cuda中threadIdx、blockIdx、blockDim和gridDim的使用

threadIdx是一个uint3类型，表示一个线程的索引。

blockIdx是一个uint3类型，表示一个线程块的索引，一个线程块中通常有多个线程。

blockDim是一个dim3类型，表示线程块的大小。

gridDim是一个dim3类型，表示网格的大小，一个网格中通常有多个线程块。

下面这张图比较清晰的表示的几个概念的关系：

cuda 通过<<< >>>符号来分配索引线程的方式，我知道的一共有15种索引方式。

下面程序展示了这15种索引方式：

#include "cuda_runtime.h"
#include "device_launch_parameters.h"

#include <stdio.h>
#include <stdlib.h>
#include <iostream>

using namespace std;

//thread 1D
__global__ void testThread1(int *c, const int *a, const int *b)
{
    int i = threadIdx.x;
    c[i] = b[i] - a[i];
}

//thread 2D
__global__ void testThread2(int *c, const int *a, const int *b)
{
    int i = threadIdx.x + threadIdx.y*blockDim.x;
    c[i] = b[i] - a[i];
}

//thread 3D
__global__ void testThread3(int *c, const int *a, const int *b)
{
    int i = threadIdx.x + threadIdx.y*blockDim.x + threadIdx.z*blockDim.x*blockDim.y;
    c[i] = b[i] - a[i];
}

//block 1D
__global__ void testBlock1(int *c, const int *a, const int *b)
{
    int i = blockIdx.x;
    c[i] = b[i] - a[i];
}

//block 2D
__global__ void testBlock2(int *c, const int *a, const int *b)
{
    int i = blockIdx.x + blockIdx.y*gridDim.x;
    c[i] = b[i] - a[i];
}

//block 3D
__global__ void testBlock3(int *c, const int *a, const int *b)
{
    int i = blockIdx.x + blockIdx.y*gridDim.x + blockIdx.z*gridDim.x*gridDim.y;
    c[i] = b[i] - a[i];
}

//block-thread 1D-1D
__global__ void testBlockThread1(int *c, const int *a, const int *b)
{
    int i = threadIdx.x + blockDim.x*blockIdx.x;
    c[i] = b[i] - a[i];
}

//block-thread 1D-2D
__global__ void testBlockThread2(int *c, const int *a, const int *b)
{
    int threadId_2D = threadIdx.x + threadIdx.y*blockDim.x;
    int i = threadId_2D+ (blockDim.x*blockDim.y)*blockIdx.x;
    c[i] = b[i] - a[i];
}

//block-thread 1D-3D
__global__ void testBlockThread3(int *c, const int *a, const int *b)
{
    int threadId_3D = threadIdx.x + threadIdx.y*blockDim.x + threadIdx.z*blockDim.x*blockDim.y;
    int i = threadId_3D + (blockDim.x*blockDim.y*blockDim.z)*blockIdx.x;
    c[i] = b[i] - a[i];
}

//block-thread 2D-1D
__global__ void testBlockThread4(int *c, const int *a, const int *b)
{
    int blockId_2D = blockIdx.x + blockIdx.y*gridDim.x;
    int i = threadIdx.x + blockDim.x*blockId_2D;
    c[i] = b[i] - a[i];
}

//block-thread 3D-1D
__global__ void testBlockThread5(int *c, const int *a, const int *b)
{
    int blockId_3D = blockIdx.x + blockIdx.y*gridDim.x + blockIdx.z*gridDim.x*gridDim.y;
    int i = threadIdx.x + blockDim.x*blockId_3D;
    c[i] = b[i] - a[i];
}

//block-thread 2D-2D
__global__ void testBlockThread6(int *c, const int *a, const int *b)
{
    int threadId_2D = threadIdx.x + threadIdx.y*blockDim.x;
    int blockId_2D = blockIdx.x + blockIdx.y*gridDim.x;
    int i = threadId_2D + (blockDim.x*blockDim.y)*blockId_2D;
    c[i] = b[i] - a[i];
}

//block-thread 2D-3D
__global__ void testBlockThread7(int *c, const int *a, const int *b)
{
    int threadId_3D = threadIdx.x + threadIdx.y*blockDim.x + threadIdx.z*blockDim.x*blockDim.y;
    int blockId_2D = blockIdx.x + blockIdx.y*gridDim.x;
    int i = threadId_3D + (blockDim.x*blockDim.y*blockDim.z)*blockId_2D;
    c[i] = b[i] - a[i];
}

//block-thread 3D-2D
__global__ void testBlockThread8(int *c, const int *a, const int *b)
{
    int threadId_2D = threadIdx.x + threadIdx.y*blockDim.x;
    int blockId_3D = blockIdx.x + blockIdx.y*gridDim.x + blockIdx.z*gridDim.x*gridDim.y;
    int i = threadId_2D + (blockDim.x*blockDim.y)*blockId_3D;
    c[i] = b[i] - a[i];
}

