Cannot reduce OpenMP threads

Cannot reduce OpenMP threads

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. 

I've tried

- ippsSetNumThreads(1)
- kmp_set_blocksize(200) via dll import 

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?

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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?


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