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
  .