column in the staged as GUID so that way I know which records belong to which group and when it is time to delete the records from the staged table I can just use that. So can anyone show me any examples or tutorials on how to do it? Also how fast is this way? Say if your updating 50,000 records how long would that take(a guesstimate is fine)

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• Distribution of many small classes

  - by Moo-Juice

  Hi All, I have a base class called EventArgs. Derived from this are many, many specializations that represent event arguments for a particular kind of event. Consumers of these events may need some, many, or very few of these argument classes. My question is, would you provide a header file for each type (e.g, 50+ header files for the varying ones), would you try to group them in to families and have a 'common' header file for those, or would you throw caution to the window and throw them in to one easy-of-use header file that can just be included? Another approach might be to have 50 header files, and then I could introduce some "family" header files that included particular ones. Not sure about the naming conventions for these kinds of things so it is obvious what is where. I know there may not be a hard and fast rule, but wondering what other developers have done when they find themselves writing many little classes. Thanks in advance.

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• How can i add Active Directory security groups to a SharePoint site to control permissions, rather than individual user accounts

  - by user574811

  SharePoint does integrate active directory accounts, of course, but how about security groups? Have a few sites where I'm fairly confident access is going through an existing Active Directory (AD) security groups (i.e. only an AD security group has been granted permissions through the 'People and Groups') In another situation, where I created the AD group and granted it permissions to a site, the customers were not able to access immediately. Eventually had to fast-track it and add the individuals to the People and Groups to keep the project going, but hoping not to have to maintain it that way. Any specific requirements of the security group in AD? Universal, Global, or domain local? Is there any time delay between modifying group members in AD and having that take effect in SharePoint?

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• question on reverse array

  - by davit-datuashvili

  we know algorithm how reverse array of n integers for (int i=0;i<n/2;i++){ swap(a[i],a[n-1-i]): } is this method better according the speed of algorithm or not because swap using xor is more fast then in other method here is code public class swap { public static void main(String[]args){ int a[]=new int[]{2,4,5,7,8,11,13,12,14,24}; System.out.println(" array at the begining:"); for (int i=0;i<a.length;i++){ System.out.println(a[i]); } for (int j=0;j<a.length/2;j++){ a[j]^=a[a.length-1-j]; a[a.length-1-j]^=a[j]; a[j]^=a[a.length-1-j]; } System.out.println("reversed array:"); for (int j=0;j<a.length;j++){ System.out.println(a[j]); } } } Result: array at the begining: 2 4 5 7 8 11 13 12 14 24 reversed array: 24 14 12 13 11 8 7 5 4 2

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• which is the cleaner way to do this simple while?

  - by user363834

  I'm learning c++ and I want to make clean and readable code and I was wondering which way is better (while is supposed to make the factorial of 9) : 1 - int main(){ int i = 1,r = i; while (i < 10) { r *= ++i; } 2 - int main(){ int i = 1,r = i; while (i < 10) { i++ r *= i } 1 may be harder to understand but it's 1 less line, is it worth it? and what about performance. Obviously it wouldn't matter in such a trivial example but it would be a good practice to make fast code from the begining.

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• slide navigation

  - by robosot

  I'm trying to make slide navigation. Here is my code html <li> <a href="#">Services</a> <div class="subcategories"> <a href="#">Cleaning</a> </div> </li> The subcategories div is hidden. js $('li a').hover(function() { $(this).next().slideToggle('fast', function() { }); }); This code works. The problem is that when the mouse goes out of the li a the subcategories div disappears. What i want is that when the user point the li a the subcategories div to be shown so the user be able to click on some link of the sub navigation.

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• Standardize word macro usage within the team

  - by user138010

  Hi, I have a team of 10 persons who work on word documents, they format them as per our defined guidlines. To complete the work fast we have created a macro that has been updated on all the machines. This macro corrects the font, size and formatting. How can I ensure and implement that nobody can change/replace or delete this macro from their system? In case this happens I should get an alert. Can something be done at the system or programme level? Thanks, PK

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• increasing speed and efficiency of ajax call

  - by user1048824

  I'm not the most disciplined dev, dont know standards and am self-taught so bear with me. I create stuff very logically and fast but not always using 'programming standards'. I have a mobile app using geolocation API. it gets thousands of places from my db and makes gmaps v3 markers for the ones around the user's current location. there is an ajax call from my JS to an aspx page that calls the database, makes a json string, and sends the json string to the javascript that then creates the google map markers. would i save time if the json string was in a flat file? im not sure if, generally speaking, accessing a sql db from an aspx page is faster than c# file i/o on a flat file with pre-rendered JSON. (of course, using the flat file, it would update everytime the db is updated)

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• What is most efficient way of setting row to zeros for a sparce scipy matrix?

  - by Alex Reinking

  I'm trying to convert the following MATLAB code to Python and am having trouble finding a solution that works in any reasonable amount of time. M = diag(sum(a)) - a; where = vertcat(in, out); M(where,:) = 0; M(where,where) = 1; Here, a is a sparse matrix and where is a vector (as are in/out). The solution I have using Python is: M = scipy.sparse.diags([degs], [0]) - A where = numpy.hstack((inVs, outVs)).astype(int) M = scipy.sparse.lil_matrix(M) M[where, :] = 0 # This is the slowest line M[where, where] = 1 M = scipy.sparse.csc_matrix(M) But since A is 334863x334863, this takes like three minutes. If anyone has any suggestions on how to make this faster, please contribute them! For comparison, MATLAB does this same step imperceptibly fast. Thanks!

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• Clarifying... So Background Jobs don't Tie Up Application Resources (in Rails)?

  - by viatropos

  I'm trying to get a better grasp of the inner workings of background jobs and how they improve performance. I understand that the goal is to have the application return a response to the user as fast as it can, so you don't want to, say, parse a huge feed that would take 10 seconds because it would prevent the application from being able to process any other requests. So it's recommended to put any operations that take more than say 500ms to execute, into a queued background job. What I don't understand is, doesn't that just delay the same problem? I know the user who invoked that background job will get an immediate response, but what if another user comes right when that background job starts (and it takes 10 seconds to finish), wont that user have to wait? Or is the main issue that, requests are the only thing that can happen one-at-a-time, while on the other hand a request can start while one+ background jobs are in the middle of running? Is that correct?

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• Iterators over a LInked List in a Game in Java

  - by Matthew

  I am using OpenGl in android and they have a callback method called draw that gets called with out my control. (As fast as the device can handle if I am not mistaken) I have a list of "GameObjects" that have a .draw method and a .update method. I have two different threads that handle each of those. So, the question is, can I declare two different iterators in two different methods in two different threads that iterate over the same Linked List? If so, do I simply declare ListIterator<GameObject> l = objets.listIterator() each time I want a new iterator and it won't interfere with other iterators?

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