我是opencl编程的新手，并尝试在C中创建以下“hello world”类型的OpenCL程序。
内核代码（hello.cl）
__kernel void hello(__global int* input, __global int* output, const unsigned int count)
{
int i = get_global_id(0);
if(i < count)
output[i] = input[i] * input[i];
}
主机代码：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define DATA_SIZE (10)
#ifdef __APPLE__
#include <OpenCL/opencl.h>
#else
#include <CL/cl.h>
#endif
#define MAX_SOURCE_SIZE (0x100000)
int main()
{
size_t count = DATA_SIZE;
cl_platform_id platform_id = NULL;
cl_device_id device_id = NULL;
cl_context context = NULL;
cl_command_queue command_queue = NULL;
cl_mem memobj = NULL;
cl_program program = NULL;
cl_kernel kernel = NULL;
cl_uint ret_num_devices;
cl_uint ret_num_platforms;
cl_int ret;
size_t global; // local domain size for our calculation
size_t local; // local domain size for our calculation
FILE *fp;
char fileName[] = "./hello.cl";
char *source_str;
size_t source_size;
/* Load the source code containing the kernel*/
fp = fopen(fileName, "r");
if (!fp)
{
fprintf(stderr, "Failed to load kernel.\n");
exit(1);
}
source_str = (char*)malloc(MAX_SOURCE_SIZE);
source_size = fread(source_str, 1, MAX_SOURCE_SIZE, fp);
fclose(fp);
/* Get Platform and Device Info */
ret = clGetPlatformIDs (1, &platform_id, &ret_num_platforms);
ret = clGetDeviceIDs (platform_id, CL_DEVICE_TYPE_DEFAULT, 1, &device_id, &ret_num_devices);
if (ret != CL_SUCCESS)
{
printf("Error: Failed to create a device group!\n");
return EXIT_FAILURE;
}
/* Create OpenCL context */
context = clCreateContext (NULL, 1, &device_id, NULL, NULL, &ret);
if (!context)
{
printf("Error: Failed to create a compute context!\n");
return EXIT_FAILURE;
}
/* Create Command Queue */
command_queue = clCreateCommandQueue (context, device_id, 0, &ret);
if (!command_queue )
{
printf("Error: Failed to create a command commands!\n");
return EXIT_FAILURE;
}
/* Create Kernel Program from the source */
program = clCreateProgramWithSource (context, 1, (const char **)&source_str, (const size_t *)&source_size, &ret);
if (!program)
{
printf("Error: Failed to create compute program!\n");
return EXIT_FAILURE;
}
/* Build Kernel Program */
ret = clBuildProgram(program, 1, &device_id, NULL, NULL, NULL);
if (ret != CL_SUCCESS)
{
size_t len;
char buffer[2048];
printf("Error: Failed to build program executable!\n");
clGetProgramBuildInfo(program, device_id, CL_PROGRAM_BUILD_LOG, sizeof(buffer), buffer, &len);
printf("%s\n", buffer);
exit(1);
}
/* Create OpenCL Kernel */
kernel = clCreateKernel(program, "hello", &ret);
if (!kernel || ret != CL_SUCCESS)
{
printf("Error: Failed to create compute kernel!\n");
exit(1);
}
int data[DATA_SIZE]; // original data set given to device
int results[DATA_SIZE]; // results returned from device
int i = 0;
for(i = 0; i < count; i++)
data[i] = i+1;
cl_mem input; // device memory used for the input array
cl_mem output; // device memory used for the output array
input = clCreateBuffer(context, CL_MEM_READ_ONLY, sizeof(int) * count, NULL, NULL);
output = clCreateBuffer(context, CL_MEM_WRITE_ONLY, sizeof(int) * count, NULL, NULL);
if (!input || !output)
{
printf("Error: Failed to allocate device memory!\n");
exit(1);
}
ret = clEnqueueWriteBuffer(command_queue, input, CL_TRUE, 0, sizeof(int) * count, data, 0, NULL, NULL);
if (ret != CL_SUCCESS)
{
printf("Error: Failed to write to source array!\n");
exit(1);
}
/* Set OpenCL Kernel Parameters */
ret = 0;
ret = clSetKernelArg(kernel, 0, sizeof(cl_mem), &input);
ret |= clSetKernelArg(kernel, 1, sizeof(cl_mem), &output);
ret |= clSetKernelArg(kernel, 2, sizeof(unsigned int), &count);
if (ret != CL_SUCCESS)
{
printf("Error: Failed to set kernel arguments! %d\n", ret);
exit(1);
}
/* Execute OpenCL Kernel */
ret = clGetKernelWorkGroupInfo(kernel, device_id, CL_KERNEL_WORK_GROUP_SIZE, sizeof(local), &local, NULL);
if (ret != CL_SUCCESS)
{
printf("Error: ! %d\n", ret);
scanf("%d",&global);
exit(1);
}
global = (size_t) count;
ret = clEnqueueNDRangeKernel(command_queue, kernel, 1, NULL, &global, &local, 0, NULL, NULL);
clFinish(command_queue);
/* Copy results from the memory buffer */
ret = clEnqueueReadBuffer( command_queue, output, CL_TRUE, 0, sizeof(int) * count, results, 0, NULL, NULL );
if (ret != CL_SUCCESS)
{
printf("Error: Failed to read output array! %d\n", ret);
exit(1);
}
// Validate our results
//
int correct = 0;
for(i = 0; i < count; i++)
{
printf("%d-%d\n",data[i],results[i]);
if(results[i] == data[i] * data[i])
correct++;
}
// Print a brief summary detailing the results
//
printf("Computed '%d/%d' correct values!\n", correct, count);
scanf("%d",&ret);
/* Finalization */
ret = clFlush(command_queue);
ret = clFinish(command_queue);
ret = clReleaseKernel(kernel);
ret = clReleaseProgram(program);
ret = clReleaseMemObject(memobj);
ret = clReleaseCommandQueue(command_queue);
ret = clReleaseContext(context);
clReleaseMemObject(input);
clReleaseMemObject(output);
free(source_str);
return 0;
}
这似乎是非常简单的代码，但是，结果数组包含所有零值。谁能告诉我我在这里犯的错误。该计划的输出如下：
1-0
2-0
3-0
4-0
5-0
6-0
7-0
8-0
9-0
10-0
Computed '0/10' correct values!
我无法找到任何因为gpu没有计算出正确值的原因。
答案 0 :(得分：1)
您没有检查validate_on_submit的返回值，这几乎肯定是失败的，因为您无法确保全局尺寸是本地尺寸的整数倍。
查询clEnqueueNDRangeKernel的结果可能类似于256，但您的全局作业大小为10.您无法将包含10个项目的作业细分为256个组。