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  • How to use parallel execution in a shell script?

    - by eSKay
    I have a C shell script that does something like this: #!/bin/csh gcc example.c -o ex gcc combine.c -o combine ex file1 r1 <-- 1 ex file2 r2 <-- 2 ex file3 r3 <-- 3 #... many more like the above combine r1 r2 r3 final \rm r1 r2 r3 Is there some way I can make lines 1, 2 and 3 run in parallel instead of one after the another?

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  • 3D effect to distort paper

    - by donpal
    This may be a little hard to describe since I don't have a sample. I'm trying to find a math function or full 3d function in php or a similar language that can help me with the following effect: imagine if you were to take a flat sheet or paper and glue it on a glass of water. It wouldn't be flat any more. It would have a curve, and one of its sides might end up being slightly hidden. Anyone can refer me to a good library or resource on the web where such functions can be found?

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  • How to Post Javascript to a MySQL Database

    - by salientanimal
    Hi guys, I have created a form in HTLM and I m trying to post the information in the form to a MySQL database. My form make suse of a dynamic list selection that needs to be captured to the database. However when submtting the form I get the following error Error: Unknown column 'coulmn_name' in 'field list'. Here is my HTML CODE for the form <td height="94"><p align="justify">CALL TRACKER - ADMIN</p></td> Customer Name : E-Mail Address : </tr> <tr> <td width="29%" align="right" valign="middle"><strong>Case Number :</strong></td> <td> <input type="text" name="case_number" width="70%" align="left" valign="middle"> </td> </tr> <tr> <td width="29%" align="right" valign="middle"><strong>MSISDN :</strong></td> <td> <input type="text" name="msisdn" width="70%" align="left" valign="middle"> </td> </tr> <tr> <td width="29%" align="right" valign="middle"> <strong>Route Cause :</strong></td> <td width="71%" align="left" valign="middle"> <select name="route_cause" id="category" onChange="javascript: listboxchange1(this.options[this.selectedIndex].value);"> <!-- <select name="route_cause" id="route_cause"> --> <option value="">Select the Call Reason</option> <option value="Billing Admin">Billing Admin</option> <option value="Customer Care">Customer Care</option> <option value="Insurance">Insurance</option> <option value="Repairs">Repairs</option> <option value="SIM Swap">SIM Swap</option> <option value="UTI">UTI</option> </select> </td> </tr> <tr> <td align="right" valign="middle"> <strong>Call Type/Indexed To :</strong></td> <td align="left" valign="middle"> <script type="text/javascript" language="javascript" name="calltype_indexedto"> <!-- document.write('<select name="subcategory1" onChange="javascript: listboxchange2(this.options[this.selectedIndex].value);"><option value=""></option></select>') --> </script> </td> </tr> <tr> <td align="right" valign="middle"> <strong>Type/TAT :</strong></td> <td align="left" valign="middle"> <script type="text/javascript" language="javascript" name="type_tat"> <!-- document.write('<select name="subcategory2" onChange="javascript: listboxchange3(this.options[this.selectedIndex].value);"><option value=""></option></select>') --> </script> </td> </tr> <tr> <td width="29%" align="right" valign="middle"> <strong>Escalated To :</strong></td> <td width="71%" align="left" valign="middle"> <select name="escalatedto" id="escalated_to"> <option value="">Select the Escalation</option> <option value="Billing Ops">Billing Ops</option> <option value="Resolvers">Resolvers</option> <option value="Finance">Finance</option> <option value="Ressolver">Ressolver</option> <option value="Nudebt">Nudebt</option> <option value="Transunion">Transunion</option> <option value="N/A">N/A</option> </select> </td> </tr> <tr> <td width="29%" align="right" valign="middle"> <strong>Requested By :</strong></td> <td width="71%" align="left" valign="middle"> <select name="requestedby" id="requested_by"> <option value="">UTI Requested By</option> <option value="Billing">Billing</option> <option value="Customer Service">Customer Service</option> <option value="Insurance">Insurance</option> <option value="Management">Management</option> <option value="Repairs">Repairs</option> <option value="Retail Support">Retail Support</option> <option value="Retentions">Retentions</option> <option value="SIM Swap">SIM Swap</option> <option value="WOW">WOW</option> <option value="N/A">N/A</option> </select> </td> </tr> <tr> <td width="29%" align="right" valign="middle"> <strong>Province :</strong></td> <td width="71%" align="left" valign="middle"> <select name="province" id="province"> <option value="">Select the Province</option> <option value="Eastern Cape">Eastern Cape</option> <option value="Gauteng">Gauteng</option> <option value="Kwa-Zulu Natal">Kwa-Zulu Natal</option> <option value="Limpopo">Limpopo</option> <option value="Mpumalanga">Mpumalanga</option> <option value="North West">North West</option> <option value="Northern Cape">Northern Cape</option> <option value="Polokwane">Polokwane</option> <option value="Western Cape">Western Cape</option> <option value="Other">Other</option> </select> </td> </tr> <tr> <td width="29%" align="right" valign="middle"><strong>Comments :</strong></td> <td> <textarea rows ="5" cols="30" name="comments"> </textarea> </td> </tr> <tr> <td> <p> <input type="reset" value="Reset Form"><input type="Submit" value="Submit"> Here is my PHP CODE to write to the Database <?php $con = mysql_connect("hostname" ,"mysqusername" ,"mysqlpassword"); if (!$con) { die('Could not connect: ' . mysql_error()); } mysql_select_db("databasename", $con); $sql="INSERT INTO customer_services_tracker (customer_name ,customer_email_address ,case_number ,msisdn ,route_cause ,calltype_indexedto ,type_tat ,escalatedto ,requestedby ,province ,comments ) VALUES ('$_POST[customer_name]' ,'$_POST[customer_email_address]' ,'$_POST[case_number]' ,'$_POST[msisdn]' ,'$_POST[route_cause]' ,'$_POST[calltype_indexedto]' ,'$_POST[type_tat]' ,'$_POST[escalatedto]' ,'$_POST[requestedby]' ,'$_POST[province]' ,'$_POST[comments]')"; $CatName = $rowCat["Name"]; if (!mysql_query($sql,$con)) { die('Error: ' . mysql_error()); } echo "1 record added"; mysql_close($con) ?>

