https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Comparison-Pentium-4-and-Woodcrest/m-p/905192#M11576 <P>For our research we want to compare the Intel MKL sparse matrix vector multiplication "<EM>mkl_dcsrmv</EM>"on a Pentium 4 2.4 Ghz and one core of the Woodcrest processor. </P> <P>I read in the documentation that MKL uses OpenMP for threading, however even I set OMP_NUM_THREADS to 1 and MKL_SERIAL=yes I still see in V-Tune that this function will spread to multiple logical processors on the Woodcrest processor. </P> <P>The function"<EM>mkl_dcsrmv</EM>" translates for the Pentium 4to "<EM>mkl_spblas_p4_dcsrmmsysm</EM>" and for the Woodcrestto "<EM>L__mlk_spblas_p4m_dcsrmmsym_304__par_loop0</EM>" </P> <P>Even though this last function is called in a single thread, why does it spread out to multiple processors ? Can I deactivate this ? </P> <P></P> Wed, 18 Oct 2006 21:59:55 GMT Anonymous62 2006-10-18T21:59:55Z https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Comparison-Pentium-4-and-Woodcrest/m-p/905192#M11576 <P>For our research we want to compare the Intel MKL sparse matrix vector multiplication "<EM>mkl_dcsrmv</EM>"on a Pentium 4 2.4 Ghz and one core of the Woodcrest processor. </P> <P>I read in the documentation that MKL uses OpenMP for threading, however even I set OMP_NUM_THREADS to 1 and MKL_SERIAL=yes I still see in V-Tune that this function will spread to multiple logical processors on the Woodcrest processor. </P> <P>The function"<EM>mkl_dcsrmv</EM>" translates for the Pentium 4to "<EM>mkl_spblas_p4_dcsrmmsysm</EM>" and for the Woodcrestto "<EM>L__mlk_spblas_p4m_dcsrmmsym_304__par_loop0</EM>" </P> <P>Even though this last function is called in a single thread, why does it spread out to multiple processors ? Can I deactivate this ? </P> <P></P> Wed, 18 Oct 2006 21:59:55 GMT https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Comparison-Pentium-4-and-Woodcrest/m-p/905192#M11576 Anonymous62 2006-10-18T21:59:55Z https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Comparison-Pentium-4-and-Woodcrest/m-p/905193#M11577 I am guessing that you are running a single thread, but it is moving around among the cores. You could boot up your OS with 1 processor, or you could use the scheme appropriate to your OS for requesting the job to stay on a specified core (Windows Task Manager affinity box checks, or linux taskset or numactl, depending on your OS version). There is a good chance it will perform better when restricted to a single core, if it has that core to itself. Also, there is a chance of getting more repeatable VTune results this way.<BR /> Thu, 19 Oct 2006 01:44:50 GMT https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/Comparison-Pentium-4-and-Woodcrest/m-p/905193#M11577 TimP 2006-10-19T01:44:50Z