作为初学者一直，经过多次的上网搜索你一定会看到迈克老狼的向量加法的示例，不知道你是否和我一样，刚开始并不是很准确的知道他的add.cl写的代码的意思，源码如下：

#pragma OPENCL EXTENSION cl_amd_printf : enable
__kernel void vecadd(__global const float* a, __global const float* b, __global float* c){int x = get_global_id(0);int y = get_global_id(1);int width = get_global_size(0);int height = get_global_size(1);if(x == 1 && y ==1)printf("%d, %d,%d,%d,%d,%d\n",get_local_size(0),get_local_size(1),get_local_id(0),get_local_id(1),get_group_id(0),get_group_id(1));c[x + y * width] = a[x + y * width] + b[x + y * width];}我们在k

这里面我把二维的这些值全部罗列出来如下：

int idx = get_global_id(0);
int idy = get_global_id(1);

uint wiWidth = get_global_size(0);
uint wiHeight = get_global_size(1);

uint gix_t = get_group_id(0);
uint giy_t = get_group_id(1);

uint num_of_blocks_x = get_num_groups(0);
uint num_of_blocks_y = get_num_groups(1);

uint lix = get_local_id(0);
uint liy = get_local_id(1);

你会奇怪为什么他的add.cl优化会这么写：

c[x + y * width] = a[x + y * width] + b[x + y * width];

下面进行分析：

add.cpp关键的代码部分如下（只罗列出部分代码）：

#define width 8//256
#define height 16//256
#define NWITEMS  width*height//262144size_t globalThreads[] = {width, height};size_t localx, localy;localx = 2;localy = 4;size_t localThreads[] = {localx, localy};clEnqueueNDRangeKernel( queue,kernel,2,NULL,globalThreads,localThreads, 0, NULL, &ev);

我自己的add.cl代码如下（里面添加啦打印，以便我们可以看出结果）：

 　 int idx = get_global_id(0);int idy = get_global_id(1);uint wiWidth  = get_global_size(0);uint wiHeight  = get_global_size(1);printf("Magnum Global idx = %d, idy = %d, sizeX =%d,sizeY =%d\n",idx,idy,wiWidth,wiHeight);uint gix_t = get_group_id(0); uint giy_t = get_group_id(1);    uint num_of_blocks_x = get_num_groups(0); uint num_of_blocks_y = get_num_groups(1); printf("Magnum Group idx = %d, idy = %d, blockX=%d,blockY=%d\n",gix_t,gix_t,num_of_blocks_x,num_of_blocks_y);
uint lix = get_local_id(0); uint liy = get_local_id(1);uint LocalX = get_local_size(0);uint LocalY = get_local_size(1);printf("Magnum Local idx = %d, idy = %d, localX=%d,localY=%d\n\n",lix,liy,LocalX,LocalY);

