1 2 3 4 5<!doctype html> 6<html lang="en"> 7<head> 8 <meta charset="utf-8" /> 9 <meta name="viewport" content="width=device-width, initial-scale=1" /> 10 <title>ImageMagick - Parallel Execution with OpenMP</title> 11 <meta name="application-name" content="ImageMagick" /> 12 <meta name="description" content="Use ImageMagick® to create, edit, compose, and convert digital images. Resize an image, crop it, change its shades and colors, add captions, and more." /> 13 <meta name="application-url" content="https://imagemagick.org" /> 14 <meta name="generator" content="PHP" /> 15 <meta name="keywords" content="parallel, execution, with, openmp, image processing software" /> 16 <meta name="rating" content="GENERAL" /> 17 <meta name="robots" content="INDEX, FOLLOW" /> 18 <meta name="generator" content="ImageMagick Studio LLC" /> 19 <meta name="author" content="ImageMagick Studio LLC" /> 20 <meta name="revisit-after" content="2 DAYS" /> 21 <meta name="resource-type" content="document" /> 22 <meta name="copyright" content="Copyright (c) 1999-2020 ImageMagick Studio LLC" /> 23 <meta name="distribution" content="Global" /> 24 <meta name="magick-serial" content="P131-S030410-R485315270133-P82224-A6668-G1245-1" /> 25 <meta property='og:url' content='../' /> 26 <meta property='og:title' content='ImageMagick' /> 27 <meta property='og:image' content='../images/logo.png' /> 28 <meta property='og:type' content='website' /> 29 <meta property='og:site_name' content='ImageMagick' /> 30 <meta property='og:description' content="Create, Edit, Compose, or Convert Digital Images" /> 31 <meta name="google-site-verification" content="_bMOCDpkx9ZAzBwb2kF3PRHbfUUdFj2uO8Jd1AXArz4" /> 32 <link href="openmp.html" rel="canonical" /> 33 <link href="../images/wand.png" rel="icon" /> 34 <link href="../images/wand.ico" rel="shortcut icon" /> 35 <link href="assets/magick.css" rel="stylesheet" /> 36</head> 37<body> 38 <nav class="navbar navbar-expand-md navbar-dark bg-dark fixed-top"> 39 <div class="container-fluid"> 40 <a class="navbar-brand" href="../"><img class="d-block" id="icon" alt="ImageMagick" width="32" height="32" src="../images/wand.ico"/></a> 41 <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#magick-navbars" aria-controls="magick-navbars" aria-expanded="false" aria-label="Toggle navigation"> 42 <span class="navbar-toggler-icon"></span> 43 </button> 44 45 <div class="collapse navbar-collapse" id="magick-navbars"> 46 <ul class="navbar-nav me-auto mb-2 mb-md-0"> 47 <li class="nav-item"> 48 <a class="nav-link " href="../www/index.html">Home</a> 49 </li> 50 <li class="nav-item"> 51 <a class="nav-link " href="../www/download.html">Download</a> 52 </li> 53 <li class="nav-item"> 54 <a class="nav-link " href="../www/command-line-tools.html">Tools</a> 55 </li> 56 <li class="nav-item"> 57 <a class="nav-link " href="../www/command-line-processing.html">CLI</a> 58 </li> 59 <li class="nav-item"> 60 <a class="nav-link " href="../www/develop.html">Develop</a> 61 </li> 62 <li class="nav-item"> 63 <a class="nav-link" target="_blank" href="https://github.com/ImageMagick/ImageMagick/discussions">Community</a> 64 </li> 65 <li class="nav-item"> 66 <iframe src="https://github.com/sponsors/ImageMagick/button" title="Sponsor ImageMagick" height="35" width="107" style="border: 0;"></iframe> 67 </li> 68 </ul> 69 <form class="d-flex form-inline" action="search.html"> 70 <input class="form-control