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  • Matlab wont extract first row & column because of matrix dimensions !

    - by ZaZu
    Hey guys, I am tracking an object that is thrown in air, and this object governs a parabolic pattern. Im tracking the object through a series of 30 images. I managed to exclude all the background and keep the object apparent, then used its centroid to get its coordinates and plot them. Now im supposed to predict where the object is going to fall, so I used polyfit & polyval .. the problem is, matlab says ??? Index exceeds matrix dimensions. Now the centroid creates its own structure with a row and 2 columns. Everytime the object moves in the loop, it updates the first row only .. Here is part of the code : For N=1:30 . . . x=centroid(1,1); % extract first row and column for x y=centroid(1,2); % extract secnd row and column for x plot_xy=plot(x,y) set(plot_xy,'XData',x(1:N),'YData',y(1:N)); fitting=polyfit(x(1:N),y(1:N),2); parabola=plot(x,nan(23,1)); evaluate=polyval(fitting,x); set(parabola,'YData',evaluate) . . end The error message I get is ??? Index exceeds matrix dimensions. It seems that (1:N) is causing the problems .. I honestly do not know why .. But when I remove N, the object is plotted along with its points, but polyfitting wont work, it gives me an error saying : Warning: Polynomial is not unique; degree >= number of data points. > In polyfit at 72 If I made it (1:N-1) or something, it plots more points before it starts giving me the same error (not unique ...) . Any ideas why ?? Thanks alot !!

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  • Would this method work to scale out SQL queries?

