commit c0c4f93940f86e8d108e84a60104bfda4aad66b3
author Dmitriy Korchemkin <dmitriy.korchemkin@gmail.com> Thu Aug 18 22:10:17 2022 +0300
committer Dmitriy Korchemkin <dmitriy.korchemkin@gmail.com> Tue Sep 20 11:06:22 2022 +0300
tree 2cbbba12cd9d231f1a10926e055d122ba457f416
parent fc826c578032c19054a27e5bcac626a3ac6883ac

Change implementation of parallel for

Implemented templated invocation routines for ParallelFor backends
in order to improve loop body inlining.

Several modifications of ParallelFor implementation using CXX threads:
 - Index order changed from interleaved to sequential
 - Static task scheduling replaced with dynamic (controlled by
   kWorkBlocksPerThread)
 - Changed index retrieval to atomic

Modifications of OpenMP backend:
 - Changed loop scheduling to guided

Changing index order from interleaved to sequential in parallel seem
to significantly improve run-times of parallel loops, for example in
evaluation of jacobian and residuals.

Other modifications provide minor improvements for unbalanced
sub-problem lengths and parallel for loops with small number of
computation per operation.

Single-threaded performance was improved by avoiding costs of
wrapping parallel loop bodies in std::function.

On BAL dataset the following improvements in time consumed for
evaluation of residuals or jacobian and residuals were observed:

                                     OLD           NEW        OLD/NEW
                 dataset threads     r     J     r     J     r     J
problem-257-65132-pre.txt      1 0.025  0.079  0.025  0.074 1.016 1.056
problem-257-65132-pre.txt      2 0.030  0.062  0.022  0.050 1.333 1.246
problem-257-65132-pre.txt      4 0.023  0.052  0.014  0.034 1.592 1.515
problem-257-65132-pre.txt      8 0.015  0.035  0.010  0.025 1.477 1.401
problem-257-65132-pre.txt     16 0.011  0.027  0.008  0.019 1.365 1.377
problem-356-226730-pre.txt     1 0.150  0.442  0.147  0.412 1.017 1.070
problem-356-226730-pre.txt     2 0.155  0.322  0.100  0.281 1.542 1.145
problem-356-226730-pre.txt     4 0.129  0.291  0.089  0.196 1.439 1.485
problem-356-226730-pre.txt     8 0.091  0.184  0.066  0.139 1.381 1.319
problem-356-226730-pre.txt    16 0.070  0.148  0.055  0.110 1.272 1.340
problem-1723-156502-pre.txt    1 0.084  0.243  0.082  0.229 1.023 1.063
problem-1723-156502-pre.txt    2 0.088  0.188  0.055  0.154 1.589 1.222
problem-1723-156502-pre.txt    4 0.072  0.159  0.049  0.108 1.475 1.475
problem-1723-156502-pre.txt    8 0.050  0.105  0.037  0.077 1.348 1.368
problem-1723-156502-pre.txt   16 0.038  0.083  0.030  0.062 1.269 1.344
problem-1778-993923-pre.txt    1 0.621  1.777  0.609  1.667 1.018 1.065
problem-1778-993923-pre.txt    2 0.621  1.273  0.415  1.199 1.494 1.061
problem-1778-993923-pre.txt    4 0.514  1.140  0.361  0.786 1.421 1.449
problem-1778-993923-pre.txt    8 0.365  0.808  0.277  0.559 1.319 1.443
problem-1778-993923-pre.txt   16 0.279  0.608  0.223  0.441 1.252 1.379
problem-13682-4456117-pre.txt  1 3.877 10.726  3.738 10.082 1.037 1.063
problem-13682-4456117-pre.txt  2 3.310  7.170  2.423  6.448 1.366 1.111
problem-13682-4456117-pre.txt  4 3.070  6.344  2.064  4.474 1.486 1.417
problem-13682-4456117-pre.txt  8 2.051  4.612  1.527  3.133 1.343 1.472
problem-13682-4456117-pre.txt 16 1.549  3.453  1.218  2.488 1.271 1.387

Run time in seconds for a single evaluation, using evaluation_benchmark
numactl -N 0 -m 0 ./bin/evaluation_benchmark --bal_root ${path_to_BAL}
Evaluation was performed on 28-core CPU.

Note: performance when running across numa-nodes degrades in both old
and proposed implementations, thus the test was executed limiting memory
and compute resources allocation to a single numa-node.

Change-Id: Ia195580bdab9d05c95ac983bfe37b045eecfaf49