me-2" type="text" name="q" placeholder="Search" aria-label="Search"> 71 <button class="btn btn-outline-success" type="submit" name="sa">Search</button> 72 </form> 73 </div> 74 </div> 75 </nav> 76 77 <div class="container"> 78 <script async="async" src="https://localhost/pagead/js/adsbygoogle.js"></script> 79 <ins class="adsbygoogle" 80 style="display:block" 81 data-ad-client="ca-pub-3129977114552745" 82 data-ad-slot="6345125851" 83 data-full-width-responsive="true" 84 data-ad-format="horizontal"></ins> 85 <script> 86 (adsbygoogle = window.adsbygoogle || []).push({}); 87 </script> 88 89 </div> 90 91 <main class="container"> 92 <div class="magick-template"> 93<div class="magick-header"> 94<h1 class="text-center">Threads of Execution</h1> 95<p class="lead magick-description">Many of ImageMagick's internal algorithms are threaded to take advantage of speed-ups offered by the multicore processor chips and <a href="http://www.openmp.org">OpenMP</a>. OpenMP, is an API specification for parallel programming. If your compiler supports OpenMP (e.g. gcc, Visual Studio 2005) directives, ImageMagick automatically includes support. To verify, look for the OpenMP feature of ImageMagick with this command:</p> 96<pre class="highlight"><code>-> magick identify -version 97Version: ImageMagick 7.0.10-50 2021-01-04 Q16 https://imagemagick.org 98Copyright: © 1999-2021 ImageMagick Studio LLC 99Features: OpenMP(4.5)</code></pre> 100<p>With OpenMP enabled, most ImageMagick algorithms execute on all the cores on your system in parallel. ImageMagick typically divides the work so that each thread processes 64 rows of pixels. As rows are completed, OpenMP assigns more chunks of pixel rows to each thread until the algorithm completes. For example, if you have a quad-core system, and attempt to resize an image, the resizing takes place on 4 cores (8 if hyperthreading is enabled).</p> 101<p>You can further increase performance by reducing lock contention with the <a href="http://goog-perftools.sourceforge.net/doc/tcmalloc.html">tcmalloc</a> memory allocation library. To enable, add <code>--with-tcmalloc</code> to the <code>configure</code> command-line when you build ImageMagick.</p> 102<h5>The Perils of Parallel Execution</h5> 103<p>It can be difficult to predict behavior in a parallel environment. Performance might depend on a number of factors including the compiler, the version of the OpenMP library, the processor type, the number of cores, the amount of memory, whether hyperthreading is enabled, the mix of applications that are executing concurrently with ImageMagick, or the particular image-processing algorithm you utilize. The only way to be certain of the optimal performance, in terms of the number of threads, is to benchmark. ImageMagick includes progressive threading when benchmarking a command and returns the elapsed time and efficiency for one or more threads. This can help you identify how many threads are the most efficient in your environment. Here is an example benchmark for threads 1-8:</p> 104 105<pre class="highlight"><code>-> magick -bench 40 model.png -sharpen 0x1 null: 106Performance[1]: 40i 0.712ips 1.000e 14.000u 0:14.040 107Performance[2]: 40i 1.362ips 0.657e 14.550u 0:07.340 108Performance[3]: 40i 2.033ips 0.741e 14.530u 0:04.920 109Performance[4]: 40i 2.667ips 0.789e 14.590u 0:03.750 110Performance[5]: 40i 3.236ips 0.820e 14.970u 0:03.090 111Performance[6]: 40i 3.802ips 0.842e 15.280u 0:02.630 112Performance[7]: 40i 4.274ips 0.857e 15.540u 0:02.340 113Performance[8]: 40i 4.831ips 0.872e 15.680u 0:02.070</code></pre> 114<p>Better performance correlates with higher values of IPS (iterations-per-second). In our example, 8 cores are optimal. However, in certain cases it might be optimal to set the number of threads to 1 (e.g. <code>-limit thread 1</code>) or to disable OpenMP completely. To disable this feature, add <code>--disable-openmp</code> to your configure script command line then rebuild and re-install ImageMagick.