{"id":308054,"date":"2023-09-22T09:57:59","date_gmt":"2023-09-22T09:57:59","guid":{"rendered":"\/forum\/forums\/topic\/information-on-parallelization-performance\/"},"modified":"2023-09-22T09:57:59","modified_gmt":"2023-09-22T09:57:59","slug":"information-on-parallelization-performance","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/information-on-parallelization-performance\/","title":{"rendered":"Information on parallelization performance"},"content":{"rendered":"<div class=\"x_elementToProof\">Good morning,<\/div>\n<div class=\"x_elementToProof\">&nbsp;<\/div>\n<div class=\"x_elementToProof\">I am running ANSYS Fluent CFD simulations on an HPC cluster.<\/div>\n<div class=\"x_elementToProof\">I am trying to simulate particle dispersion around a urban area, with a domain size of 10x10km, and 8M cells.<\/div>\n<div class=\"x_elementToProof\">This week I was ready to launch my final simulation in the cluster, but I have found an unexpected issue.&nbsp;<\/div>\n<div class=\"x_elementToProof\">For all the testing that I have been doing, I have been running my simulation on 4 nodes with 20 tasks per node.<br aria-hidden=\"true\">Now, in order to obtain faster results for the real simulation, I wanted to increase the number of nodes to 8-12, but I just realised that when I increase this number, my simulation diverges and crashes after a few minutes.<\/div>\n<div class=\"x_elementToProof\">&nbsp;<\/div>\n<div class=\"x_elementToProof\">I first thought that it could be a problem with the mesh of my simulation, but then I do not understand why the simulation with 4(x20) runs without problems (currently running for 10h, see attached residuals evolution). On the other hand, I have tried launching exactly the same simulation (copy-paste) with 5, 6, 7, 8, 10, 12 and 16(x20) nodes, and they all crash after ~ 200 iterations (see also attached a typical profile). Does this make sense? Am I missing something?<\/div>\n<div class=\"x_elementToProof\">&nbsp;<\/div>\n<div class=\"x_elementToProof\">I tried finding some information online about such an issue but I didn&#8217;t manage to finde any explanation.<\/div>\n<div class=\"x_elementToProof\">Do you think it could be a parallelization issue? In that case, do you have any advice for me? Should I use more or less tasks per node when increasing my number of nodes?<\/div>\n<div class=\"x_elementToProof\">&nbsp;<\/div>\n<div class=\"x_elementToProof\">Thank you very much in advance.<\/div>\n<div class=\"x_elementToProof\">&nbsp;<\/div>\n<div class=\"x_elementToProof\">Details of my simulation: Transient, LES, double precision, PISO P-V coupling, Second Order Upwind mom, Second order pressure.<\/div>\n","protected":false},"template":"","class_list":["post-308054","topic","type-topic","status-closed","hentry","topic-tag-divergence-detected","topic-tag-dpm-model","topic-tag-dpm-tracking","topic-tag-DPMUDFParallel-1","topic-tag-performance-issues-2"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["279784","15180"],"_bbp_author_ip":["23.206.193.154"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["397"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["308054"],"_bbp_forum_id":["27792"],"_bbp_engagement":["15180","279784"],"_bbp_voice_count":["2"],"_bbp_reply_count":["2"],"_bbp_last_reply_id":["309098"],"_bbp_last_active_id":["309098"],"_bbp_last_active_time":["2023-09-27 13:50:47"]},"test":"joan-baptista-rico-orerocern-ch"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/308054","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/308054\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=308054"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}