CUDA线程分配<<<>>>

在cuda中，blockDim表示一个块中线程的维度信息，例如blockDim（2,1,1）代表一个块中有2个thread，gridDim表示一个网格中块的维度。

下面给出一个示例程序，这个程序来自CUDA C语言编程中文译本，如有侵权，联系删除。

#include "../common/common.h"#include <cuda_runtime.h>#include <stdio.h>/* * Display the dimensionality of a thread block and grid from the host and * device. */__global__ void checkIndex(void){    printf("threadIdx:(%d, %d, %d)\n", threadIdx.x, threadIdx.y, threadIdx.z);    printf("---blockIdx:(%d, %d, %d)\n", blockIdx.x, blockIdx.y, blockIdx.z);    printf("------blockDim:(%d, %d, %d)\n", blockDim.x, blockDim.y, blockDim.z);    printf("---------gridDim:(%d, %d, %d)\n", gridDim.x, gridDim.y, gridDim.z);}int main(int argc, char **argv){    // define total data element    int nElem = 6;    // define grid and block structure    dim3 block(3);    dim3 grid((nElem + block.x - 1) / block.x);    // check grid and block dimension from host side    printf("grid.x %d, grid.y %d, grid.z %d,\n", grid.x, grid.y, grid.z);    printf("block.x %d, block.y %d, block.z %d,\n", block.x, block.y, block.z);    // check grid and block dimension from device side    checkIndex<<<grid, block>>>();    // reset device before you leave    CHECK(cudaDeviceReset());    return(0);}

编译与运行：

-bash-4.1$ nvcc -o a checkDimension.cu-bash-4.1$ ./agrid.x 2, grid.y 1, grid.z 1,block.x 3, block.y 1, block.z 1,threadIdx:(0, 0, 0)threadIdx:(1, 0, 0)threadIdx:(2, 0, 0)threadIdx:(0, 0, 0)threadIdx:(1, 0, 0)threadIdx:(2, 0, 0)---blockIdx:(1, 0, 0)---blockIdx:(1, 0, 0)---blockIdx:(1, 0, 0)---blockIdx:(0, 0, 0)---blockIdx:(0, 0, 0)---blockIdx:(0, 0, 0)------blockDim:(3, 1, 1)------blockDim:(3, 1, 1)------blockDim:(3, 1, 1)------blockDim:(3, 1, 1)------blockDim:(3, 1, 1)------blockDim:(3, 1, 1)---------gridDim:(2, 1, 1)---------gridDim:(2, 1, 1)---------gridDim:(2, 1, 1)---------gridDim:(2, 1, 1)---------gridDim:(2, 1, 1)---------gridDim:(2, 1, 1)-bash-4.1$ 

为了更加浅显地展示grid，block和thread之间的关系，我画了几个图：