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llvm / llvm-project / pstl / ec797beeca73d8156638b076fd22f6c6515dd17c
commitec797beeca73d8156638b076fd22f6c6515dd17c[log] [tgz]
authorDvorskiy, Mikhail <mikhail.dvorskiy@intel.com>Mon Sep 14 14:20:32 2020 +0300
committerCopybara-Service <copybara-worker@google.com>Thu Oct 29 19:42:39 2020 -0700
tree4e3bc640a7f7cf358e53e7f4b3696d12d71a58e5
parent408fd790b40067229fd3119cf3fedd3ba895cd8b [diff]
[pstl] Support Threading Building Blocks 2020 (oneTBB) for "tbb" parallel backend.

After the changes the "tbb" parallel backend will work with old TBB versions(TBB_INTERFACE_VERSION <= 12000) and new ones (TBB 2020 and greater)

More about oneTBB:
https://github.com/oneapi-src/oneTBB

Phabricator Review:
https://reviews.llvm.org/D87380

GitOrigin-RevId: 0b2e0e80d963f3498705a38e8d02eafe541ca9d6
1 file changed
tree: 4e3bc640a7f7cf358e53e7f4b3696d12d71a58e5
  1. .clang-format
  2. CMakeLists.txt
  3. CREDITS.txt
  4. LICENSE.txt
  5. README.md
  6. cmake/
  7. docs/
  8. include/
  9. test/
README.md

Parallel STL

Parallel STL is an implementation of the C++ standard library algorithms with support for execution policies, as specified in ISO/IEC 14882:2017 standard, commonly called C++17. The implementation also supports the unsequenced execution policy specified in Parallelism TS version 2 and proposed for the next version of the C++ standard in the C++ working group paper P1001. Parallel STL offers efficient support for both parallel and vectorized execution of algorithms. For sequential execution, it relies on an available implementation of the C++ standard library.

Prerequisites

To use Parallel STL, you must have the following software installed:

  • C++ compiler with:
    • Support for C++11
    • Support for OpenMP* 4.0 SIMD constructs
  • Threading Building Blocks (TBB) which is available for download at https://github.com/01org/tbb/

Known issues and limitations

  • unseq and par_unseq policies only have effect with compilers that support #pragma omp simd or #pragma simd.
  • Parallel and vector execution is only supported for the algorithms if random access iterators are provided, while for other iterator types the execution will remain serial.
  • The following algorithms do not allow efficient SIMD execution: includes, inplace_merge, merge, nth_element, partial_sort, partial_sort_copy, set_difference, set_intersection, set_symmetric_difference, set_union, sort, stable_partition, stable_sort, unique.
  • The initial value type for exclusive_scan, inclusive_scan, transform_exclusive_scan, transform_inclusive_scan shall be DefaultConstructible. A default constructed-instance of the initial value type shall be the identity element for the specified binary operation.
  • For max_element, min_element, minmax_element, partial_sort, partial_sort_copy, sort, stable_sort the dereferenced value type of the provided iterators shall be DefaultConstructible.
  • For remove, remove_if, unique the dereferenced value type of the provided iterators shall be MoveConstructible.
  • The following algorithms require additional O(n) memory space for parallel execution: copy_if, inplace_merge, partial_sort, partial_sort_copy, partition_copy, remove, remove_if, rotate, sort, stable_sort, unique, unique_copy.