launch_bounds_reduce.cpp
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launch_bounds_reduce.cpp
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			/*
			//@HEADER
			// ************************************************************************
			//
			// Kokkos v. 2.0
			// Copyright (2014) Sandia Corporation
			//
			// Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
			// the U.S. Government retains certain rights in this software.
			//
			// Redistribution and use in source and binary forms, with or without
			// modification, are permitted provided that the following conditions are
			// met:
			//
			// 1. Redistributions of source code must retain the above copyright
			// notice, this list of conditions and the following disclaimer.
			//
			// 2. Redistributions in binary form must reproduce the above copyright
			// notice, this list of conditions and the following disclaimer in the
			// documentation and/or other materials provided with the distribution.
			//
			// 3. Neither the name of the Corporation nor the names of the
			// contributors may be used to endorse or promote products derived from
			// this software without specific prior written permission.
			//
			// THIS SOFTWARE IS PROVIDED BY SANDIA CORPORATION "AS IS" AND ANY
			// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
			// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
			// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SANDIA CORPORATION OR THE
			// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
			// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
			// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
			// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
			// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
			// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
			// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
			//
			// Questions? Contact H. Carter Edwards (hcedwar@sandia.gov)
			//
			// ************************************************************************
			//@HEADER
			*/

			#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 functor to define the loop body
			// 3. Shut down Kokkos
			//
			struct collision {
			// Reduction functor
			// For each i, we generate 10 hashes, look for and count collisions
			// We use parallel_reduce to count the total collisions
			// Note that we're just counting collisions within the 10 generated
			// one i.
			// This function was chosen as one that very simply can increase the
			// register count.
			typedef int value_type;

			KOKKOS_INLINE_FUNCTION
			int hash(int q) const {
			// A simple hash by Justin Sobel
			// Thanks to Arash Partow (partow.net)
			char* fourchars = (char*)&q;
			int hash = 1315423911;
			for (int i=0; i<4; fourchars++, i++) {
			hash ^= ((hash<<5) + *fourchars + (hash >> 2));
			}
			return hash;
			}

			KOKKOS_INLINE_FUNCTION
			void operator () (const int i, int& lsum) const {
			//This is a silly function which generates 10 hashes
			// then checks for collisions
			int a = hash(i)%64;
			int b = hash(i*3)%64;
			int c = hash(i*5)%64;
			int d = hash(i*7)%64;
			int e = hash(i*11)%64;
			int f = hash(i*17)%64;
			int g = hash(i*23)%64;
			int h = hash(i*29)%64;
			int j = hash(i*31)%64;
			int k = hash(i*37)%64;


			if (a==b) lsum++;
			if (a==c) lsum++;
			if (a==d) lsum++;
			if (a==e) lsum++;
			if (a==f) lsum++;
			if (a==g) lsum++;
			if (a==h) lsum++;
			if (a==j) lsum++;
			if (a==k) lsum++;
			if (b==c) lsum++;
			if (b==d) lsum++;
			if (b==e) lsum++;
			if (b==f) lsum++;
			if (b==g) lsum++;
			if (b==h) lsum++;
			if (b==j) lsum++;
			if (b==k) lsum++;
			if (c==d) lsum++;
			if (c==e) lsum++;
			if (c==f) lsum++;
			if (c==g) lsum++;
			if (c==h) lsum++;
			if (c==j) lsum++;
			if (c==k) lsum++;
			if (d==e) lsum++;
			if (d==f) lsum++;
			if (d==g) lsum++;
			if (d==h) lsum++;
			if (d==j) lsum++;
			if (d==k) lsum++;
			if (e==f) lsum++;
			if (e==g) lsum++;
			if (e==h) lsum++;
			if (e==j) lsum++;
			if (e==k) lsum++;
			if (f==g) lsum++;
			if (f==h) lsum++;
			if (f==j) lsum++;
			if (f==k) lsum++;
			if (g==h) lsum++;
			if (g==j) lsum++;
			if (g==k) lsum++;
			if (h==j) lsum++;
			if (h==k) lsum++;
			if (j==k) lsum++;
			}



			};

			int main (int argc, char* argv[]) {
			Kokkos::initialize (argc, argv);
			const int n = 10000;

			// Compute and count hash collisions in
			// parallel, using Kokkos.
			// This is not really a useful algorithm, but it demonstrates the
			// LaunchBounds functionality
			int sum1 = 0;
			int sum2 = 0;

			//Without LaunchBounds, the kernel uses 56 registers
			Kokkos::parallel_reduce (n, collision (), sum1);

			//With LaunchBounds, we can reduce the register usage to 32
			Kokkos::parallel_reduce (Kokkos::RangePolicy<Kokkos::LaunchBounds<512,4>>(0,n), collision (), sum2);

			printf ("Number of collisions, "
			"computed in parallel, is %i\n", sum1);

			if (sum1 != sum2) {
			printf( "Uh-oh! Results do not match\n");
			return -1;
			}

			Kokkos::finalize();


			return 0;
			}

lammps/lib/kokkos/example/tutorial/launch_bounds/launch_bounds_reduce.cppdd67989c7675master

launch_bounds_reduce.cppView Options

lammps/lib/kokkos/example/tutorial/launch_bounds/launch_bounds_reduce.cpp
dd67989c7675master

launch_bounds_reduce.cpp
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