[libcxx-commits] [PATCH] D70530: [pstl] OpenMP parallel back-end, WIP (Work in progress), just for discussion

[Mikhail Dvorskiy via Phabricator via libcxx-commits]

MikeDvorskiy updated this revision to Diff 245861.
MikeDvorskiy added a comment.

__parallel_transform_reduce pattern has been added.

In general case when a user passes user defined reductor, we canot rely on UDR from OpenMP spec, due to that requires "Identity" element. But STL  reduction algorithms have not "Identity" element, just "Initial" element.

So, we have to do "manual" parallel reduction - creating N accumulators, accumulating N results and  combining them int a final value.

P.S.
Of course,  for +, *, min, max operations we can add a specialization code which will use "reduction" clause.


Repository:
  rPSTL pstl

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D70530/new/

https://reviews.llvm.org/D70530

Files:
  include/pstl/internal/parallel_backend.h
  include/pstl/internal/parallel_backend_omp.h

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