{"id":4943,"date":"2022-08-25T06:44:36","date_gmt":"2022-08-25T01:14:36","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-openmp-when-can-a-loop-be-parallelized\/"},"modified":"2022-08-25T06:44:36","modified_gmt":"2022-08-25T01:14:36","slug":"solved-openmp-when-can-a-loop-be-parallelized","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-openmp-when-can-a-loop-be-parallelized\/","title":{"rendered":"[Solved] OPenMP: When can a Loop be parallelized"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-35997431\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"35997431\" data-parentid=\"35996639\" data-score=\"2\" data-position-on-page=\"1\" data-highest-scored=\"1\" data-question-has-accepted-highest-score=\"1\" itemprop=\"acceptedAnswer\" itemscope itemtype=\"https:\/\/schema.org\/Answer\">\n<div class=\"post-layout\">\n<div class=\"votecell post-layout--left\"><\/div>\n<div class=\"answercell post-layout--right\">\n<div class=\"s-prose js-post-body\" itemprop=\"text\">\n<p>I will not do your HW, but I will give a hint. When playing around with OpenMp for loops, you should be alert about the scope of the variables. For example:<\/p>\n<pre><code>#pragma omp parallel for\nfor(int x=0; x &lt; width; x++)\n{\n    for(int y=0; y &lt; height; y++)\n    {\n        finalImage[x][y] = RenderPixel(x,y, &amp;sceneData);\n    }\n}\n<\/code><\/pre>\n<p>is OK, since <code>x<\/code> and <code>y<\/code> are private variables.<\/p>\n<p>What about<\/p>\n<pre><code>int x,y;\n#pragma omp parallel for\nfor(x=0; x &lt; width; x++)\n{\n    for(y=0; y &lt; height; y++)\n    {\n        finalImage[x][y] = RenderPixel(x,y, &amp;sceneData);\n    }\n}\n<\/code><\/pre>\n<p>?<\/p>\n<p>Here, we have defined <code>x<\/code> and <code>y<\/code> outside of the for loop. Now consider <code>y<\/code>. Every thread will access\/write it without any synchronization, thus data races will occur, which are very likely to result in logical errors.<\/p>\n<p>Read more <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/supercomputingblog.com\/openmp\/tutorial-parallel-for-loops-with-openmp\/\">here<\/a> and good luck with your HW.<\/p>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\"><\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved OPenMP: When can a Loop be parallelized <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] I will not do your HW, but I will give a hint. When playing around with OpenMp for loops, you should be alert about the scope of the variables. For example: #pragma omp parallel for for(int x=0; x &lt; width; x++) { for(int y=0; y &lt; height; y++) { finalImage[x][y] = RenderPixel(x,y, &amp;sceneData); } &#8230; <a title=\"[Solved] OPenMP: When can a Loop be parallelized\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-openmp-when-can-a-loop-be-parallelized\/\" aria-label=\"More on [Solved] OPenMP: When can a Loop be parallelized\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[324,1164,1163],"class_list":["post-4943","post","type-post","status-publish","format-standard","hentry","category-solved","tag-c","tag-openmp","tag-parallel-processing"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] OPenMP: When can a Loop be parallelized - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-openmp-when-can-a-loop-be-parallelized\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] OPenMP: When can a Loop be parallelized - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] I will not do your HW, but I will give a hint. When playing around with OpenMp for loops, you should be alert about the scope of the variables. For example: #pragma omp parallel for for(int x=0; x &lt; width; x++) { for(int y=0; y &lt; height; y++) { finalImage[x][y] = RenderPixel(x,y, &amp;sceneData); } ... 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When playing around with OpenMp for loops, you should be alert about the scope of the variables. For example: #pragma omp parallel for for(int x=0; x &lt; width; x++) { for(int y=0; y &lt; height; y++) { finalImage[x][y] = RenderPixel(x,y, &amp;sceneData); } ... 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