    - by David
    I have a database containing a single huge table. At the moment a query can take anything from 10 to 20 minutes and I need that to go down to 10 seconds. I have spent months trying different products like GridSQL. GridSQL works fine, but is using its own parser which does not have all the needed features. I have also optimized my database in various ways without getting the speedup I need. I have a theory on how one could scale out queries, meaning that I utilize several nodes to run a single query in parallel. The idea is to take an incoming SQL query and simply run it exactly like it is on all the nodes. When the results are returned to a coordinator node, the same query is run on the union of the resultsets. I realize that an aggregate function like average need to be rewritten into a count and sum to the nodes and that the coordinator divides the sum of the sums with the sum of the counts to get the average. What kinds of problems could not easily be solved using this model. I believe one issue would be the count distinct function. Edit: I am getting so many nice suggestions, but none have addressed the method.

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  • minimum enclosing rectangle of fixed aspect ratio

    - by Ramya Narasimha
    I have an Image with many rectangles at different positions in the image and of different sizes (both overlapping and non-overlapping). I also have a non-negative scores associated with each of these rectangles. My problem now is to find one larger rectangle *of a fixed (given) aspect ratio* that encloses as many of these rectangles as possible. I am looking for an algorithm to do this, if anyone has a solution, even a partial one it would be helpful. Please note that the positions of the rectangles in the image is fixed and cannot be moved around and there is no orientation issue as all of them are upright.

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  • python multiprocess update dictionary synchronously

    - by user1050325
    I am trying to update one common dictionary through multiple processes. Could you please help me find out what is the problem with this code? I get the following output: inside function {1: 1, 2: -1} comes here inside function {1: 0, 2: 2} comes here {1: 0, 2: -1} Thanks. from multiprocessing import Lock, Process, Manager l= Lock() def computeCopyNum(test,val): l.acquire() test[val]=val print "inside function" print test l.release() return a=dict({1: 0, 2: -1}) procs=list() for i in range(1,3): p = Process(target=computeCopyNum, args=(a,i)) procs.append(p) p.start() for p in procs: p.join() print "comes here" print a

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  • Resize an array of images with OpenCV

    - by amr
    I'm passing an array of images (IplImage**) to an object in C++ using OpenCV. I'm then trying to iterate over that array and resize them all to a fixed size (150x150) I'm doing it this way: for(int i = 0; i< this->numTrainingFaces; i++) { IplImage* frame_copy = cvCreateImage( cvSize(150,150), this->faceImageArray[0]->depth, this->faceImageArray[0]->nChannels ); cout << "Created image" << endl; cvResize(this->faceImageArray[i], frame_copy); cout << "Resized image" << endl; IplImage* grey_image = cvCreateImage( cvSize( frame_copy->width, frame_copy->height ), IPL_DEPTH_8U, 1 ); cout << "Created grey image" << endl; cvCvtColor( frame_copy, grey_image, CV_RGB2GRAY ); cout << "Converted image" << endl; this->faceImageArray[i] = grey_image; cvReleaseImage(&frame_copy); cvReleaseImage(&grey_image); } But I'm getting this output, and I'm not sure why: Created image Resized image Created grey image Converted image Created image OpenCV Error: Assertion failed (src.type() == dst.type()) in cvResize, file /build/buildd/opencv-2.1.0/src/cv/cvimgwarp.cpp, line 3102 terminate called after throwing an instance of 'cv::Exception' what(): /build/buildd/opencv-2.1.0/src/cv/cvimgwarp.cpp:3102: error: (-215) src.type() == dst.type() in function cvResize Aborted I'm basically just trying to replace the image in the array with the resized one in as few steps as possible. Edit: Revised my code as follows: for(int i = 0; i< this->numTrainingFaces; i++) { IplImage* frame_copy = cvCreateImage( cvSize(150,150), this->faceImageArray[i]->depth, this->faceImageArray[i]->nChannels ); cvResize(this->faceImageArray[i], frame_copy); IplImage* grey_image = cvCreateImage( cvSize( frame_copy->width, frame_copy->height ), IPL_DEPTH_8U, 1 ); cvCvtColor( frame_copy, grey_image, CV_RGB2GRAY ); faceImageArray[i] = cvCreateImage( cvSize(grey_image->width, grey_image->height), grey_image->depth, grey_image->nChannels); cvCopy(grey_image,faceImageArray[i]); cvReleaseImage(&frame_copy); cvReleaseImage(&grey_image); } Then later on I'm performing some PCA, and get this output: OpenCV Error: Null pointer (Null pointer to the written object) in cvWrite, file /build/buildd/opencv-2.1.0/src/cxcore/cxpersistence.cpp, line 4740 But I don't think my code has got to the point where I'm explicitly calling cvWrite, so it must be part of the library. I can give a full implementation if necessary - is there anything in my code that's going to create a null pointer?

