我有一个 CUDA 内核，它获取边缘图像并对其进行处理以创建一个较小的边缘像素的一维数组。现在这是奇怪的行为。每次我运行内核并计算“d_nlist”中的边缘像素数（参见 printf 附近的代码）时，我每次都会得到更大的像素数，即使我使用相同的图像并完全停止程序并重新跑。因此，每次我运行它时，运行它需要更长的时间，直到最终，它抛出一个未捕获的异常。
我的问题是，我怎样才能阻止这种情况发生，以便每次运行内核时都能获得一致的结果？
我的设备是 Geforce 620。
常数：
THREADS_X = 32
THREADS_Y = 4
PIXELS_PER_THREAD = 4
MAX_QUEUE_LENGTH = THREADS_X * THREADS_Y * PIXELS_PER_THREAD
IMG_WIDTH = 256
IMG_HEIGHT = 256
IMG_SIZE = IMG_WIDTH * IMG_HEIGHT
BLOCKS_X = IMG_WIDTH / (THREADS_X * PIXELS_PER_THREAD)
BLOCKS_Y = IMG_HEIGHT / THREADS_Y
内核如下：
__global__ void convert2DEdgeImageTo1DArray( unsigned char const * const image,
unsigned int* const list, int* const glob_index ) {
unsigned int const x = blockIdx.x * THREADS_X*PIXELS_PER_THREAD + threadIdx.x;
unsigned int const y = blockIdx.y * THREADS_Y + threadIdx.y;
volatile int qindex = -1;
volatile __shared__ int sh_qindex[THREADS_Y];
volatile __shared__ int sh_qstart[THREADS_Y];
sh_qindex[threadIdx.y] = -1;
// Start by making an array
volatile __shared__ unsigned int sh_queue[MAX_QUEUE_LENGTH];
// Fill the queue
for(int i=0; i<PIXELS_PER_THREAD; i++)
{
int const xx = i*THREADS_X + x;
// Read one image pixel from global memory
unsigned char const pixel = image[y*IMG_WIDTH + xx];
unsigned int const queue_val = (y << 16) + xx;
if(pixel)
{
do {
qindex++;
sh_qindex[threadIdx.y] = qindex;
sh_queue[threadIdx.y*THREADS_X*PIXELS_PER_THREAD + qindex] = queue_val;
} while (sh_queue[threadIdx.y*THREADS_X*PIXELS_PER_THREAD + qindex] != queue_val);
}
// Reload index from smem (last thread to write to smem will have updated it)
qindex = sh_qindex[threadIdx.y];
}
// Let thread 0 reserve the space required in the global list
__syncthreads();
if(threadIdx.x == 0 && threadIdx.y == 0)
{
// Find how many items are stored in each list
int total_index = 0;
#pragma unroll
for(int i=0; i<THREADS_Y; i++)
{
sh_qstart[i] = total_index;
total_index += (sh_qindex[i] + 1u);
}
// Calculate the offset in the global list
unsigned int global_offset = atomicAdd(glob_index, total_index);
#pragma unroll
for(int i=0; i<THREADS_Y; i++)
{
sh_qstart[i] += global_offset;
}
}
__syncthreads();
// Copy local queues to global queue
for(int i=0; i<=qindex; i+=THREADS_X)
{
if(i + threadIdx.x > qindex)
break;
unsigned int qvalue = sh_queue[threadIdx.y*THREADS_X*PIXELS_PER_THREAD + i + threadIdx.x];
list[sh_qstart[threadIdx.y] + i + threadIdx.x] = qvalue;
}
}
以下是调用内核的方法：
void call2DTo1DKernel(unsigned char const * const h_image)
{
// Device side allocation
unsigned char *d_image = NULL;
unsigned int *d_list = NULL;
int h_nlist, *d_nlist = NULL;
cudaMalloc((void**)&d_image, sizeof(unsigned char)*IMG_SIZE);
cudaMalloc((void**)&d_list, sizeof(unsigned int)*IMG_SIZE);
cudaMalloc((void**)&d_nlist, sizeof(int));
// Time measurement initialization
cudaEvent_t start, stop, startio, stopio;
cudaEventCreate(&start);
cudaEventCreate(&stop);
cudaEventCreate(&startio);
cudaEventCreate(&stopio);
// Start timer w/ io
cudaEventRecord(startio,0);
// Copy image data to device
cudaMemcpy((void*)d_image, (void*)h_image, sizeof(unsigned char)*IMG_SIZE, cudaMemcpyHostToDevice);
// Start timer
cudaEventRecord(start,0);
// Kernel call
// Phase 1 : Convert 2D binary image to 1D pixel array
dim3 dimBlock1(THREADS_X, THREADS_Y);
dim3 dimGrid1(BLOCKS_X, BLOCKS_Y);
convert2DEdgeImageTo1DArray<<<dimGrid1, dimBlock1>>>(d_image, d_list, d_nlist);
// Stop timer
cudaEventRecord(stop,0);
cudaEventSynchronize(stop);
// Stop timer w/ io
cudaEventRecord(stopio,0);
cudaEventSynchronize(stopio);
// Time measurement
cudaEventElapsedTime(&et,start,stop);
cudaEventElapsedTime(&etio,startio,stopio);
// Time measurement deinitialization
cudaEventDestroy(start);
cudaEventDestroy(stop);
cudaEventDestroy(startio);
cudaEventDestroy(stopio);
// Get list size
cudaMemcpy((void*)&h_nlist, (void*)d_nlist, sizeof(int), cudaMemcpyDeviceToHost);
// Report on console
printf("%d pixels processed...\n", h_nlist);
// Device side dealloc
cudaFree(d_image);
cudaFree(d_space);
cudaFree(d_list);
cudaFree(d_nlist);
}
非常感谢大家的帮助。