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Chandler Carruth 57b08b0944 Update more file headers across all of the LLVM projects in the monorepo 
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351648
 		2019-01-19 10:56:40 +00:00
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build Update more file headers across all of the LLVM projects in the monorepo 2019-01-19 10:56:40 +00:00
cmake Update more file headers across all of the LLVM projects in the monorepo 2019-01-19 10:56:40 +00:00
include/pstl Update more file headers across all of the LLVM projects in the monorepo 2019-01-19 10:56:40 +00:00
test Update more file headers across all of the LLVM projects in the monorepo 2019-01-19 10:56:40 +00:00
.arcconfig
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.clang-format
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CMakeLists.txt Update more file headers across all of the LLVM projects in the monorepo 2019-01-19 10:56:40 +00:00
CREDITS.txt
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LICENSE.txt Install new LLVM license structure and new developer policy. 2019-01-19 06:14:24 +00:00
ParallelSTLConfig.cmake.in Update more file headers across all of the LLVM projects in the monorepo 2019-01-19 10:56:40 +00:00
README.md [NFC] Fix formatting of README.md for better rendering 2019-01-07 16:54:02 +00:00

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.