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  • Creating thumbnails PHP problem

    - by Wayne
    I have this source code where I got it from net tutsplus. I have configured it and made it work in one PHP file. It does work by transferring the original image, but it does not generate to the thumbnails folder. <?php $final_width_of_image = 100; $path_to_image_directory = "../../img/events/" . urldecode($_GET['name']) . "/"; $path_to_thumbs_directory = "../../img/events/" . urldecode($_GET['name']) . "/thumbnails/"; function createThumbnail($filename) { if(preg_match('/[.](jpg)$/', $filename)) { $im = imagecreatefromjpeg($path_to_image_directory . $filename); } elseif(preg_match('/[.](gif)$/', $filename)) { $im = imagecreatefromgif($path_to_image_directory . $filename); } elseif(preg_match('/[.](png)$/', $filename)) { $im = imagecreatefrompng($path_to_image_directory . $filename); } $ox = imagesx($im); $oy = imagesy($im); $nx = $final_width_of_image; $ny = floor($oy * ($final_width_of_image / $ox)); $nm = imagecreatetruecolor($nx, $ny); imagecopyresized($nm, $im, 0,0,0,0,$nx,$ny,$ox,$oy); imagejpeg($nm, $path_to_thumbs_directory . $filename); $tn = '<img src="' . $path_to_thumbs_directory . $filename . '" alt="image" />'; echo $tn; } if(isset($_FILES['fupload'])) { if(preg_match('/[.](jpg)|(gif)|(png)$/', $_FILES['fupload']['name'])) { $filename = $_FILES['fupload']['name']; $source = $_FILES['fupload']['tmp_name']; $target = $path_to_image_directory . $filename; move_uploaded_file($source, $target); createThumbnail($filename); } } ?> Basically it is supposed to generate a thumbnail of the uploaded image and store the original image into a different folder. The paths are correct, it works by getting the folder name in the URL, it does work, but nothing works for the thumbnails folder. BEFORE you ask this related question, yes, thumbnails generation does work on my server by the PHP GD, I have tested it separately. So this is not the problem. :) How do I get this to work? :(

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  • How do I use .NET to find an orange ball in an image?

    - by JohnS
    I'm getting images from a C328R camera attached to a small arduino robot. I want the robot to drive towards orange ping-pong balls and pick them up. I'm using the C# code supplied by funkotron76 at http://www.codeproject.com/KB/recipes/C328R.aspx. Is there a library I can use to do this, or do I need to iterate over every pixel in the image looking for orange? If so, what kind of tolerance would I need to compensate for various lighting conditions? I could probably test to figure out these numbers, but I'm hoping someone out there knows the answers.

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  • Image Resizing: Poor jpeg quality and black PNG backgrounds

