我正在尝试使用cudaMemcpy3D
来传输动态分配的3d矩阵(张量)。 Tensor被分配为连续的内存块(参见下面的代码)。我尝试了cudaExtent
和cudaMemcpy3DParms
的各种组合,但元素的顺序混淆了。我创建了以下示例来演示此问题:
#include <stdio.h>
int ***alloc_tensor(int Nx, int Ny, int Nz) {
int i, j;
int ***tensor;
tensor = (int ***) malloc((size_t) (Nx * sizeof(int **)));
tensor[0] = (int **) malloc((size_t) (Nx * Ny * sizeof(int *)));
tensor[0][0] = (int *) malloc((size_t) (Nx * Ny * Nz * sizeof(int)));
for(j = 1; j < Ny; j++)
tensor[0][j] = tensor[0][j-1] + Nz;
for(i = 1; i < Nx; i++) {
tensor[i] = tensor[i - 1] + Ny;
tensor[i][0] = tensor[i - 1][0] + Ny * Nz;
for(j = 1; j < Ny; j++)
tensor[i][j] = tensor[i][j - 1] + Nz;
}
return tensor;
}
__global__ void kernel(cudaPitchedPtr tensor, int Nx, int Ny, int Nz) {
int i, j, k;
char *tensorslice;
int *tensorrow;
for (i = 0; i < Nx; i++) {
for (j = 0; j < Ny; j++) {
for (k = 0; k < Nz; k++) {
tensorslice = ((char *)tensor.ptr) + k * tensor.pitch * Nx;
tensorrow = (int *)(tensorslice + i * tensor.pitch);
printf("d_tensor[%d][%d][%d] = %d\n", i, j, k, tensorrow[j]);
}
}
}
}
int main() {
int i, j, k, value = 0;
int Nx = 2, Ny = 6, Nz = 4;
int ***h_tensor;
struct cudaPitchedPtr d_tensor;
h_tensor = alloc_tensor(Nx, Ny, Nz);
cudaMalloc3D(&d_tensor, make_cudaExtent(Nx * sizeof(int), Ny, Nz));
for(i = 0; i < Nx; i++) {
for(j = 0; j < Ny; j++) {
for(k = 0; k < Nz; k++) {
h_tensor[i][j][k] = value++;
printf("h_tensor[%d][%d][%d] = %d\n", i, j, k, h_tensor[i][j][k]);
}
}
}
cudaMemcpy3DParms cpy = { 0 };
cpy.srcPtr = make_cudaPitchedPtr(h_tensor[0][0], Nx * sizeof(int), Ny, Nz);
cpy.dstPtr = d_tensor;
cpy.extent = make_cudaExtent(Nx * sizeof(int), Ny, Nz);
cpy.kind = cudaMemcpyHostToDevice;
cudaMemcpy3D(&cpy);
kernel<<<1, 1>>>(d_tensor, Nx, Ny, Nz);
// ... clean-up
}
主变量(h_tensor
)和设备(d_tensor
)的输出不同,看起来像
h_tensor[0][0][0] = 0
h_tensor[0][0][1] = 1
h_tensor[0][0][2] = 2
h_tensor[0][0][3] = 3
h_tensor[0][1][0] = 4
h_tensor[0][1][1] = 5
h_tensor[0][1][2] = 6
...
d_tensor[0][0][0] = 0
d_tensor[0][0][1] = 12
d_tensor[0][0][2] = 24
d_tensor[0][0][3] = 36
d_tensor[0][1][0] = 1
d_tensor[0][1][1] = 13
d_tensor[0][1][2] = 25
...
我做错了什么?使用cudaMemcpy3D
的正确方法是什么?