</p> 115</div> 116 </div> 117 </main><!-- /.container --> 118 <footer class="magick-footer"> 119 <div class="container-fluid"> 120 <a href="../www/security-policy.html">Security</a> • 121 <a href="../www/news.html">News</a> 122 123 <a href="openmp.html#"><img class="d-inline" id="wand" alt="And Now a Touch of Magick" width="16" height="16" src="../images/wand.ico"/></a> 124 125 <a href="../www/links.html">Related</a> • 126 <a href="../www/sitemap.html">Sitemap</a> 127 <br/> 128 <a href="../www/support.html">Sponsor</a> • 129 <a href="../www/cite.html">Cite</a> • 130 <a href="http://pgp.mit.edu/pks/lookup?op=get&search=0x89AB63D48277377A">Public Key</a> • 131 <a href="../www/https://imagemagick.org/script/contact.php">Contact Us</a> 132 <br/> 133 <a href="https://github.com/imagemagick/imagemagick" target="_blank" rel="noopener" aria-label="GitHub"><svg xmlns="http://www.w3.org/2000/svg" class="navbar-nav-svg" viewBox="0 0 512 499.36" width="2%" height="2%" role="img" focusable="false"><title>GitHub</title><path fill="currentColor" fill-rule="evenodd" d="M256 0C114.64 0 0 114.61 0 256c0 113.09 73.34 209 175.08 242.9 12.8 2.35 17.47-5.56 17.47-12.34 0-6.08-.22-22.18-.35-43.54-71.2 15.49-86.2-34.34-86.2-34.34-11.64-29.57-28.42-37.45-28.42-37.45-23.27-15.84 1.73-15.55 1.73-15.55 25.69 1.81 39.21 26.38 39.21 26.38 22.84 39.12 59.92 27.82 74.5 21.27 2.33-16.54 8.94-27.82 16.25-34.22-56.84-6.43-116.6-28.43-116.6-126.49 0-27.95 10-50.8 26.35-68.69-2.63-6.48-11.42-32.5 2.51-67.75 0 0 21.49-6.88 70.4 26.24a242.65 242.65 0 0 1 128.18 0c48.87-33.13 70.33-26.24 70.33-26.24 14 35.25 5.18 61.27 2.55 67.75 16.41 17.9 26.31 40.75 26.31 68.69 0 98.35-59.85 120-116.88 126.32 9.19 7.9 17.38 23.53 17.38 47.41 0 34.22-.31 61.83-.31 70.23 0 6.85 4.61 14.81 17.6 12.31C438.72 464.97 512 369.08 512 256.02 512 114.62 397.37 0 256 0z"/></svg></a> • 134 <a href="https://twitter.com/imagemagick" target="_blank" rel="noopener" aria-label="Twitter"><svg xmlns="http://www.w3.org/2000/svg" class="navbar-nav-svg" viewBox="0 0 512 416.32" width="2%" height="2%" role="img" focusable="false"><title>Twitter</title><path fill="currentColor" d="M160.83 416.32c193.2 0 298.92-160.22 298.92-298.92 0-4.51 0-9-.2-13.52A214 214 0 0 0 512 49.38a212.93 212.93 0 0 1-60.44 16.6 105.7 105.7 0 0 0 46.3-58.19 209 209 0 0 1-66.79 25.37 105.09 105.09 0 0 0-181.73 71.91 116.12 116.12 0 0 0 2.66 24c-87.28-4.3-164.73-46.3-216.56-109.82A105.48 105.48 0 0 0 68 159.6a106.27 106.27 0 0 1-47.53-13.11v1.43a105.28 105.28 0 0 0 84.21 103.06 105.67 105.67 0 0 1-47.33 1.84 105.06 105.06 0 0 0 98.14 72.94A210.72 210.72 0 0 1 25 370.84a202.17 202.17 0 0 1-25-1.43 298.85 298.85 0 0 0 160.83 46.92"/></svg></a> 135 <br/> 136 <small>© 1999-2021 ImageMagick Studio LLC</small> 137 </div> 138 </footer> 139 140 <!-- Javascript assets --> 141 <script src="assets/magick.js" ></script> 142 </body> 143</html> 144<!-- Magick Cache 13th February 2021 13:12 -->