    - by azz0r
    Hello, I have two issues with my class, basically the quality of the jpeg images is quite poor, but I'm not sure if thats down to my ratio resizing. Ideally I'd like this class to be strict with image sizes and crop into them, but I cant get my head around it. My main issue is that pngs always have a black bg, does anyone have experience with this happening? <?php class OpenSource_ImageResize { function __construct($theFile, $toWhere, $mime, $extension, $newWidth, $newHeight) { if ($mime == NULL) { $mime = getimagesize($theFile); $mime = $mime['mime']; } if ($mime == 'image/jpeg') { $size = getimagesize($theFile); if ($size[0] > $newWidth || $size[1] > $newHeight) { $sourceImage = imagecreatefromjpeg($theFile); } else { return copy($theFile, $toWhere); throw new exception('Could not create jpeg'); return false; } } else if ($mime == 'image/png') { $size = getimagesize($theFile); if ($size[0] > $newWidth || $size[1] > $newHeight) { $sourceImage = imagecreatefrompng($theFile); } else { return copy($theFile, $toWhere); //throw new exception('Could not create png'); return false; } } else if ($mime == 'image/gif') { $size = getimagesize($theFile); if ($size[0] > $newWidth || $size[1] > $newHeight) { $sourceImage = imagecreatefromgif ($theFile); } else { return copy($theFile, $toWhere); //throw new exception('Could not create gif'); return false; } } else { throw new exception('Not a valid mime type'); return false; } $oldX = imageSX($sourceImage); $oldY = imageSY($sourceImage); if ($newWidth == NULL) { $thumbHeight = $newHeight; $thumbWidth = round($newHeight/($oldY/$oldX)); } else if ($oldX > $oldY) { $thumbWidth = $newWidth; $thumbHeight = $oldY * ($newHeight/$oldX); } if ($oldX < $oldY) { $thumbWidth = round($newHeight/($oldY/$oldX)); $thumbHeight = $newHeight; } if ($oldX == $oldY) { $thumbWidth = $newWidth; $thumbHeight = $newHeight; } if (!gd_info()) { $dstImage = ImageCreate($thumbWidth, $thumbHeight); imagecopyresized($dstImage, $sourceImage, 0, 0, 0, 0, $thumbWidth, $thumbHeight, $oldX, $oldY); } else { $dstImage = ImageCreateTrueColor($thumbWidth, $thumbHeight); imagecopyresampled($dstImage, $sourceImage, 0, 0, 0, 0, $thumbWidth, $thumbHeight, $oldX, $oldY); } if ($mime == 'image/png') { $xparent = imagecolorresolvealpha($dstImage, 255,2,240, 0) ; imagecolortransparent($dstImage,$xparent); imagealphablending($dstImage,true); imagepng($dstImage, $toWhere); } else if ($mime == 'image/jpeg') { imagejpeg($dstImage, $toWhere); } else if ($mime == 'image/gif') { imagegif ($dstImage, $toWhere); } imagedestroy($dstImage); imagedestroy($sourceImage); return true; } }

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  • Resizing Images with ASP.NET and saving to Database

    - by Ryan
    I need to take an uploaded image, resize it, and save it to the database. Simple enough, except I don't have access to save any temp files to the server. I'm taking the image, resizing it as a Bitmap, and need to save it to a database field as the original image type (JPG for example). How can I get the FileBytes() like this, so I can save it to the database? Before I was using ImageUpload.FileBytes() but now that I'm resizing I'm dealing with Images and Bitmaps instead of FileUploads and can't seem find anything that will give me the bytes. Thanks!

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  • How would I detect horizontal-black lines using ImageMagick?

    - by Zando
    So I have what is essentially a spreadsheet in TIFF format. There is some uniformity to it...for example, all the column widths are the same. I want to de-limit this sheet by those known-column widths and basically create lots of little graphic files, one for each cell, and run OCR on them and store it into a database. The problem is that the horizontal lines are not all the same height, so I need to use some kind of graphics library command to check if every pixel across is the same color (i.e. black). And if so, then I know I've reached the height-delimiter for a cell. How would I go about doing that? (I'm using RMagick)

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  • radio button value in php

    - by Crash893
    Im trying to make a simple survey in php I have a set of radio buttons on a page called sja.php that sends its to sjamail.php page the problem is that when i go to get $answer = $_POST['ans']; I can't seen to do anything like echo "$answer"; but if i were to throw some logic at it like if ($answer == "ans1") { echo 'Correct'; } else { echo 'Incorrect'; } IT will display correct or incorrect so why is it i can't access the value of the radio button ans?

