1.对于一个标准的3*3 均值滤波，kernel代码如下：
使用buffer/image缓冲对象
__kernel void filter(__global uchar4* inputImage, __global uchar4* outputImage, uint N) {int x = get_global_id(0);int y = get_global_id(1);int width = get_global_size(0);int height = get_global_size(1);int k = (N-1)/2;int n = N*N; //n*nif(x < k || y < k || x > width - k - 1 || y > height - k - 1) { outputImage[x + y * width] = inputImage[x + y * width];return; }uint4 finalcolor = (uint4)(0);int i,j;for(j = y - k; j <= y + k; j++) {for(i = x - k; i <= x + k; i++) { finalcolor = finalcolor + convert_uint4(inputImage[i + j * width]); } } outputImage[x + y * width] = convert_uchar4(finalcolor/n);}
__kernel void filterImg( image2d_t inputImage, __write_only image2d_t outputImage, uint N) {int x = get_global_id(0);int y = get_global_id(1);int width = get_global_size(0);int height = get_global_size(1);uint4 temp = read_imageui(inputImage, imageSampler, (int2)(x,y));int k = (N-1)/2;int n = N*N; //n*nif(x < k || y < k || x > width - k - 1 || y > height - k - 1) { write_imageui(outputImage, (int2)(x,y), temp);return; }/* k*k area */ uint4 finalcolor = (uint4)(0);int i,j;for(j = y - k; j <= y + k; j++) {for(i = x - k; i <= x + k; i++) { finalcolor = finalcolor + read_imageui(inputImage, imageSampler, (int2)(i,j)); } }finalcolor = finalcolor/n;write_imageui(outputImage, (int2)(x,y), finalcolor);}
对一个2048*2048的图像执行filter操作，
global work size = {2048, 2048, 1}, group work size = {16, 16}, 一般group work size应该为64的倍数，因为对于AMD显卡，wave是基本的硬件线程调度单位。
使用了6个GPRs，没有使用ScratchRegs,ScratchRregs是指用vedio meory来模拟GPR，但是线程执行的速度会大大降低，应尽量减少ScratchRegs的数量。
可以看到，使用image对象kernel执行时间要短，但奇怪的是各项性能参数都是buffer对象领先，除了alu busy和alu指令数目。
改为下面的kernel代码，性能会有所提高
__kernel void filter(__global uchar4* inputImage, __global uchar4* outputImage, uint N) {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 || x > width - 2 || y > height - 2) { outputImage[x + y * width] = inputImage[x + y * width];return; }uint4 finalcolor = (uint4)(0);finalcolor = finalcolor + convert_uint4(inputImage[x-1+( y-1) * width]); finalcolor = finalcolor + convert_uint4(inputImage[x+( y-1) * width]); finalcolor = finalcolor + convert_uint4(inputImage[x+1+( y-1) * width]); finalcolor = finalcolor + convert_uint4(inputImage[x-1+y * width]); finalcolor = finalcolor + convert_uint4(inputImage[x+y * width]); finalcolor = finalcolor + convert_uint4(inputImage[x+1+y * width]); finalcolor = finalcolor + convert_uint4(inputImage[x-1+( y+1) * width]); finalcolor = finalcolor + convert_uint4(inputImage[x+( y+1) * width]); finalcolor = finalcolor + convert_uint4(inputImage[x+1+( y+1) * width]);outputImage[x + y * width] = convert_uchar4(finalcolor/9);} __kernel void filter1(__global uchar4* inputImage, __global uchar4* outputImage, uint N) {int x = get_global_id(0);int y = get_global_id(1);int width = get_global_size(0);int height = get_global_size(1);int k = (N-1)/2;int n = N*N; //n*nif(x < k || y < k || x > width - k - 1 || y > height - k - 1) { outputImage[x + y * width inputImage[x + y * width];return; }// if(x==209 && y ==243)//{// printf("final color:%d,%d,%d,%d\n", finalcolor.x, finalcolor.y, finalcolor.z,finalcolor.w);// }uint4 finalcolor = (uint4)(0);int i,j;for(j = y - k; j <= y + k; j++) {for(i = x - k; i <= x + k; i++) { finalcolor = finalcolor + convert_uint4(inputImage[i + j * width]); } } outputImage[x + y * width] = convert_uchar4(finalcolor/n);} __kernel void filterImg( image2d_t inputImage, __write_only image2d_t outputImage, uint N) {int x = get_global_id(0);int y = get_global_id(1);int width = get_global_size(0);int height = get_global_size(1);uint4 temp = read_imageui(inputImage, imageSampler, (int2)(x,y));if(x < 1 || y < 1 || x > width - 2 || y > height - 2) { write_imageui(outputImage, (int2)(x,y), temp);return; }/* k*k area */ uint4 finalcolor = (uint4)(0);finalcolor = finalcolor + read_imageui(inputImage, imageSampler, (int2)(x-1,y-1)); finalcolor = finalcolor + read_imageui(inputImage, imageSampler, (int2)(x,y-1)); finalcolor = finalcolor + read_imageui(inputImage, imageSampler, (int2)(x+1,y-1)); finalcolor = finalcolor + read_imageui(inputImage, imageSampler, (int2)(x-1,y)); finalcolor = finalcolor + read_imageui(inputImage, imageSampler, (int2)(x,y)); finalcolor = finalcolor + read_imageui(inputImage, imageSampler, (int2)(x+1,y)); finalcolor = finalcolor + read_imageui(inputImage, imageSampler, (int2)(x-1,y+1)); finalcolor = finalcolor + read_imageui(inputImage, imageSampler, (int2)(x,y+1)); finalcolor = finalcolor + read_imageui(inputImage, imageSampler, (int2)(x+1,y+1));finalcolor = finalcolor/9;write_imageui(outputImage, (int2)(x,y), finalcolor);}
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