【发布时间】：2014-01-24 23:48:33
【问题描述】：
因此，我正试图让某些代码在 OpenCL 中工作。
由于我没有得到最初预期的结果，我一直在尝试各种方法来找出问题所在。所以我想出了下面附加的代码，成功执行后它没有产生预期的结果。
这段代码的最初设想是执行指定数量的线程并将线程号复制到一个数组中。
Threads: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
但是我得到的结果。
Threads: 0 0 0 3 0 0 0 7 0 0 0 11 0 0 0 15
我得到的结果是一种模式。所以每一个
(n % 4)
它似乎在我的数组中放了一个数字。我开始考虑是否由于某种原因代码被视为int 并转换为char。
gcc main.c -o threadsopencl -std=c99 -framework OpenCL
#ifdef __APPLE__
#include <OpenCL/opencl.h>
#else
#include <CL/cl.h>
#endif
#include <stdlib.h> // warning: implicit declaration of function ‘malloc’
#include <stdio.h> // error: ‘stderr’ undeclared (first use in this function)
int main(int argc, char **argv)
{
/* Retrieve Platforms */
cl_uint Platforms = 0;
printf("Checking for OpenCL platforms.\n");
if (CL_SUCCESS == clGetPlatformIDs ( 0, NULL, &Platforms))
{
printf("Found %d platform.\n", Platforms);
if (Platforms > 0)
{
/* Retrieve Platform ID */
printf("Retrieving OpenCL platform details.\n");
cl_platform_id *Platform = malloc((sizeof(cl_platform_id) * Platforms));
clGetPlatformIDs( Platforms, Platform, &Platforms);
/* Retrieve Devices on Platform */
cl_uint GPUs = 0;
printf("Retrieving GPU devices associated with the detected platform.\n");
clGetDeviceIDs( Platform[0], CL_DEVICE_TYPE_GPU, 0, NULL, &GPUs);
if (GPUs > 0)
{
printf("Found %d GPU device(s).\n", GPUs);
cl_device_id *GPU = malloc((sizeof(cl_device_id) * GPUs));
clGetDeviceIDs( Platform[0], CL_DEVICE_TYPE_GPU, GPUs, GPU, &GPUs);
cl_uint Error;
printf("Creating OpenCL context and associating it with the detected GPU device.\n");
//clCreateContext(NULL, 1, &devices[device_no], &pfn_notify, NULL, &_err)
cl_context GPUcontext = clCreateContext(NULL, 1, &GPU[0], 0, NULL, &Error);
//clCreateContextFromType( NULL, CL_DEVICE_TYPE_GPU, NULL, NULL, &Error);
if (Error != CL_SUCCESS)
{
printf("Failed to create an OpenCL context!\n");
return 1;
}
const char *program_source[] = {
"__kernel void NumberOfThreads( __global uchar *thread)\n",
"{\n",
"uchar id = convert_uchar(get_global_id(0));\n",
"thread[id] = id;\n",
"}\n"
};
printf("Creating a program for execution on the device.\n");
cl_program AES = clCreateProgramWithSource( GPUcontext, sizeof(program_source)/sizeof(*program_source), program_source, NULL, &Error);
if (Error != CL_SUCCESS)
{
printf("Failed to create a program from source!\n");
return 1;
}
printf("Attempting compilation!\n");
if (clBuildProgram( AES, GPUs, &GPU[0], "", NULL, NULL) != CL_SUCCESS) {
printf("Program compilation failed!\n");
char buffer[10240];
clGetProgramBuildInfo( AES, GPU[0], CL_PROGRAM_BUILD_LOG, sizeof(buffer), buffer, NULL);
fprintf(stderr, "CL Compilation failed:\n%s", buffer);
exit(2); // abort();
}
/* Since OpenCL compilation failed is due to incomplete code work */
printf("Allocating space for the data to be executed within the context.\n");
cl_mem Threads = clCreateBuffer( GPUcontext, CL_MEM_WRITE_ONLY, 16*sizeof(char), NULL, &Error);
if (Error != CL_SUCCESS)
{