//block-thread 3D-3D
__global__ void testBlockThread9(int *c, const int *a, const int *b)
{
    int threadId_3D = threadIdx.x + threadIdx.y*blockDim.x + threadIdx.z*blockDim.x*blockDim.y;
    int blockId_3D = blockIdx.x + blockIdx.y*gridDim.x + blockIdx.z*gridDim.x*gridDim.y;
    int i = threadId_3D + (blockDim.x*blockDim.y*blockDim.z)*blockId_3D;
    c[i] = b[i] - a[i];
}


void addWithCuda(int *c, const int *a, const int *b, unsigned int size)
{
    int *dev_a = 0;
    int *dev_b = 0;
    int *dev_c = 0;

    cudaSetDevice(0);

    cudaMalloc((void**)&dev_c, size * sizeof(int));
    cudaMalloc((void**)&dev_a, size * sizeof(int));
    cudaMalloc((void**)&dev_b, size * sizeof(int));

    cudaMemcpy(dev_a, a, size * sizeof(int), cudaMemcpyHostToDevice);
    cudaMemcpy(dev_b, b, size * sizeof(int), cudaMemcpyHostToDevice);

    //testThread1<<<1, size>>>(dev_c, dev_a, dev_b);

    //uint3 s;s.x = size/5;s.y = 5;s.z = 1;
    //testThread2 <<<1,s>>>(dev_c, dev_a, dev_b);

    //uint3 s; s.x = size / 10; s.y = 5; s.z = 2;
    //testThread3<<<1, s >>>(dev_c, dev_a, dev_b);

    //testBlock1<<<size,1 >>>(dev_c, dev_a, dev_b);

    //uint3 s; s.x = size / 5; s.y = 5; s.z = 1;
    //testBlock2<<<s, 1 >>>(dev_c, dev_a, dev_b);

    //uint3 s; s.x = size / 10; s.y = 5; s.z = 2;
    //testBlock3<<<s, 1 >>>(dev_c, dev_a, dev_b);

    //testBlockThread1<<<size/10, 10>>>(dev_c, dev_a, dev_b);

    //uint3 s1; s1.x = size / 100; s1.y = 1; s1.z = 1;
    //uint3 s2; s2.x = 10; s2.y = 10; s2.z = 1;
    //testBlockThread2 << <s1, s2 >> >(dev_c, dev_a, dev_b);

    //uint3 s1; s1.x = size / 100; s1.y = 1; s1.z = 1;
    //uint3 s2; s2.x = 10; s2.y = 5; s2.z = 2;
    //testBlockThread3 << <s1, s2 >> >(dev_c, dev_a, dev_b);

    //uint3 s1; s1.x = 10; s1.y = 10; s1.z = 1;
    //uint3 s2; s2.x = size / 100; s2.y = 1; s2.z = 1;
    //testBlockThread4 << <s1, s2 >> >(dev_c, dev_a, dev_b);

    //uint3 s1; s1.x = 10; s1.y = 5; s1.z = 2;
    //uint3 s2; s2.x = size / 100; s2.y = 1; s2.z = 1;
    //testBlockThread5 << <s1, s2 >> >(dev_c, dev_a, dev_b);

    //uint3 s1; s1.x = size / 100; s1.y = 10; s1.z = 1;
    //uint3 s2; s2.x = 5; s2.y = 2; s2.z = 1;
    //testBlockThread6 << <s1, s2 >> >(dev_c, dev_a, dev_b);

    //uint3 s1; s1.x = size / 100; s1.y = 5; s1.z = 1;
    //uint3 s2; s2.x = 5; s2.y = 2; s2.z = 2;
    //testBlockThread7 << <s1, s2 >> >(dev_c, dev_a, dev_b);

    //uint3 s1; s1.x = 5; s1.y = 2; s1.z = 2;
    //uint3 s2; s2.x = size / 100; s2.y = 5; s2.z = 1;
    //testBlockThread8 <<<s1, s2 >>>(dev_c, dev_a, dev_b);

    uint3 s1; s1.x = 5; s1.y = 2; s1.z = 2;
    uint3 s2; s2.x = size / 200; s2.y = 5; s2.z = 2;
    testBlockThread9<<<s1, s2 >>>(dev_c, dev_a, dev_b);

    cudaMemcpy(c, dev_c, size*sizeof(int), cudaMemcpyDeviceToHost);

    cudaFree(dev_a);
    cudaFree(dev_b);
    cudaFree(dev_c);

    cudaGetLastError();
}


int main()
{
    const int n = 1000;

    int *a = new int[n];
    int *b = new int[n];
    int *c = new int[n];
    int *cc = new int[n];

    for (int i = 0; i < n; i++)
    {
        a[i] = rand() % 100;
        b[i] = rand() % 100;
        c[i] = b[i] - a[i];
    }

    addWithCuda(cc, a, b, n);

    FILE *fp = fopen("out.txt", "w");
    for (int i = 0; i < n; i++)
        fprintf(fp, "%d %d\n", c[i], cc[i]);
    fclose(fp);

    bool flag = true;
    for (int i = 0; i < n; i++)
    {
        if (c[i] != cc[i])
        {
            flag = false;
            break;
        }
    }

    if (flag == false)
        printf("no pass");
    else
        printf("pass");

    cudaDeviceReset();

    delete[] a;
    delete[] b;
    delete[] c;
    delete[] cc;

    getchar();
    return 0;
}

这里只保留了3D-3D方式，注释了其余14种方式，所有索引方式均测试通过。

还是能看出一些规律的：)