Kokkos::subview

Kokkos::subview

Header File: Kokkos_Core.hpp

Usage:

auto s = subview(view,std::pair<int,int>(5,191),Kokkos::ALL,1);

Creates a Kokkos::View viewing a subset of another Kokkos::View.

Synopsis

template <class ViewType, class... Args>
IMPL_DETAIL subview(const ViewType& v, Args ... args);

Description

• template <class ViewType, class... Args>
  IMPL_DETAIL subview(const ViewType& v, Args ... args);

  Returns a new Kokkos::View s viewing a subset of v specified by args.... The return type of subview is an implementation detail and is determined by the types in Args....

  Subset selection:

  • For every integer argument in args... the rank of the returned view is one smaller than the rank of v and the values referenced by s correspond to the values associated with using the integer argument in the corresponding position during indexing into v.
  • Passing Kokkos::ALL as the rth argument is equivalent to passing pair<ptrdiff_t,ptrdiff_t>(0,v.extent(r)) as the rth argument.
  • If the rth argument arg_r is the dth range (std::pair, Kokkos::pair or Kokkos::ALL) in the argument list than s.extent(d) = arg_r.second-arg_r.first, and dimension d of s references the range [arg_r.first,arg_r.second) of dimension r of v.

  Restrictions:

  • sizeof...(args) is equal to ViewType::rank.
  • Valid arguments are of type:
    • std::pair<iType,iType> with std::is_integral<iType>::value being true.
    • Kokkos::pair<iType,iType> with std::is_integral<iType>::value being true.
    • iType with std::is_integral<iType>::value being true.
    • decltype(Kokkos::ALL)
  • If the rth argument arg_r is of type std::pair<iType,iType> or Kokkos::pair<iType,iType> it must meet:
    • arg_r.first >= 0
    • arg_r.second <= v.extent(r)
    • arg_r.first <= arg_r.second
  • If the rth argument arg_r is an integral it must meet:
    • arg_r >= 0
    • arg_r < v.extent(r)

Examples

  Kokkos::View<double***[5]> a("A",N0,N1,N2);

  auto s  = Kokkos::subview(a,
                std::pair<int,int>(3,15),
                5,
                Kokkos::ALL,
                Kokkos::ALL);
  for(int i0 = 0; i0 < s.extent(0); i0++) 
  for(int i1 = 0; i1 < s.extent(1); i1++) 
  for(int i2 = 0; i2 < s.extent(2); i2++) {
    assert(s(i0,i1,i2) == a(i0+3,5,i1,i2));
  }

  auto s3415 = Kokkos::subview(a,3,4,1,5);
  assert(s3415() == a(3,4,1,5));