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Merge topic 'fix-openmp-reduction-with-few-threads'

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738c05ae8 fixes OMP reduction when using OMP_NUM_THREADS lt 4

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Robert Maynard <robert.maynard@kitware.com>
Merge-request: !2053
This commit is contained in:
Vicente Bolea 2020-04-23 15:51:50 +00:00 committed by Kitware Robot
commit d2ebecdb27
1 changed files with 6 additions and 3 deletions
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9
vtkm/cont/openmp/internal/FunctorsOpenMP.h
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@ -368,10 +368,13 @@ struct ReduceHelper
// Use the first (numThreads*2) values for initializing:
ReturnType accum = f(data[2 * tid], data[2 * tid + 1]);
vtkm::Id i = numThreads * 2;
const vtkm::Id unrollEnd = ((numVals / 4) * 4) - 4;
const vtkm::Id offset = numThreads * 2;
const vtkm::Id end = std::max(vtkm::Id(((numVals / 4) * 4) - 4), offset);
const vtkm::Id unrollEnd = end - ((end - offset) % 4);
vtkm::Id i = offset;
VTKM_OPENMP_DIRECTIVE(for schedule(static))
for (i = numThreads * 2; i < unrollEnd; i += 4)
for (i = offset; i < unrollEnd; i += 4)
{
const auto t1 = f(data[i], data[i + 1]);
const auto t2 = f(data[i + 2], data[i + 3]);