输出的结果如下：

Magnum Global idx = 0, idy = 0, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 1, idy = 0, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 0, idy = 1, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 1, idy = 1, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 0, idy = 2, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 1, idy = 2, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 0, idy = 3, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 1, idy = 3, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 2, idy = 0, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 3, idy = 0, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 2, idy = 1, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 3, idy = 1, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 2, idy = 2, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 3, idy = 2, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 2, idy = 3, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 3, idy = 3, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 4, idy = 0, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 5, idy = 0, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 4, idy = 1, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 5, idy = 1, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 4, idy = 2, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 5, idy = 2, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 4, idy = 3, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 5, idy = 3, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 6, idy = 0, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 7, idy = 0, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 6, idy = 1, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 7, idy = 1, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 6, idy = 2, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 7, idy = 2, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 6, idy = 3, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 7, idy = 3, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 0, idy = 4, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 1, idy = 4, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 0, idy = 5, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 1, idy = 5, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 0, idy = 6, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 1, idy = 6, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 0, idy = 7, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 1, idy = 7, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 2, idy = 4, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 3, idy = 4, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 2, idy = 5, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 3, idy = 5, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 2, idy = 6, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 3, idy = 6, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 2, idy = 7, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 3, idy = 7, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 4, idy = 4, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 5, idy = 4, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 4, idy = 5, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 5, idy = 5, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 4, idy = 6, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 5, idy = 6, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 4, idy = 7, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 5, idy = 7, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 6, idy = 4, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 7, idy = 4, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 6, idy = 5, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 7, idy = 5, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 6, idy = 6, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 7, idy = 6, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 6, idy = 7, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 7, idy = 7, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 0, idy = 8, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 1, idy = 8, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 0, idy = 9, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 1, idy = 9, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 0, idy = 10, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 1, idy = 10, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 0, idy = 11, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 1, idy = 11, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 2, idy = 8, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 3, idy = 8, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 2, idy = 9, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 3, idy = 9, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 2, idy = 10, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 3, idy = 10, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 2, idy = 11, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 3, idy = 11, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 4, idy = 8, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 5, idy = 8, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 4, idy = 9, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 5, idy = 9, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 4, idy = 10, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 5, idy = 10, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 4, idy = 11, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 5, idy = 11, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 6, idy = 8, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 7, idy = 8, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 6, idy = 9, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 7, idy = 9, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 6, idy = 10, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 7, idy = 10, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 6, idy = 11, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 7, idy = 11, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 0, idy = 12, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 1, idy = 12, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 0, idy = 13, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 1, idy = 13, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 0, idy = 14, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 1, idy = 14, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 0, idy = 15, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 1, idy = 15, sizeX =8,sizeY =16
Magnum Group idx = 0, idy = 0, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 2, idy = 12, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 3, idy = 12, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 2, idy = 13, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 3, idy = 13, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 2, idy = 14, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 3, idy = 14, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 2, idy = 15, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 3, idy = 15, sizeX =8,sizeY =16
Magnum Group idx = 1, idy = 1, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 4, idy = 12, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 5, idy = 12, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 4, idy = 13, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 5, idy = 13, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 4, idy = 14, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 5, idy = 14, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 4, idy = 15, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 5, idy = 15, sizeX =8,sizeY =16
Magnum Group idx = 2, idy = 2, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4Magnum Global idx = 6, idy = 12, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 0, localX=2,localY=4Magnum Global idx = 7, idy = 12, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 0, localX=2,localY=4Magnum Global idx = 6, idy = 13, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 1, localX=2,localY=4Magnum Global idx = 7, idy = 13, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 1, localX=2,localY=4Magnum Global idx = 6, idy = 14, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 2, localX=2,localY=4Magnum Global idx = 7, idy = 14, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 2, localX=2,localY=4Magnum Global idx = 6, idy = 15, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 0, idy = 3, localX=2,localY=4Magnum Global idx = 7, idy = 15, sizeX =8,sizeY =16
Magnum Group idx = 3, idy = 3, blockX=4,blockY=4
Magnum Local idx = 1, idy = 3, localX=2,localY=4

View Code

从从这个结果首先能说明几个问题：

首先我们在：

  1. clEnqueueNDRangeKernel( queue, kernel, 2, NULL, globalThreads, localThreads, 0, NULL, &ev); 设置维度是2，否则add.cl中所有类似get_local_size(1)将只会返回一。
  2. 设置GlobaThreads 和 LocalThreads 不一定是 GlobalThreads= {8, 8}; 也可以不相等，LocalThreads也是一样。
  3. 理解opencl中的内存分布可以理解为二维数组，而且内存寻址的方向就像是：左上角（0，0）为原点，一行一行的扫描下去。
  4. WorkGroup的大小，目前我认为X，Y可以分开来理解（后面若发现错误我会及时改正） WorkGroup number(x) = GlobalThread(x)/LocalThread(x).
  5. 最小的单位是LocalX * LocalY, 然后用总的GlobalThreads按照这个单位进行分割成一个一个的组。每个二维的小单位还是一行一行的扫描过去的。目前我们的这个是8*16，你会发现总的Thread也是8*16，对应的每一个线程执行一次加法操作，有人会问可不可以不用这么多呢,用4*16个Threads,每个线程里面做两次加法动作，其实是可以的，这个原则是根据你的具体的Device来说的，当前我们说的是Device是GPU，比如你的GPU当前支持最大的线程数是1024*1024，这种情况，你不用多的，而是用少的线程来做，会降低你的效率，你需要尽可能的让Device满负荷工作这样才能达到提高运算速度。

继续分析为什么 NDRange改成二维的之后,add.cl变成：

c[x + y * width] = a[x + y * width] + b[x + y * width];

因为在CPU端每个 C[8*16],通过打印可以在这里C[x+y*width]，x 最大是7，width是8,y最大是17，只有这样才能做完所有的向量相加。

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