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llvm / llvm-project / pstl / c617ea87c3d30395b824661ebe5916013231429b
commitc617ea87c3d30395b824661ebe5916013231429b[log] [tgz]
authorLouis Dionne <ldionne@apple.com>Thu Mar 28 17:22:19 2019 +0000
committerCopybara-Service <copybara-worker@google.com>Tue Sep 01 14:40:59 2020 -0700
tree16c42e9b64e74c7226b018799673bd33adb4c205
parent070534ff405df98ec62178633bdf3ae094aeb57d [diff]
[pstl] Introduce forward declarations

Necessary when pstl is included from with <algorithm> and <numeric> to
prevent a partially declared standard library when pstl itself uses
algorithms from <algorithm> and <numeric>.

Also, this patch makes sure that configuration comes via standard headers.
Directly including pstl_config.h in implementation files is incompatible
with inclusion of pstl into a standard library implementation which
provides it's own library wide configuration and may configure the
library differently to the pstl_config.h used by the standalone
implementation.

Differential Revision: https://reviews.llvm.org/D59122

llvm-svn: 357189
GitOrigin-RevId: 1dd1b5d5f254ef25dd184d71cb60db92a750d96b
10 files changed
tree: 16c42e9b64e74c7226b018799673bd33adb4c205
  1. cmake/
  2. include/
  3. test/
  4. .arcconfig
  5. .clang-format
  6. CMakeLists.txt
  7. CREDITS.txt
  8. LICENSE.txt
  9. ParallelSTLConfig.cmake.in
  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.