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  • PHP image resize and rounded image corners dynamically

    - by Dan
    I'm working of a script that dynamically ads rounded edges to an image then crops it down to a certain size. At the moment the script ads the rounded edges to the picture but i cannot get it so the original image is resized to fit within the dimensons of the final outputted image (140px x 120px) The problem is that the orginal uploaded image depending on it's orginal dimensions change the size it is in the final PNG { $image_file = $_FILES['image']['tmp_name']; $corner_radius = isset($_GET['radius']) ? $_GET['radius'] : 20; // The default corner radius is set to 20px $topleft = (isset($_GET['topleft']) and $_GET['topleft'] == "no") ? false : true; // Top-left rounded corner is shown by default $bottomleft = (isset($_GET['bottomleft']) and $_GET['bottomleft'] == "no") ? false : true; // Bottom-left rounded corner is shown by default $bottomright = (isset($_GET['bottomright']) and $_GET['bottomright'] == "no") ? false : true; // Bottom-right rounded corner is shown by default $topright = (isset($_GET['topright']) and $_GET['topright'] == "no") ? false : true; // Top-right rounded corner is shown by default $imagetype=$_FILES['image']['type']; $endsize=$corner_radius; $startsize=$endsize*3-1; $arcsize=$startsize*2+1; if (($imagetype=='image/jpeg') or ($imagetype=='jpg')) { $image = imagecreatefromjpeg($image_file); } else { if (($imagetype=='GIF') or ($imagetype=='gif')) { $image = imagecreatefromgif($image_file); } else { $image = imagecreatefrompng($image_file); } } $forecolor ='#ffffff'; $size = getimagesize($image_file); // Top-left corner $background = imagecreatetruecolor($size[0],$size[1]); imagecopymerge($background, $image, 0, 0, 0, 0, $size[0], $size[1], 100); $startx=$size[0]*2-1; $starty=$size[1]*2-1; $im_temp = imagecreatetruecolor($startx,$starty); imagecopyresampled($im_temp, $background, 0, 0, 0, 0, $startx, $starty, $size[0], $size[1]); $bg = imagecolorallocate($im_temp, 255,255,255); $fg = imagecolorallocate($im_temp, 255,255,255); if ($topleft == true) { if(!imagearc($im_temp, $startsize, $startsize, $arcsize, $arcsize, 180,270,$bg))echo "nope"; imagefilltoborder($im_temp,0,0,$bg,$bg); } // Bottom-left corner // Top-right corner if ($topright == true) { imagearc($im_temp, $startx-$startsize, $startsize,$arcsize, $arcsize, 270,360,$bg); imagefilltoborder($im_temp,$startx,0,$bg,$bg); } $image = imagecreatetruecolor(140,120); imagecopyresampled($image, $im_temp, 0, 0, 0, 0, $size[0],$size[1],$starty+1310,$startx+1500); // Output final image if(!imagepng($image,'hello.png')) echo "boo"; if(!imagedestroy($image)) echo "2"; if(!imagedestroy($background)) echo "3"; if(!imagedestroy($im_temp)) echo "4"; } EDIT: My question is how to get the orginal image reized so it fits into the 140 x 120 image that is processed with the rounded edges?

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  • parallel computation for an Iterator of elements in Java

