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Date: Mon, 22 Jun 2015 20:44:29 +0300
From: Solar Designer <>
Subject: tuning OMP_SCALE on MIC (was: Lei's weekly report #7)

On Mon, Jun 22, 2015 at 10:12:16PM +0800, Lei Zhang wrote:
> I ran through all self-tests on MIC with OMP_NUM_THREADS=240 and OMP_NUM_THREADS=60 respectively, and compared the results to find out which formats perform better with fewer threads. 
> There're 309 formats in total (excluding dominosec8, which segfaults on MIC for the moment), and 125 of them run faster with OMP_NUM_THREADS=60. I may need to further tune OMP_SCALEs in those formats. I'll investigate that later.
> The list of those formats is attached.

Thanks!  For most of them, we're simply aware that our current approach
at parallelizing them is extremely inefficient.  They are too fast for
it.  So tuning of OMP_SCALE is primarily needed for a subset of them -
the slow ones, where good efficiency can be achieved despite of the
current approach at parallelization.  Thus, please sort them by c/s rate
obtained when running 1 thread (either a non-OpenMP build or with
OMP_NUM_THREADS=1), in absolute terms, and start tuning OMP_SCALE
(obviously in an OpenMP-enabled build and running 240 threads this time)
with the slowest format.  Then proceed to the faster ones.


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