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/*
*
* reduction2WarpSynchronous.cuh
*
* Header for warp synchronous formulation of reduction.
*
* Copyright (c) 2011-2012, Archaea Software, LLC.
* All rights reserved.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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 THE
* COPYRIGHT OWNER OR 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.
*
*/
__global__ void
Reduction2_kernel( int *out, const int *in, size_t N )
{
extern __shared__ int sPartials[];
int sum = 0;
const int tid = threadIdx.x;
for ( size_t i = blockIdx.x*blockDim.x + tid;
i < N;
i += blockDim.x*gridDim.x ) {
sum += in[i];
}
sPartials[tid] = sum;
__syncthreads();
for ( int activeThreads = blockDim.x>>1;
activeThreads > 32;
activeThreads >>= 1 ) {
if ( tid < activeThreads ) {
sPartials[tid] += sPartials[tid+activeThreads];
}
__syncthreads();
}
if ( threadIdx.x < 32 ) {
volatile int *wsSum = sPartials;
if ( blockDim.x > 32 ) wsSum[tid] += wsSum[tid + 32];
wsSum[tid] += wsSum[tid + 16];
wsSum[tid] += wsSum[tid + 8];
wsSum[tid] += wsSum[tid + 4];
wsSum[tid] += wsSum[tid + 2];
wsSum[tid] += wsSum[tid + 1];
if ( tid == 0 ) {
volatile int *wsSum = sPartials;
out[blockIdx.x] = wsSum[0];
}
}
}
void
Reduction2( int *answer, int *partial,
const int *in, size_t N,
int numBlocks, int numThreads )
{
Reduction2_kernel<<<
numBlocks, numThreads, numThreads*sizeof(int)>>>(
partial, in, N );
Reduction2_kernel<<<
1, numThreads, numThreads*sizeof(int)>>>(
answer, partial, numBlocks );
}