printf("Failed to allocate buffer for State Matrix!\n");
return 1;
}
printf("Creating an OpenCL kernel!\n");
cl_kernel ThreadsKernel = clCreateKernel( AES, "NumberOfThreads", &Error);
clSetKernelArg( ThreadsKernel, 0, sizeof(cl_mem), &Threads);
if (Error != CL_SUCCESS)
{
printf("Failed to create kernel object!\n");
return 1;
}
printf("Setting up an execution queue.\n");
cl_command_queue ExecutionQueue = clCreateCommandQueue( GPUcontext, GPU[0], 0, &Error);
if (Error != CL_SUCCESS)
{
printf("Failed to create command queue!\n");
return 1;
}
printf("Commencing with kernel execution!\n");
cl_event ExecutionComplete;
size_t global_work_size[1] = { 16 };
if (clEnqueueNDRangeKernel( ExecutionQueue, ThreadsKernel, 1, NULL, global_work_size, NULL, 0, NULL, &ExecutionComplete) != CL_SUCCESS)
{
//printf("Failed to execute kernel! Error %d\n", (unsigned int)Error);
switch(Error)
{
case CL_INVALID_PROGRAM_EXECUTABLE:
printf("CL_INVALID_PROGRAM_EXECUTABLE\n");
break;
case CL_INVALID_COMMAND_QUEUE:
printf("CL_INVALID_COMMAND_QUEUE\n");
break;
case CL_INVALID_KERNEL:
printf("CL_INVALID_KERNEL\n");
break;
case CL_INVALID_CONTEXT:
printf("CL_INVALID_CONTEXT\n");
break;
case CL_INVALID_KERNEL_ARGS:
printf("CL_INVALID_KERNEL_ARGS\n");
break;
case CL_INVALID_WORK_DIMENSION:
printf("CL_INVALID_WORK_DIMENSION\n");
break;
case CL_INVALID_GLOBAL_WORK_SIZE:
printf("CL_INVALID_GLOBAL_WORK_SIZE\n");
break;
case CL_INVALID_WORK_GROUP_SIZE:
printf("CL_INVALID_WORK_GROUP_SIZE\n");
break;
case CL_INVALID_WORK_ITEM_SIZE:
printf("CL_INVALID_WORK_ITEM_SIZE\n");
break;
case CL_INVALID_GLOBAL_OFFSET:
printf("CL_INVALID_GLOBAL_OFFSET\n");
break;
case CL_OUT_OF_RESOURCES:
printf("CL_OUT_OF_RESOURCES\n");
break;
case CL_MEM_OBJECT_ALLOCATION_FAILURE:
printf("CL_MEM_OBJECT_ALLOCATION_FAILURE\n");
break;
case CL_INVALID_EVENT_WAIT_LIST:
printf("CL_INVALID_EVENT_WAIT_LIST\n");
break;
case CL_OUT_OF_HOST_MEMORY:
printf("CL_OUT_OF_HOST_MEMORY\n");
break;
default:
printf("Failed to execute kernel! %u\n", (unsigned int)Error);
}
return 1;
}
clWaitForEvents( 1, &ExecutionComplete);
clReleaseEvent( ExecutionComplete);
printf("ThreadValue:");
for ( char Loop = 0; Loop < 16; Loop++)
{
unsigned char ThreadValue = 0;
if (clEnqueueReadBuffer( ExecutionQueue, Threads, CL_TRUE, Loop, 1, &ThreadValue, 0, NULL, NULL) != CL_SUCCESS)
{
printf("Failed to copy data back from Device to Host!\n");
return 1;
}
printf(" %d", ThreadValue);
}
printf("\n");
printf("Freeing memory and exiting!\n");
clReleaseMemObject(Threads);
clReleaseKernel(ThreadsKernel);
clReleaseProgram(AES);
clReleaseContext(GPUcontext);
}
}
}
return 0;
}
【问题讨论】：
-
看来你在内核内部做 tid * tid，所以预期的结果应该是 0,1,3,9 ...在我的 AMD 机器上，我得到了这个结果。
-
get_global_id(0) -> 检索线程号，然后将其转换为无符号字符，然后在线程数组中选择它（最初在内核调用期间传递参数），然后存储线程号*乘以自身。
-
修复了（id * id）。但即使我运行代码，它也会打印 0 0 0 9 0 0 0 49 0 0 0 121 0 0 0 225。所以 3 个字节的 NULL 值，然后是内核函数的乘法运算。代码应该显示以下结果：0 1 4 9 16 25 36 49 64 91 100 121 144 169 196 225
标签： mac osx c opencl gpu gpgpu amd-processor