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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// SPDX-FileCopyrightText: Copyright Contributors to the Kokkos project
#include <Kokkos_Core.hpp>
#include <cstdio>
//
// First reduction (parallel_reduce) example:
// 1. Start up Kokkos
// 2. Execute a parallel_reduce loop in the default execution space,
// using a C++11 lambda to define the loop body
// 3. Shut down Kokkos
//
// Compare this example to 02_simple_reduce, which uses a functor to
// define the loop body of the parallel_reduce.
//
int main(int argc, char* argv[]) {
Kokkos::initialize(argc, argv);
const int n = 10;
// Compute the sum of squares of integers from 0 to n-1, in
// parallel, using Kokkos. This time, use a lambda instead of a
// functor. The lambda takes the same arguments as the functor's
// operator().
int sum = 0;
// The KOKKOS_LAMBDA macro replaces the capture-by-value clause [=].
// It also handles any other syntax needed for CUDA.
Kokkos::parallel_reduce(
n, KOKKOS_LAMBDA(const int i, int& lsum) { lsum += i * i; }, sum);
printf(
"Sum of squares of integers from 0 to %i, "
"computed in parallel, is %i\n",
n - 1, sum);
// Compare to a sequential loop.
int seqSum = 0;
for (int i = 0; i < n; ++i) {
seqSum += i * i;
}
printf(
"Sum of squares of integers from 0 to %i, "
"computed sequentially, is %i\n",
n - 1, seqSum);
Kokkos::finalize();
return (sum == seqSum) ? 0 : -1;
}
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