List backend-specific IndexType for ExecutionPolicy (#552)

* added a link to the index types in the common args of execution policies * added info to executionSpaceConcept * added nested typedef to executionSpaceConcept * typo * remove spelled out list of types for different backends * added a note on possible performance impact of indextype
kokkos · Jul 30, 2024 · 65223d5 · 65223d5
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diff --git a/docs/source/API/core/Execution-Policies.rst b/docs/source/API/core/Execution-Policies.rst
@@ -81,8 +81,8 @@ Execution Policies generally accept compile time arguments via template paramete
       * 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``.
+      * e.g. ``IndexType<int>``
+      * Specify integer type to be used for traversing the iteration space. Defaults to the ``size_type`` of `ExecutionSpaceConcept <execution_spaces.html#typedefs>`__. Can affect the performance depending on the backend.
 
     * * LaunchBounds
       * ``LaunchBounds<MaxThreads, MinBlocks>``

diff --git a/docs/source/API/core/execution_spaces.rst b/docs/source/API/core/execution_spaces.rst
@@ -271,6 +271,7 @@ Synopsis
         typedef Device<execution_space, memory_space> device_type;
         typedef ... scratch_memory_space;
         typedef ... array_layout;
+        typedef ... size_type;
 
         ExecutionSpaceConcept();
         ExecutionSpaceConcept(const ExecutionSpaceConcept& src);
@@ -310,6 +311,8 @@ Typedefs
 
 * ``scratch_memory_space``: The ``ScratchMemorySpace`` that parallel patterns will use for allocation of scratch memory (for instance, as requested by a |KokkosTeamPolicy|_)
 
+* ``size_type``: The default integer type associated with this space. Signed or unsigned, 32 or 64 bit integer type, used as preferred type for indexing.
+
 Constructors
 ~~~~~~~~~~~~