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  • What hash algorithms are parallelizable? Optimizing the hashing of large files utilizing on multi-co

    - by DanO
    I'm interested in optimizing the hashing of some large files (optimizing wall clock time). The I/O has been optimized well enough already and the I/O device (local SSD) is only tapped at about 25% of capacity, while one of the CPU cores is completely maxed-out. I have more cores available, and in the future will likely have even more cores. So far I've only been able to tap into more cores if I happen to need multiple hashes of the same file, say an MD5 AND a SHA256 at the same time. I can use the same I/O stream to feed two or more hash algorithms, and I get the faster algorithms done for free (as far as wall clock time). As I understand most hash algorithms, each new bit changes the entire result, and it is inherently challenging/impossible to do in parallel. Are any of the mainstream hash algorithms parallelizable? Are there any non-mainstream hashes that are parallelizable (and that have at least a sample implementation available)? As future CPUs will trend toward more cores and a leveling off in clock speed, is there any way to improve the performance of file hashing? (other than liquid nitrogen cooled overclocking?) or is it inherently non-parallelizable?

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  • How can i connect two or more machines via tcp cable to form a network grid?

    - by Gath
    How can i connect two or more machines to form a network grid and how can i distribute work load to the two machines? What operating systems do i need to run on the machines, and what application should i use to manage the load balancing? NB: I read somewhere that google uses cheap machines to perform this fete, how do they connect two network cards( 'Teaming' ) and distribute load across the machines? Good practical examples would serve me good, with actual code samples. Pointers to some good site i might read this stuff will be highly appreciated.

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  • Executing functions parallelly in PHP

    - by binaryLV
    Hi! Can PHP call a function and don't wait for it to return? So something like this: function callback($pause, $arg) { sleep($pause); echo $arg, "\n"; } header('Content-Type: text/plain'); fast_call_user_func_array('callback', array(3, 'three')); fast_call_user_func_array('callback', array(2, 'two')); fast_call_user_func_array('callback', array(1, 'one')); would output one (after 1 second) two (after 2 seconds) three (after 3 seconds) rather than three (after 3 seconds) two (after 3 + 2 = 5 seconds) one (after 3 + 2 + 1 = 6 seconds) Main script is intended to be run as a permanent process (TCP server). callback() function would receive data from client, execute external PHP script and then do something based on other arguments that are passed to callback(). The problem is that main script must not wait for external PHP script to finish. Result of external script is important, so exec('php -f file.php &') is not an option.

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  • SQL query to select distinct record with 2 or more repetition in another field

    - by kyohiros
    So I have this table of book orders, it contains 2 columns, one is the order ID(primary key) and another is the ID of the book that the customer ordered. For example: | OrderID | BookID | | 0001 | B002 | | 0002 | B005 | | 0003 | B002 | | 0004 | B003 | | 0005 | B005 | | 0006 | B002 | | 0007 | B002 | What I want is to get the IDs of the books that got 2 or more purchases/orders, for example if I run the SQL query against the above data, I would get this as the result: | BookID | | B002 | | B005 | I don't know if this can be archived in SQL or I have to built a simpler statement and repetitive run the query against all the records in another language. I need some help and thanks for reading my question.

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  • MD5 and Hibernate Query

    - by theJava
    public Login authenticate(Login login) { String query = "SELECT L FROM Login AS L WHERE L.email=? AND L.password=?"; Object[] parameters = { login.getEmail(), login.getPassword() }; List<Login> resultsList = (getHibernateTemplate().find(query,parameters)); if (resultsList.isEmpty()) { //error dude } else if (resultsList.size() > 1) { //throw expections } else { Login login1 = (Login) resultsList.get(0); return login1; } return null; } I have my DB tables password col set as MD5, now how to retrieve it back here.

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  • How to convert a BufferedImage to 8 bit?

    - by Zach Sugano
    I was looking at the ImageConverter class, trying to figure out how to convert a BufferedImage to 8-bit color, but I have no idea how I would do this. I was also searching around the internet and I could find no simple answer, they were all talking about 8 bit grayscale images. I simply want to convert the colors of an image to 8 bit... nothing else, no resizing no nothing. Does anyone mind telling me how to do this.

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  • efficient video format/codec for sparse & binary blob tracking

    - by user391339
    I am working on a blob tracking project and have many high-definition videos that I would like to reduce in size for storage and downstream tracking/shape-analysis. I want to use a lossless method that takes advantage of the black and white nature of the video as well as the fact that not much is moving between individual frames. The videos are quite sparse, with 5 to 10 b&w blobs per frame occupying <30% of the space in total, with each blob moving <5-10% of the field of view between frames and not changing shape too much between 2-3 frames. I will work in Python, Matlab, or LabView for this project, and could use a batch utility if available. It may be worthwhile to export the files as compressed image stacks if a proper video format can't be found. What are the pros and cons of this? A video codec uses correlations between neighboring frames, so it should be more efficient, but not if the wrong one is chosen or if it is improperly configured.

