Source code that accompanies The CUDA Handbook.
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/*
*
* histogramPerGrid.cuh
*
* Implementation of histogram that uses one global atomic per pixel.
* This results in very data-dependent performance, as the hardware
* facilities for mutual exclusion contend when trying to increment
* the same histogram value concurrently.
*
* Requires: SM 1.1, for global atomics.
*
* Build with:
* nvcc -I ..\chLib --gpu-architecture sm_xx histogram.cu ..\chLib\pgm.cu -lnpp
*
* Copyright (c) 2013, 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
histogram1DPerGrid(
unsigned int *pHist,
const unsigned char *base, size_t N )
{
for ( size_t i = blockIdx.x*blockDim.x+threadIdx.x;
i < N/4;
i += blockDim.x*gridDim.x ) {
unsigned int value = ((unsigned int *) base)[i];
atomicAdd( &pHist[ value & 0xff ], 1 ); value >>= 8;
atomicAdd( &pHist[ value & 0xff ], 1 ); value >>= 8;
atomicAdd( &pHist[ value & 0xff ], 1 ); value >>= 8;
atomicAdd( &pHist[ value ] , 1 );
}
}
void
GPUhistogramPerGrid(
float *ms,
unsigned int *pHist,
const unsigned char *dptrBase, size_t dPitch,
int x, int y,
int w, int h,
dim3 threads )
{
cudaError_t status;
cudaEvent_t start = 0, stop = 0;
cuda(EventCreate( &start ) );
cuda(EventCreate( &stop ) );
cuda(EventRecord( start, 0 ) );
// histogramPerGrid<<<blocks,threads>>>( pHist, w, h );
histogram1DPerGrid<<<400, 256>>>( pHist, dptrBase, w*h );
cuda(EventRecord( stop, 0 ) );
cuda(DeviceSynchronize() );
cuda(EventElapsedTime( ms, start, stop ) );
Error:
cudaEventDestroy( start );
cudaEventDestroy( stop );
return;
}