{"id":446541,"date":"2025-11-17T17:55:00","date_gmt":"2025-11-17T17:55:00","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/udf-running-error-fluent-reports-not-compiled-for-parallel-use\/"},"modified":"2025-11-17T17:55:00","modified_gmt":"2025-11-17T17:55:00","slug":"udf-running-error-fluent-reports-not-compiled-for-parallel-use","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/udf-running-error-fluent-reports-not-compiled-for-parallel-use\/","title":{"rendered":"UDF running error. Fluent reports \u201cnot compiled for parallel use\u201d"},"content":{"rendered":"

<p data-start=”357″ data-end=”669″>I am having trouble loading a UDF that writes data after defined timestep. The UDF compiles without any errors, but Fluent refuses to load it whenever the code attempts to save data. The strange part is that this happens <strong data-start=”561″ data-end=”599″>even when using a single processor <\/strong>in the Fluent Launcher. I am using ANSYS 2025 R2 Student version.<\/p><p data-start=”671″ data-end=”738″>If I remove the file-writing part, the UDF loads and runs normally.<\/p><p data-start=”740″ data-end=”756″>Here is the UDF:<\/p><div class=”contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary”><div class=”sticky top-9″><div class=”absolute end-0 bottom-0 flex h-9 items-center pe-2″><div class=”bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs”> <\/div><\/div><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”><span class=”hljs-meta”>#<span class=”hljs-keyword”>include<\/span><\/span> <span class=”hljs-string”>”udf.h”<\/span>
\n<\/code><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”><span class=”hljs-meta”>#<span class=”hljs-keyword”>include<\/span><\/span> <span class=”hljs-string”><stdio.h><\/span>
\n<\/code><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”><span class=”hljs-meta”>#<span class=”hljs-keyword”>define<\/span><\/span> WRITE_FREQUENCY 10
\n<\/code><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”>DEFINE_EXECUTE_AT_END(write_flow_data)
\n<\/code><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”> <span class=”hljs-type”>int<\/span> current_ts = N_TIME;<\/p>\n

<span class=”hljs-keyword”>if<\/span> (current_ts % WRITE_FREQUENCY == <span class=”hljs-number”>0<\/span> && current_ts > <span class=”hljs-number”>0<\/span>)
\n<\/code><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”>  <span class=”hljs-meta”>#<span class=”hljs-keyword”>if<\/span><\/span> RP_HOST
\n <span class=”hljs-type”>char<\/span> filename[<span class=”hljs-number”>256<\/span>];
\n<\/code><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”> <span class=”hljs-built_in”>sprintf<\/span>(filename, <span class=”hljs-string”>”flowfield_ts_%d.dat”<\/span>, current_ts);
\n<\/code><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”> Message(<span class=”hljs-string”>”[UDF] Writing data file: %s\\n”<\/span>, filename);
\n<\/code><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”> Write_Data(filename);
\n<\/code><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”> Message(<span class=”hljs-string”>”[UDF] Done writing file.\\n”<\/span>);
\n<span class=”hljs-meta”>#<span class=”hljs-keyword”>endif<\/span><\/span> <\/code><\/div><\/div><p data-start=”1228″ data-end=”1265″>I also tried the alternative version:<\/p><div class=”contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary”><div class=”sticky top-9″><div class=”absolute end-0 bottom-0 flex h-9 items-center pe-2″><div class=”bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs”> <\/div><\/div><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre! language-c”><span class=”hljs-meta”>#<span class=”hljs-keyword”>if<\/span><\/span> RP_HOST
\n RP_Write_Data(filename);
\n<span class=”hljs-meta”>#<span class=”hljs-keyword”>endif<\/span><\/span>
\n<\/code><\/div><\/div><p data-start=”1325″ data-end=”1408″>Both versions compile correctly, but when I try to load the library Fluent reports:<\/p><div class=”contain-inline-size rounded-2xl relative bg-token-sidebar-surface-primary”><div class=”sticky top-9″><div class=”absolute end-0 bottom-0 flex h-9 items-center pe-2″><div class=”bg-token-bg-elevated-secondary text-token-text-secondary flex items-center gap-4 rounded-sm px-2 font-sans text-xs”> <\/div><\/div><\/div><div class=”overflow-y-auto p-4″ dir=”ltr”><code class=”whitespace-pre!”><span class=”hljs-symbol”>ERROR:<\/span> The UDF library you are trying <span class=”hljs-keyword”>to<\/span> load
\n(libudf\\win64\\<span class=”hljs-number”>2<\/span>ddp_node\\libudf.dll) <span class=”hljs-built_in”>is<\/span> <span class=”hljs-built_in”>not<\/span> compiled <span class=”hljs-keyword”>for<\/span> parallel use
\n<\/code><\/div><\/div><p data-start=”1535″ data-end=”1561″>This is confusing because:<\/p><ul data-start=”1563″ data-end=”1775″><li data-start=”1563″ data-end=”1599″><p data-start=”1565″ data-end=”1599″>I launch Fluent in <strong data-start=”1584″ data-end=”1599″>Serial mode<\/strong><\/p><\/li>\n

<li data-start=”1642″ data-end=”1706″><p data-start=”1644″ data-end=”1706″>The UDF only fails <strong data-start=”1663″ data-end=”1706″>when data-writing functions are present<\/strong><\/p><\/li>\n

<li data-start=”1707″ data-end=”1775″><p data-start=”1709″ data-end=”1775″>Without the Write_Data\/RP_Write_Data call, the same UDF loads fine<\/p><\/li>\n<\/ul>\n","protected":false},"template":"","class_list":["post-446541","topic","type-topic","status-publish","hentry","topic-tag-udf"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27825"],"_bbp_topic_id":["446541"],"_bbp_subscription":["621185","199"],"_bbp_author_ip":["89.134.24.16"],"_bbp_last_reply_id":["446627"],"_bbp_last_active_id":["446627"],"_bbp_last_active_time":["2025-11-18 13:53:49"],"_bbp_reply_count":["7"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["621185","199"],"_btv_view_count":["185"],"_bbp_topic_status":["unanswered"]},"test":"muhammaddanishmasoodedu-bme-hu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/446541","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\/446541\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=446541"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}