example.cu

/* Copyright (c) 1993-2015, NVIDIA CORPORATION. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * 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.
 *  * Neither the name of NVIDIA CORPORATION nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``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.
 */
#include <cstdio>

__global__ void staticReverse(int *d, int n) {
  __shared__ int s[64];
  int t = threadIdx.x;
  int tr = n - t - 1;
  s[t] = d[t];
  __syncthreads();
  d[t] = s[tr];
}

__global__ void dynamicReverse(int *d, int n) {
  extern __shared__ int s[];
  int t = threadIdx.x;
  int tr = n - t - 1;
  s[t] = d[t];
  __syncthreads();
  d[t] = s[tr];
}

int main() {
  const int n = 64;
  int a[n], r[n], d[n];

  for (int i = 0; i < n; i++) {
    a[i] = i;
    r[i] = n - i - 1;
    d[i] = 0;
  }

  int *d_d;
  cudaMalloc((void **)d_d, n * sizeof(int));

  // run version with static shared memory
  cudaMemcpy(d_d, a, n * sizeof(int), cudaMemcpyHostToDevice);
  staticReverse<<<1, n>>>(d_d, n);
  cudaMemcpy(d, d_d, n * sizeof(int), cudaMemcpyDeviceToHost);
  for (int i = 0; i < n; i++)
    if (d[i] != r[i])
      printf("Error: d[%d]!=r[%d] (%d, %d)\n", i, i, d[i], r[i]);

  // run dynamic shared memory version
  cudaMemcpy(d_d, a, n * sizeof(int), cudaMemcpyHostToDevice);
  dynamicReverse<<<1, n, n * sizeof(int)>>>(d_d, n);
  cudaMemcpy(d, d_d, n * sizeof(int), cudaMemcpyDeviceToHost);
  for (int i = 0; i < n; i++)
    if (d[i] != r[i])
      printf("Error: d[%d]!=r[%d] (%d, %d)\n", i, i, d[i], r[i]);
}