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  • using Hibernate to loading 20K products, modifying the entity and updating to db

    - by Blankman
    I am using hibernate to update 20K products in my database. As of now I am pulling in the 20K products, looping through them and modifying some properties and then updating the database. so: load products foreach products session begintransaction productDao.MakePersistant(p); session commit(); As of now things are pretty slow compared to your standard jdbc, what can I do to speed things up? I am sure I am doing something wrong here.

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  • CouchDB Lucene How to URL Encode Query containing Minus (-)

    - by Peter
    I'd like to query text containing a minus (-) Sign, e.g. foo-bar with a couchdb lucene fulltext query. Following lucene rules I'd have to escape the minus, resulting in foo\-bar Last I'd have to urlencode the backslash resulting in foo%5C-bar So the complete url would be: http://127.0.0.1:5984/_fti/local/db/_design/foo/by_subject?q=foo%5C-bar Neither works. The result is always split in two phrases "q":"default:foo default:bar" Leading to documents containing only foo or bar being found also. Thanks for your help!

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  • Why are Asynchronous processes not called Synchronous?

    - by Balk
    So I'm a little confused by this terminology. Everyone refers to "Asynchronous" computing as running different processes on seperate threads, which gives the illusion that these processes are running at the same time. This is not the definition of the word asynchronous. a·syn·chro·nous –adjective 1. not occurring at the same time. 2. (of a computer or other electrical machine) having each operation started only after the preceding operation is completed. What am I not understanding here?

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  • Why some pictures are are crooked aftes using my function?

    - by Miko Kronn
    struct BitmapDataAccessor { private readonly byte[] data; private readonly int[] rowStarts; public readonly int Height; public readonly int Width; public BitmapDataAccessor(byte[] data, int width, int height) { this.data = data; this.Height = height; this.Width = width; rowStarts = new int[height]; for (int y = 0; y < Height; y++) rowStarts[y] = y * width; } public byte this[int x, int y, int color] // Maybe use an enum with Red = 0, Green = 1, and Blue = 2 members? { get { return data[(rowStarts[y] + x) * 3 + color]; } set { data[(rowStarts[y] + x) * 3 + color] = value; } } public byte[] Data { get { return data; } } } public static byte[, ,] Bitmap2Byte(Bitmap obraz) { int h = obraz.Height; int w = obraz.Width; byte[, ,] wynik = new byte[w, h, 3]; BitmapData bd = obraz.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb); int bytes = Math.Abs(bd.Stride) * h; byte[] rgbValues = new byte[bytes]; IntPtr ptr = bd.Scan0; System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes); BitmapDataAccessor bda = new BitmapDataAccessor(rgbValues, w, h); for (int i = 0; i < h; i++) { for (int j = 0; j < w; j++) { wynik[j, i, 0] = bda[j, i, 2]; wynik[j, i, 1] = bda[j, i, 1]; wynik[j, i, 2] = bda[j, i, 0]; } } obraz.UnlockBits(bd); return wynik; } public static Bitmap Byte2Bitmap(byte[, ,] tablica) { if (tablica.GetLength(2) != 3) { throw new NieprawidlowyWymiarTablicyException(); } int w = tablica.GetLength(0); int h = tablica.GetLength(1); Bitmap obraz = new Bitmap(w, h, PixelFormat.Format24bppRgb); for (int i = 0; i < w; i++) { for (int j = 0; j < h; j++) { Color kol = Color.FromArgb(tablica[i, j, 0], tablica[i, j, 1], tablica[i, j, 2]); obraz.SetPixel(i, j, kol); } } return obraz; } Now, if I do: private void btnLoad_Click(object sender, EventArgs e) { if (dgOpenFile.ShowDialog() == DialogResult.OK) { try { Bitmap img = new Bitmap(dgOpenFile.FileName); byte[, ,] tab = Grafika.Bitmap2Byte(img); picture.Image = Grafika.Byte2Bitmap(tab); picture.Size = img.Size; } catch (Exception ex) { MessageBox.Show(ex.Message); } } } Most of pictures are handled correctly butsome not. Example of picture that doesn't work: It produce following result (this is only fragment of picture) : Why is that?

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  • Action T synchronous and asynchronous

    - by raffaeu
    Hi everybody I have a contextmenustrip control that allows you to execute an action is two different flawours. Sync and Async. I am trying to covert everything using Generics so I did this: public class BaseContextMenu<T> : IContextMenu { private T executor ... public void Exec(Action<T> action){ action.Invoke(this.executor); } public void ExecAsync(Action<T> asyncAction){ ... } How I can write the async method in order to execute the generic action and 'do something' with the menu in the meanwhile? I saw that the signature of BeginInvoke is something like: asyncAction.BeginInvoke(thi.executor, IAsyncCallback, object);

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  • Python: How to extract xml embedded in a html file?

