https://community.intel.com/t5/Intel-Integrated-Performance/Cannot-reduce-OpenMP-threads/m-p/975267#M20886 Hello, Could you attached a simple file that can show how the function is usded and some profiling result? For high CPU usage, can you add the following APIs, to reduced OpenMP BLOCK time? kmp_set_blocktime(0). Thanks, Chao Wed, 26 Dec 2012 08:19:21 GMT Chao_Y_Intel 2012-12-26T08:19:21Z https://community.intel.com/t5/Intel-Integrated-Performance/Cannot-reduce-OpenMP-threads/m-p/975266#M20885 <P>I can't get good performance with ippsFir_32f() past the point where it starts using FFTs internally (CORRECTION: that is, past the point where FFTs start getting processed in parallel at order 13). I get about 80% wait time and it's all caused by _kmp_launch_worker threads.&nbsp;</P> <P>I've tried</P> <P>- ippsSetNumThreads(1)<BR />- kmp_set_blocksize(200) via dll import&nbsp;</P> <P>Yet I still see multiple kmp threads in Vtune and overall cpu usage is about 75% between 4 cores. What could I be doing wrong here?</P> <P></P> Tue, 18 Dec 2012 03:41:16 GMT https://community.intel.com/t5/Intel-Integrated-Performance/Cannot-reduce-OpenMP-threads/m-p/975266#M20885 daven-hughes 2012-12-18T03:41:16Z https://community.intel.com/t5/Intel-Integrated-Performance/Cannot-reduce-OpenMP-threads/m-p/975267#M20886 Hello, Could you attached a simple file that can show how the function is usded and some profiling result? For high CPU usage, can you add the following APIs, to reduced OpenMP BLOCK time? kmp_set_blocktime(0). Thanks, Chao Wed, 26 Dec 2012 08:19:21 GMT https://community.intel.com/t5/Intel-Integrated-Performance/Cannot-reduce-OpenMP-threads/m-p/975267#M20886 Chao_Y_Intel 2012-12-26T08:19:21Z