Add example code referenced in issue #452

[ajpowelsnl]

This PR adds example code from Compiler Explorer to MinLoc built-in reducer.

[dalg24]

The indentation of the entire code block does not look right

[ajpowelsnl]

The indentation of the entire code block does not look right

Fixed indentation (w/ spaces), so it now looks like example in View.

[masterleinad]

clang-format-8 gives

#include <Kokkos_Core.hpp>
struct Idx3D_t {
  int value[3];
  int& operator[](int i) { return value[i]; }
  const int& operator[](int i) const { return value[i]; }
};
template <>
struct Kokkos::reduction_identity<Idx3D_t> {
  static constexpr Idx3D_t min() { return {0, 0, 0}; }
};
int main(int argc, char* argv[]) {
  Kokkos::initialize(argc, argv);
  {
    Kokkos::View<double***> a("A", 5, 5, 5);
    Kokkos::deep_copy(a, 10);
    a(2, 3, 1)        = 5;
    using MinLoc_t    = Kokkos::MinLoc<double, Idx3D_t>;
    using MinLocVal_t = typename MinLoc_t::value_type;
    MinLocVal_t result;
    Kokkos::parallel_reduce(
        Kokkos::MDRangePolicy<Kokkos::Rank<3>>({0, 0, 0}, {5, 5, 5}),
        KOKKOS_LAMBDA(int i, int j, int k, MinLocVal_t& val) {
          if (a(i, j, k) < val.val) {
            val.val    = a(i, j, k);
            val.loc[0] = i;
            val.loc[1] = j;
            val.loc[2] = k;
          }
        },
        MinLoc_t(result));
    printf("%lf %i %i %i\n", result.val, result.loc[0], result.loc[1],
           result.loc[2]);
  }
  Kokkos::finalize();
}

(without the preceding whitespace).

[ajpowelsnl]

So I tried your clang-formatted version (above), but it did not render correctly, and had many warnings (e.g., "WARNING: Block quote ends without a blank line; unexpected unindent"). It is possible that we do not have our project set up correctly / completely for C++ (see #451). Example formatting can be a topic for tomorrow.

[nmm0]

We need to tab over the output of clang format, directives need to be tabbed

[masterleinad]

Can you use four whitespaces instead of one tab?

[ajpowelsnl]

sure. I'll have to do it by hand, though.

[masterleinad]

Something like %s/\t/ /g in vi.

[masterleinad]

Fine with me.