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llvm / llvm-project / pstl / b06d83885ff1c50766ef85940bb2a26d19c91c92
commitb06d83885ff1c50766ef85940bb2a26d19c91c92[log] [tgz]
authorLouis Dionne <ldionne@apple.com>Tue Jun 18 19:34:04 2019 +0000
committerCopybara-Service <copybara-worker@google.com>Tue Sep 01 14:42:34 2020 -0700
treeb255942fe992da19522db67eebe7ece6c84aa1b3
parenta3c81119d3d9de259bb79736ef15a7a9ae0715db [diff]
[pstl] Remove stray usage of pstl::execution instead of std::execution

llvm-svn: 363723
GitOrigin-RevId: 9d54063c823964cd565023fd7f2ed21431e99f90
4 files changed
tree: b255942fe992da19522db67eebe7ece6c84aa1b3
  1. cmake/
  2. docs/
  3. include/
  4. test/
  5. .arcconfig
  6. .clang-format
  7. CMakeLists.txt
  8. CREDITS.txt
  9. LICENSE.txt
  10. README.md
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.