答案 0 :(得分:3)
cudaMemcpy3D
行会引发错误。这是由于下面的第2项。 (我怀疑用于生成输出的代码与您在此处显示的代码不同,但这只是猜测。)您对make_cudaPitchedPtr
的使用不正确:
cpy.srcPtr = make_cudaPitchedPtr(h_tensor[0][0], Nx * sizeof(int), Ny, Nz);
查看API文档。以这种方式制作CUDA倾斜指针在2D和3D之间没有区别。因此,正如您所做的那样,传递3个不同的维度是没有意义的。而是这样做:
cpy.srcPtr = make_cudaPitchedPtr(h_tensor[0][0], Nx * sizeof(int), Nx, Ny);
我发现的其余问题归因于对C中3维的错误理解。乘法下标数组的最后一个下标是快速变化的维度,即它是内存中相邻值占据相邻索引的维度值。由于这个原因,你在第三维中使用Z会让我感到困惑。您的主机分配在第一个下标位置使用Nx
,但您的设备索引不匹配。显然有多种方法可以解决这个问题。如果您不喜欢我的安排,您可以更改它,但主机和设备索引必须匹配。
无论如何,以下代码修改对我有用:
#include <stdio.h>
int ***alloc_tensor(int Nx, int Ny, int Nz) {
int i, j;
int ***tensor;
tensor = (int ***) malloc((size_t) (Nx * sizeof(int **)));
tensor[0] = (int **) malloc((size_t) (Nx * Ny * sizeof(int *)));
tensor[0][0] = (int *) malloc((size_t) (Nx * Ny * Nz * sizeof(int)));
for(j = 1; j < Ny; j++)
tensor[0][j] = tensor[0][j-1] + Nz;
for(i = 1; i < Nx; i++) {
tensor[i] = tensor[i - 1] + Ny;
tensor[i][0] = tensor[i - 1][0] + Ny * Nz;
for(j = 1; j < Ny; j++)
tensor[i][j] = tensor[i][j - 1] + Nz;
}
return tensor;
}
__global__ void kernel(cudaPitchedPtr tensor, int Nx, int Ny, int Nz) {
int i, j, k;
char *tensorslice;
int *tensorrow;
for (i = 0; i < Nx; i++) {
for (j = 0; j < Ny; j++) {
for (k = 0; k < Nz; k++) {
tensorslice = ((char *)tensor.ptr) + k * tensor.pitch * Ny;
tensorrow = (int *)(tensorslice + j * tensor.pitch);
printf("d_tensor[%d][%d][%d] = %d\n", i, j, k, tensorrow[i]);
}
}
}
}
int main() {
int i, j, k, value = 0;
int Nx = 2, Ny = 6, Nz = 4;
int ***h_tensor;
struct cudaPitchedPtr d_tensor;
h_tensor = alloc_tensor(Nz, Ny, Nx);
cudaMalloc3D(&d_tensor, make_cudaExtent(Nx * sizeof(int), Ny, Nz));
for(i = 0; i < Nx; i++) {
for(j = 0; j < Ny; j++) {
for(k = 0; k < Nz; k++) {
h_tensor[k][j][i] = value++;
//printf("h_tensor[%d][%d][%d] = %d\n", i, j, k, h_tensor[i][j][k]);
}
}
}
for(i = 0; i < Nx; i++) {
for(j = 0; j < Ny; j++) {
for(k = 0; k < Nz; k++) {
//h_tensor[i][j][k] = value++;
printf("h_tensor[%d][%d][%d] = %d\n", i, j, k, h_tensor[k][j][i]);
}
}
}
cudaMemcpy3DParms cpy = { 0 };
cpy.srcPtr = make_cudaPitchedPtr(h_tensor[0][0], Nx * sizeof(int), Nx, Ny);
cpy.dstPtr = d_tensor;
cpy.extent = make_cudaExtent(Nx * sizeof(int), Ny, Nz);
cpy.kind = cudaMemcpyHostToDevice;
cudaMemcpy3D(&cpy);
kernel<<<1, 1>>>(d_tensor, Nx, Ny, Nz);
cudaDeviceSynchronize();
// ... clean-up
}