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llvm / llvm-project / pstl / 24629d574e5c676fd01ec1aeb29ff61e30f2812a
commit24629d574e5c676fd01ec1aeb29ff61e30f2812a[log] [tgz]
authorLouis Dionne <ldionne@apple.com>Tue Aug 13 12:49:00 2019 +0000
committerCopybara-Service <copybara-worker@google.com>Tue Sep 01 14:44:34 2020 -0700
tree8ed894cf32e72148b94dc278f7d1bd2013422fcc
parent1e1f0ea0d6597290b298c9e3e737d73e9e154ef3 [diff]
[pstl] Allow customizing whether per-TU insulation is provided

Like we do in libc++, PSTL needs the ability to constrain
ABI-unstable symbols to each translation unit. This is OFF by
default (like for libc++), because most people don't care about
this and there is a cost associated to enabling the option (code
bloat because templates are not deduped across TUs).

I'm using '#pragma clang attribute push' to avoid marking each
declaration with an attribute, which quickly becomes difficult
to maintain.

llvm-svn: 368684
GitOrigin-RevId: 1b6d6e595b5e27566579c03923667aaab58bd3cd
22 files changed
tree: 8ed894cf32e72148b94dc278f7d1bd2013422fcc
  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.