Question

我尝试了以下使用curand生成随机数的程序。当要生成的元素数量（变量n）是奇数时，如下面的9849，我在curandGenerateNormal的行上出错了。偶数个元素没有这个问题。这是什么原因？

#include <curand.h>
#include <iostream>
#include <cstdlib>
using namespace std;

#define CHKcuda(x) do {                             \
  cudaError_t y = (x);                              \
  if (y != cudaSuccess) {                           \
    cout << __LINE__ << ": " << y << endl; exit(1); \
  }                                                 \
} while(0)
#define CHKcurand(x) do {                           \
  curandStatus_t y = (x);                           \
  if (y != CURAND_STATUS_SUCCESS) {                 \
    cout << __LINE__ << ": " << y << endl; exit(1); \
  }                                                 \
} while(0)

int main(int argc, char** argv) {
  curandGenerator_t g_randgen;
  float *ptr, *h_ptr;
  int n;
  if (argc > 1) {
    n = atoi(argv[1]);
  }  
  CHKcurand(curandCreateGenerator(&g_randgen, CURAND_RNG_PSEUDO_DEFAULT));
  CHKcuda(cudaMalloc((void**)&ptr, n * sizeof(float)));
  CHKcurand(curandGenerateNormal(g_randgen, ptr, n, 0, 0.1));
  h_ptr = static_cast<float*>(malloc(sizeof(float) * n));
  CHKcuda(cudaMemcpy(h_ptr, ptr, sizeof(float) * n, cudaMemcpyDeviceToHost));
  CHKcuda(cudaDeviceSynchronize());
  for (int i = 0; i < 5; i++) {
    cout << h_ptr[i] << ", ";
  }
  cout << endl;
  return 0;
}

编辑：

我检查了生成函数的返回值。错误代码的定义如下：

CURAND_STATUS_LENGTH_NOT_MULTIPLE = 105, ///< Length requested is not a multple of dimension

但是，在文档中它只说生成准随机数时，元素的数量必须是维度的倍数。那么为什么它会影响这里的伪随机数生成呢？或者我用来创建生成器（CURAND_RNG_PSEUDO_DEFAULT）的参数实际创建了一个准随机数生成器？而且，维度的确切价值是什么，我在哪里可以找到它？

Answer 1

通常，正常生成函数（例如curandGenerateNormal，curandGenerateLogNormal等）要求伪随机RNG的请求点数为2的倍数。

这是documented：

curandStatus_t CURANDAPI curandGenerateNormal ( curandGenerator_t generator, float* outputPtr, size_t n, float  mean, float  stddev ) 

Generate normally distributed doubles. 


Parameters 
generator- Generator to use outputPtr- Pointer to device memory to store CUDA-generated results, or Pointer to host memory to store CPU-generated results n- Number of floats to generate mean- Mean of normal distribution stddev- Standard deviation of normal distribution

Returns


•CURAND_STATUS_NOT_INITIALIZED if the generator was never created 
•CURAND_STATUS_PREEXISTING_FAILURE if there was an existing error from a previous kernel launch 
•CURAND_STATUS_LAUNCH_FAILURE if the kernel launch failed for any reason 
•CURAND_STATUS_LENGTH_NOT_MULTIPLE if the number of output samples is not a multiple of the quasirandom dimension, or is not a multiple of two for pseudorandom generators 
•CURAND_STATUS_SUCCESS if the results were generated successfully

例如，

curandGenerateUniform没有此限制。

curand生成器在奇数个元素上失败

1 个答案: