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  • question on revrse 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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  • Writing a custom wpf 'rolling' plot control (are there any components with such functionality?)

    - by adrin
    I need a wpf plot control that would 'roll' (scroll) as data is fed to it (instead of stretching, etc). Unfortunately i didnt find a working component so now I am considering writing my own control (its plotting features need to be simple). Did anyone write a custom plot/chart control? Is it difficult? What container should I use (Canvas & ViewBox?) so that it is reasonably fast, easy to write and scales as window is resized?

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  • Example applications and benefits of using "C" , "C++" or "Java"

    - by Waltzy
    Ok, I'm revising for my upcoming year 2 exams on a CS course and its likely something like this will come up. my question is what is an ideal application that would especially benefit from the program features of each of the three languages? I have a vague idea but getting a second opinion could really help. JavaPortability, easy - good for GUIs. C++Fast but may requite significant changes in order to be moved from system to system, good for image processing. CI'm unsure here small embedded applications? Some clarification on this would be really appreciated, thanks again StackOverflow

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  • The largest prime factor with php

    - by Tom
    So, I wrote php program to find the largest prime factor with php and I think it is quite optimal, because it loads quite fast. But there is a problem, it doesn't count very big numbers's prime factors. Here is a program: function is_even($s) { $sk_sum = 0; for($i = 1; $i <= $s; $i++) { if($s % $i == 0) { $sk_sum++; } } if($sk_sum == 2) { return true; } } $x = 600851475143; $i = 2; //x is number while($i <= $x) { if($x % $i == 0) { if(is_even($i)) { $sk = $i; $x = $x / $i; } } $i++; } echo $sk;

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  • Maximum length of a std::basic_string<_CharT> string

    - by themoondothshine
    Hey all, I was wondering how one can fix an upper limit for the length of a string (in C++) for a given platform. I scrutinized a lot of libraries, and most of them define it arbitrarily. The GNU C++ STL (the one with experimental C++0x features) has quite a definition: size_t npos = size_t(-1); /*!< The maximum value that can be stored in a variable of type size_t */ size_t _S_max_len = ((npos - sizeof(_Rep_base))/sizeof(_CharT) - 1) / 4; /*!< Where _CharT is a template parameter; _Rep_base is a structure which encapsulates the allocated memory */ Here's how I understand the formula: The size_t type must hold the count of units allocated to the string (where each unit is of type _CharT) Theoretically, the maximum value that a variable of type size_t can take on is the total number of units of 1 byte (ie, of type char) that may be allocated The previous value minus the overhead required to keep track of the allocated memory (_Rep_base) is therefore the maximum number of units in a string. Divide this value by sizeof(_CharT) as _CharT may require more than a byte Subtract 1 from the previous value to account for a terminating character Finally, that leave the division by 4. I have absolutely no idea why! I looked at a lot of places for an explanation, but couldn't find a satisfactory one anywhere (that's why I've been trying to make up something for it! Please correct me if I'm wrong!!).

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  • jQuery .click() .toggle() - change display and swap character

    - by danit
    Here is my jQuery: $('.ask').click(function() { $('.addtitle').slideToggle('fast', function() { // Animation complete. }); }); And my HTML: <p class="ask">+</p> <div class="addtitle"> <p>Give your Idea a great title</p> <form name="input" action="#" method="get"> <input id="title" type="text" name="title" /> <input id="go" type="submit" value="Go" /> </form> </div> I have multiple .ask div's on the page and I only want it to effect the .next() div named .ask rather than all div's named .ask. I also want to .toggle() the '+' character to '-' Can anyone assist?

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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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  • Jquery image slider window resize scaling issue

    - by eb_Dev
    Hi, I have created image gallery slider, the images of which scale with the window size. My problem is I can't seem to create the right formula to ensure that the slider is at the right position when the window is scaled. If I am at the first image and the slider 'left' offset is 0 then the scaling works fine and my offset is correct, however when I am on image two and my slider is offset by say -1500 and then the window is resized, the slider is then at the wrong offset. Taking this into account I figured I could just add / subtract the new window size difference from the slider offset and therefore have everything in the right position. I was wrong. It works for the first two images but then If I am at the end of my slider on the last image I get a nice big gap between the end of the last image and the border of the page. Can someone please show my where I am going wrong please? I've spent days on this :( The relevant code is as follows: $(window).bind('resize', function(event, delta) { /* Resize work images - resizes all to document width */ resizeWorkImages('div.page.work div#work ul'); /* Position slider controls */ positionSliderControls(); /* Get the difference between the old window width and the new */ var windowDiff = (gLastWindowWidth - $(window).width()) * -1; /* Apply difference to slider left position */ var newSliderLeftPos = stripPx($('div.page.work div#work ul').css('left')) - windowDiff; /* Apply to slider */ $('div.page.work div#work ul').css('left',newSliderLeftPos+'px') /* Update gSlider settings */ gSlider.update(); /* Record new window width */ gLastWindowWidth = $(window).width(); }); Thanks, eb_dev

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • determining the starting speed for an accelerated animation (in flash/actionscript but it's a math question)

    - by vulkanino
    This question burns my brain. I have an object on a plane, but for the sake of simplicity let's work just on a single dimension, thus the object has a starting position xs. I know the ending position xe. The object has to move from starting to ending position with an accelerated (acceleration=a) movement. I know the velocity the object has to have at the ending position (=ve). In my special case the ending speed is zero, but of course I need a general formula. The only unknown is the starting velocity vs. The objects starts with vs in xs and ends with ve in xe, moving along a space x with an acceleration a in a time t. Since I'm working with flash, space is expressed in pixels, time is expressed in frames (but you can reason in terms of seconds, it's easy to convert knowing the frames-per-second). In the animation loop (think onEnterFrame) I compute the new velocity and the new position with (a=0.4 for example): vx *= a (same for vy) x += vx (same for y) I want the entire animation to last, say, 2 seconds, which at 30 fps is 60 frames. Now you know that in 60 frames my object has to move from xs to xe with a constant deceleration so that the ending speed is 0. How do I compute the starting speed vs? Maybe there's a simpler way to do this in Flash, but I am now interested in the math/physics behind this.

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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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  • 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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  • 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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  • 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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  • 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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  • 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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