    - by Brian Harris
    I've had the same need a few times now and wanted to get other thoughts on the right way to structure a solution. The need is to perform some operation on many elements on many threads without needing to have all elements in memory at once, just the ones under computation. As in, Iterables.partition is insufficient because it brings all elements into memory up front. Expressing it in code, I want to write a BulkCalc2 that does the same thing as BulkCalc1, just in parallel. Below is sample code that illustrates my best attempt. I'm not satisfied because it's big and ugly, but it does seem to accomplish my goals of keeping threads highly utilized until the work is done, propagating any exceptions during computation, and not having more than numThreads instances of BigThing necessarily in memory at once. I'll accept the answer which meets the stated goals in the most concise way, whether it's a way to improve my BulkCalc2 or a completely different solution. interface BigThing { int getId(); String getString(); } class Calc { // somewhat expensive computation double calc(BigThing bigThing) { Random r = new Random(bigThing.getString().hashCode()); double d = 0; for (int i = 0; i < 100000; i++) { d += r.nextDouble(); } return d; } } class BulkCalc1 { final Calc calc; public BulkCalc1(Calc calc) { this.calc = calc; } public TreeMap<Integer, Double> calc(Iterator<BigThing> in) { TreeMap<Integer, Double> results = Maps.newTreeMap(); while (in.hasNext()) { BigThing o = in.next(); results.put(o.getId(), calc.calc(o)); } return results; } } class SafeIterator<T> { final Iterator<T> in; SafeIterator(Iterator<T> in) { this.in = in; } synchronized T nextOrNull() { if (in.hasNext()) { return in.next(); } return null; } } class BulkCalc2 { final Calc calc; final int numThreads; public BulkCalc2(Calc calc, int numThreads) { this.calc = calc; this.numThreads = numThreads; } public TreeMap<Integer, Double> calc(Iterator<BigThing> in) { ExecutorService e = Executors.newFixedThreadPool(numThreads); List<Future<?>> futures = Lists.newLinkedList(); final Map<Integer, Double> results = new MapMaker().concurrencyLevel(numThreads).makeMap(); final SafeIterator<BigThing> it = new SafeIterator<BigThing>(in); for (int i = 0; i < numThreads; i++) { futures.add(e.submit(new Runnable() { @Override public void run() { while (true) { BigThing o = it.nextOrNull(); if (o == null) { return; } results.put(o.getId(), calc.calc(o)); } } })); } e.shutdown(); for (Future<?> future : futures) { try { future.get(); } catch (InterruptedException ex) { // swallowing is OK } catch (ExecutionException ex) { throw Throwables.propagate(ex.getCause()); } } return new TreeMap<Integer, Double>(results); } }

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  • problem with background subtraction

    - by riyana
    I'm doing background subtraction using opencv. The problem is the foreground object is not always detected correctly. To deal with this I would like to use four or five images, and take their average as the background image. How can I do that?

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  • What is the "task" in twitter Storm parallelism

    - by John Wang
    I'm trying to learn twitter storm by following the great article "Understanding the parallelism of a Storm topology" However I'm a bit confused by the concept of "task". Is a task an running instance of the component(spout or bolt) ? A executor having multiple tasks actually is saying the same component is executed for multiple times by the executor, am I correct ? Moreover in a general parallelism sense, Storm will spawn a dedicated thread(executor) for a spout or bolt, but what is contributed to the parallelism by an executor(thread) having multiple tasks ? I think having multiple tasks in a thread, since a thread executes sequentially, only make the thread a kind of "cached" resource, which avoids spawning new thread for next task run. Am I correct? I may clear those confusion by myself after taking more time to investigate, but you know, we both love stackoverflow ;-) Thanks in advance.

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  • Parallel version of loop not faster than serial version

    - by Il-Bhima
    I'm writing a program in C++ to perform a simulation of particular system. For each timestep, the biggest part of the execution is taking up by a single loop. Fortunately this is embarassingly parallel, so I decided to use Boost Threads to parallelize it (I'm running on a 2 core machine). I would expect at speedup close to 2 times the serial version, since there is no locking. However I am finding that there is no speedup at all. I implemented the parallel version of the loop as follows: Wake up the two threads (they are blocked on a barrier). Each thread then performs the following: Atomically fetch and increment a global counter. Retrieve the particle with that index. Perform the computation on that particle, storing the result in a separate array Wait on a job finished barrier The main thread waits on the job finished barrier. I used this approach since it should provide good load balancing (since each computation may take differing amounts of time). I am really curious as to what could possibly cause this slowdown. I always read that atomic variables are fast, but now I'm starting to wonder whether they have their performance costs. If anybody has some ideas what to look for or any hints I would really appreciate it. I've been bashing my head on it for a week, and profiling has not revealed much.

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  • Generate an image / thumbnail of a webpage using X/Gui-less linux

    - by dassouki
    There are a lot of solutions out there on generating a thumbnail or an image preview of a webpage. Some of these are websites like websnapshots, windows libraries such as PHP's imagegrabscreen (only works on windows), and KDE's wkhtml. Many more do exist. However, I'm looking for a GUI-less solution. Something I can create an API around and link it to php or python. I'm comfortable with python, php, C, and shell. This is a personal project, so I'm not interested in commercial applications as I'm aware of their existence. Any ideas?

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