CUDA内核 - 嵌套for循环 [英] CUDA kernel - nested for loop
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问题描述
Hello
我试图写一个CUDA内核来执行下面的代码。
Hello I'm trying to write a CUDA kernel to perform the following piece of code.
for (n = 0; n < (total-1); n++)
{
a = values[n];
for ( i = n+1; i < total ; i++)
{
b = values[i] - a;
c = b*b;
if( c < 10)
newvalues[i] = c;
}
}
这是我目前的状态,似乎给了正确的结果?有人知道我做错了什么。欢呼
This is what I have currently, but it does not seem to be giving the correct results? does anyone know what I'm doing wrong. Cheers
__global__ void calc(int total, float *values, float *newvalues){
float a,b,c;
int idx = blockIdx.x * blockDim.x + threadIdx.x;
for (int n = idx; n < (total-1); n += blockDim.x*gridDim.x){
a = values[n];
for(int i = n+1; i < total; i++){
b = values[i] - a;
c = b*b;
if( c < 10)
newvalues[i] = c;
}
}
推荐答案
在2D中实现此问题,并使用2D线程块启动内核。在x和y维度中的总线数将等于总计。内核代码应如下所示:
Realize this problem in 2D and launch your kernel with 2D thread blocks. The total number of threads in x and y dimension will be equal to total . The kernel code should look like this:
__global__ void calc(float *values, float *newvalues, int total){
float a,b,c;
int n= blockIdy.y * blockDim.y + threadIdx.y;
int i= blockIdx.x * blockDim.x + threadIdx.x;
if (n>=total || i>=total)
return;
a = values[n];
b = values[i] - a;
c = b*b;
if( c < 10)
newvalues[i] = c;
// I don't know your problem statement but i think it should be like: newvalues[n*total+i] = c;
}
更新:
这是您应该如何调用内核
This is how you should call the kernel
dim3 block(16,16);
dim3 grid ( (total+15)/16, (total+15)/16 );
calc<<<grid,block>>>(float *val, float *newval, int T);
同时请确保在内核中添加此行(参见更新的内核)
Also make sure you add this line in kernel (see updated kernel)
if (n>=total || i>=total)
return;
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