libcxx/src/pstl/libdispatch.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include <__algorithm/min.h>
  10 #include <__config>
  11 #include <__pstl/backends/libdispatch.h>
  12 #include <dispatch/dispatch.h>
  13
  14 _LIBCPP_BEGIN_NAMESPACE_STD
  15 namespace __pstl::__libdispatch {
  16
  17 void __dispatch_apply(size_t chunk_count, void* context, void (*func)(void* context, size_t chunk)) noexcept {
  18   ::dispatch_apply_f(chunk_count, DISPATCH_APPLY_AUTO, context, func);
  19 }
  20
  21 __chunk_partitions __partition_chunks(ptrdiff_t element_count) noexcept {
  22   __chunk_partitions partitions;
  23   partitions.__chunk_count_      = std::max<ptrdiff_t>(1, element_count / 256);
  24   partitions.__chunk_size_       = element_count / partitions.__chunk_count_;
  25   partitions.__first_chunk_size_ = element_count - (partitions.__chunk_count_ - 1) * partitions.__chunk_size_;
  26   if (partitions.__chunk_count_ == 0 && element_count > 0)
  27     partitions.__chunk_count_ = 1;
  28   return partitions;
  29 }
  30
  31 } // namespace __pstl::__libdispatch
  32 _LIBCPP_END_NAMESPACE_STD