OpenCL 学习step by step (5) 使用二维NDRange workgroup
OpenCL 学习step by step (5) 使用二维NDRange workgroup<div class="postbody"><div id="cnblogs_post_body"> 在本教程中，我们使用二维NDRange来设置workgroup，这样在opencl中，workitme的组织形式是二维的，Kernel中 的代码也要做相应的改变，我们先看一下clEnqueueNDRangeKernel函数的变化。首先我们指定了workgroup size为localx*localy,通常这个值为64的倍数，但最好不要超过256。
//执行kernel,Range用2维，work itmes size为width*height,
cl_event ev;
size_t globalThreads[] = {width, height};
size_t localx, localy;
if(width/8 > 4)
localx = 16;
else if(width < 8)
localx = width;
else localx = 8;
if(height/8 > 4)
localy = 16;
else if (height < 8)
localy = height;
else localy = 8;
size_t localThreads[] = {localx, localy}; // localx*localy应该是64的倍数
printf(&quot;global_work_size =(%d,%d), local_work_size=(%d, %d)\n&quot;,width,height,localx,localy);
clTimer.Reset();
clTimer.Start();
clEnqueueNDRangeKernel( queue,
kernel,
2,
NULL,
globalThreads,
localThreads, 0, NULL, &ev);
注意：在上面代码中，定义global threads以及local threads数量，都是通过二维数组的方式进行的。
新的Kernel代码如下：
<div style="border-bottom: silver 1px solid; text-align: left; border-left: silver 1px solid; padding-bottom: 4px; line-height: 12pt; background-color: #f4f4f4; margin: 20px 0px 10px; padding-left: 4px; width: 97.5%; padding-right: 4px; font-family: &#39;Courier New&#39;, courier, monospace; direction: ltr; max-height: 200px; font-size: 8pt; overflow: auto; border-top: silver 1px solid; cursor: text; border-right: silver 1px solid; padding-top: 4px" id="codeSnippetWrapper"> #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(&quot;%d, %d,%d,%d,%d,%d\n&quot;,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 = a + b;
}
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