Kokkos::RangePolicy

Kokkos::RangePolicy

Header File: Kokkos_Core.hpp

Usage:

Kokkos::RangePolicy<>(begin, end, args...)
Kokkos::RangePolicy<ARGS>(begin, end, args...)
Kokkos::RangePolicy<>(Space(), begin, end, args...)
Kokkos::RangePolicy<ARGS>(Space(), begin, end, args...)

RangePolicy defines an execution policy for a 1D iteration space starting at begin and going to end with an open interval.

Synopsis

template<class ... Args>
class Kokkos::RangePolicy {
  typedef RangePolicy execution_policy;
  typedef typename traits::index_type member_type ;
  typedef typename traits::index_type index_type;

  //Inherited from PolicyTraits<Args...> 
  using execution_space   = PolicyTraits<Args...>::execution_space;
  using schedule_type     = PolicyTraits<Args...>::schedule_type;
  using work_tag          = PolicyTraits<Args...>::work_tag;
  using index_type        = PolicyTraits<Args...>::index_type;
  using iteration_pattern = PolicyTraits<Args...>::iteration_pattern;
  using launch_bounds     = PolicyTraits<Args...>::launch_bounds;

  //Constructors
  RangePolicy(const RangePolicy&) = default;
  RangePolicy(RangePolicy&&) = default;

  inline RangePolicy();

  template<class ... Args>
  inline RangePolicy( const execution_space & work_space
           , const member_type work_begin
           , const member_type work_end
           , Args ... args);

  template<class ... Args>
  inline RangePolicy( const member_type work_begin
           , const member_type work_end
           , Args ... args);


  // retrieve chunk_size
  inline member_type chunk_size() const;
  // set chunk_size to a discrete value
  inline RangePolicy set_chunk_size(int chunk_size_);

  // return ExecSpace instance provided to the constructor
  KOKKOS_INLINE_FUNCTION const execution_space & space() const;
  // return Range begin 
  KOKKOS_INLINE_FUNCTION member_type begin() const;
  // return Range end 
  KOKKOS_INLINE_FUNCTION member_type end()   const;
};

Parameters:

Common Arguments for all Execution Policies

• Execution Policies generally accept compile time arguments via template parameters and runtime parameters via constructor arguments or setter functions.
• Template arguments can be given in arbitrary order.

Argument	Options	Purpose
ExecutionSpace	Serial, OpenMP, Threads, Cuda, HIP, SYCL, HPX	Specify the Execution Space to execute the kernel in. Defaults to Kokkos::DefaultExecutionSpace.
Schedule	Schedule<Dynamic>, Schedule<Static>	Specify scheduling policy for work items. Dynamic scheduling is implemented through a work stealing queue. Default is machine and backend specific.
IndexType	IndexType<int>	Specify integer type to be used for traversing the iteration space. Defaults to int64_t.
LaunchBounds	LaunchBounds<MaxThreads, MinBlocks>	Specifies hints to to the compiler about CUDA/HIP launch bounds.
WorkTag	SomeClass	Specify the work tag type used to call the functor operator. Any arbitrary type defaults to void.

Requirements:

Public Class Members

Constructors

• RangePolicy(): Default Constructor uninitialized policy.

• template<class ... InitArgs> 
  RangePolicy(const int64_t& begin, const int64_t& end, const InitArgs ... init_args)

  Provide a start and end index as well as optional arguments to control certain behavior (see below).

• template<class ... InitArgs> 
  RangePolicy(const ExecutionSpace& space, const int64_t& begin, const int64_t& end, const InitArgs ... init_args)

  Provide a start and end index and an ExecutionSpace instance to use as the execution resource, as well as optional arguments to control certain behavior (see below).

Optional InitArgs:

• ChunkSize : Provide a hint for optimal chunk-size to be used during scheduling.

Examples

  RangePolicy<> policy_1(N);
  RangePolicy<Cuda> policy_2(5,N-5);
  RangePolicy<Schedule<Dynamic>, OpenMP> policy_3(n,m);
  RangePolicy<IndexType<int>, Schedule<Dynamic>> policy_4(K);
  RangePolicy<> policy_6(-3,N+3, ChunkSize(8));
  RangePolicy<OpenMP> policy_7(OpenMP(), 0, N, ChunkSize(4));

Note: providing a single integer as a policy to a parallel pattern, implies a defaulted RangePolicy

  // These two calls are identical
  parallel_for("Loop", N, functor);
  parallel_for("Loop", RangePolicy<>(N), functor);