OpenMathLib / OpenMathLib/OpenBLAS

Make ICOPY_OPERATION threaded?

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Description

In some multi-threaded versions of OpenBLAS, the ICOPY_OPERATION (packing for A) seems to take 6-13X more time than the actual KERNEL_OPERATION(s). Is it possible to make this operation multi-threaded?

    /* Copy local region of A into workspace */
    START_RPCC();
    ICOPY_OPERATION(min_l, min_i, a, lda, ls, m_from, sa);
    STOP_RPCC(copy_A);
  48.09%  pt_main_thread  libomp.so                                               [.] bool __kmp_wait_template<kmp_flag_64<false, true>, true, false, true>(kmp_info*, kmp_flag_64<false, true>*, void*)
  18.23%  pt_main_thread  libgomp.so.1.0.0                                        [.] do_wait
   9.01%  pt_main_thread  libopenblasp-r0.3.27.dev.so                             [.] sbgemm_incopy_POWER10
   2.85%  pt_main_thread  libopenblasp-r0.3.27.dev.so                             [.] sbgemm_kernel_POWER10
   1.33%  pt_main_thread  libopenblasp-r0.3.27.dev.so                             [.] inner_thread

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Research direction

Start by tracing the ICOPY_OPERATION call in the shown packing path and reviewing the supplied profiling data for sbgemm_incopy_POWER10, thread waits, and KERNEL_OPERATION. Determine whether the packing operation can be threaded without conflicting with the existing parallel work; done means a validated approach with benchmark evidence showing the packing bottleneck is addressed.

Written by the indexing model from the issue text.

Assessment

Tech stack
c
Domain
performance
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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