    - by georgehu
    I have a html file with xml snipped embedded, the source code is pasted in the pastbin: http://pastebin.com/Hy0QaWk8 my task is to extract the text enclosed in the first textarea, which is a xml snippet, from the html. Without any change to the original snippet. I'm able to get it by using the BeautifulSoup, but it changes all the tag names into lower case.

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  • C++: FFMPEG and SDL resources

    - by advs89
    I'm looking for resources (preferably books, but websites are fine too) for using FFMPEG and/or SDL with C++. Stuff I'd like to be able to do (eventually): Decode and play videos in realtime to a QT widget (the QT part isn't a problem) Overlay text and images on the video (in realtime) Loop video Cross-fade from one video to another (in realtime) Some kind of DVD functionality LIVE sources? (i.e. webcam, stream, etc.) So far I've looked at (and consider helpful) the following resources: FFMPEG and SDL Tutorial by Dranger (extremely helpful) StackOverflow: ffmpeg C API documentation/tutorial (not a duplicate, btw) Sample code bundled with FFMPEG libraries (I'll try and update this list with anything helpful below) Thanks for any help... Also: Operating System is Windows (but maybe one day cross-platform) Also 2: Resources using alternatives are welcome too... i.e. DirectShow, VFW, etc.

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  • Which library should I use for server-side image manipulation on Node.JS?

    - by Andrew
    I found a quite large list of available libraries on Node.JS wiki but I'm not sure which of those are more mature and provide better performance. Basically I want to do the following: load some images to a server from external sources put them onto one big canvas crop and mask them a bit apply a filter or two Resize the final image and give a link to it Big plus if the node package works on both Linux and Windows.

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  • Thumbnail image saved with worse quality on Windows Server 2003

    - by Angelo
    Hello, In asp.net 2.0 application I am trying to create thumbnails from uploaded images. However when I test the application on my PC under Windows7 it works fine, but on the real Windows 2003 Server the resized image has worse quality. Where this difference could come from? Different JPEG codec or what, if Yes how it can be updated on Win 2003 Server? Thanks! Here is the code: Resize of the Image: Bitmap newBmp = new Bitmap(imgWidth, imgHeight, PixelFormat.Format24bppRgb); newBmp.SetResolution(inputBmp.HorizontalResolution, inputBmp.VerticalResolution); //Create a graphics object attached to the new bitmap Graphics newBmpGraphics = Graphics.FromImage(newBmp); newBmpGraphics.InterpolationMode = InterpolationMode.HighQualityBicubic; newBmpGraphics.SmoothingMode = SmoothingMode.HighQuality; newBmpGraphics.PixelOffsetMode = PixelOffsetMode.HighQuality; newBmpGraphics.DrawImage(inputBmp, new Rectangle(0, 0, imgWidth, imgHeight), new Rectangle(0, 0, inputBmp.Width, inputBmp.Height), GraphicsUnit.Pixel); Save of the Image: System.IO.Stream imgStream = new System.IO.MemoryStream(); //Get the ImageCodecInfo for the desired target format ImageCodecInfo destCodec = FindCodecForType(ImageMimeTypes.JPEG); if (destCodec == null) { //No codec available for that format throw new ArgumentException("The requested format image/jpeg does not have an available codec installed", "destFormat"); } //Create an EncoderParameters collection to contain the //parameters that control the dest format's encoder EncoderParameters destEncParams = new EncoderParameters(1); EncoderParameter qualityParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality,(long)quality); destEncParams.Param[0] = qualityParam; //Save w/ the selected codec and encoder parameters inputBmp.Save(imgStream, destCodec, destEncParams); Bitmap destBitmap = new Bitmap(imgStream);

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  • how can i substitute a NULL value for a 0 in an SQL Query result

    - by Name.IsNullOrEmpty
    SELECT EmployeeMaster.EmpNo, Sum(LeaveApplications.LeaveDaysTaken) AS LeaveDays FROM EmployeeMaster FULL OUTER JOIN LeaveApplications ON EmployeeMaster.id = LeaveApplications.EmployeeRecordID INNER JOIN LeaveMaster ON EmployeeMaster.id = LeaveMaster.EmpRecordID GRoup BY EmployeeMaster.EmpNo order by LeaveDays Desc with the above query, if an employee has no leave application record in table LeaveApplications, then their Sum(LeaveApplications.LeaveDaysTaken) AS LeaveDays column returns NULL. What i would like to do is place a value of 0 (Zero) instead of NULL. I want to do this because i have a calculated column in the same query whose formular depends on the LeaveDays returned and when LeaveDays is NULL, the formular some how fails. Is there away i can put 0 for NULL such that that i can get my desired result.

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  • How do I prevent ImageMagick convert from scaling images *up*?

    - by Kyle
    I'm using ImageMagick's convert tool to generate image thumbnails for a web application. I'm using notation like so: 600x600> The images are indeed scaled to 600px wide/tall (depending on the longer side) and proportions are properly maintained, however images less than 600px in either direction are scaled up — this behavior is not desired. Is there a way to prevent convert from scaling images up if the destination dimensions both exceed the original image size?

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