设备表示它可用，但无法在 OpenCL 中创建上下文

Device says it is available, but can't create context in OpenCL

本文关键字：OpenCL 上下文 创建 表示      更新时间：2023-10-16

我尝试在英特尔CPU上运行程序。我使用实际的英特尔SDK，它编译并工作到应该创建上下文的地步。这是程序的输出：

=====  Platform 0 =====
PROFILE = FULL_PROFILE
VERSION = OpenCL 1.2 LINUX
NAME = Intel(R) OpenCL
VENDOR = Intel(R) Corporation
VENDOR = cl_khr_fp64 cl_khr_icd cl_khr_global_int32_base_atomics        cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomics cl_khr_byte_addressable_store cl_intel_printf cl_ext_device_fission cl_intel_exec_by_local_thread 
=== 1 OpenCL device(s) found on platform: 0
=== --- Device -- 0 
DEVICE_NAME = Intel(R) Core(TM)2 Duo CPU     P8400  @ 2.26GHz
DEVICE_VENDOR = Intel(R) Corporation
DEVICE_VERSION = OpenCL 1.2 (Build 67279)
DRIVER_VERSION = 1.2
DEVICE_MAX_COMPUTE_UNITS = 2
DEVICE_MAX_CLOCK_FREQUENCY = 2260
DEVICE_GLOBAL_MEM_SIZE = 4035719168
DEVICE_AVAILABLE = Yes
Unable to create GPU or CPU context
CL_DEVICE_NOT_AVAILABLE
unable to create context. Abort.

这就是造成问题的代码。

cl_context CTrainMLP_CreateContext(){
cl_int errNum;
cl_uint numPlatforms;
cl_platform_id firstPlatformId;
cl_context context=NULL;
cl_device_id device;
//get Platform and choose first one
errNum = clGetPlatformIDs(1,&firstPlatformId, &numPlatforms);
if(errNum != CL_SUCCESS || numPlatforms<=0){
cerr<<"No OpenCL platforum found!"<<endl;
return NULL;
}
char buffer[10240];
printf("=====  Platform 0 =====n");
clGetPlatformInfo(firstPlatformId,CL_PLATFORM_PROFILE,10240, buffer,NULL);
printf("  PROFILE = %sn", buffer);
clGetPlatformInfo(firstPlatformId,CL_PLATFORM_VERSION,10240, buffer,NULL);
printf("  VERSION = %sn", buffer);
clGetPlatformInfo(firstPlatformId,CL_PLATFORM_NAME,10240, buffer,NULL);
printf("  NAME = %sn", buffer);
clGetPlatformInfo(firstPlatformId,CL_PLATFORM_VENDOR,10240, buffer,NULL);
printf("  VENDOR = %sn", buffer);
clGetPlatformInfo(firstPlatformId,CL_PLATFORM_EXTENSIONS,10240, buffer,NULL);
printf("  VENDOR = %sn", buffer);
//  clGetPlatformInfo(platforms[i],CL_PLATFORM_EXTENSIONS,10240,buffer,NULL);
//  printf("  EXTENSIONS = %sn", buffer);
cl_uint devices_n;
// get the GPU-devices of platform i, print details of the device
errNum = clGetDeviceIDs( firstPlatformId, CL_DEVICE_TYPE_CPU, 1, &device, 
    &devices_n);
if (errNum != CL_SUCCESS)
  printf("error getting device IDSn");
printf("  === %d OpenCL device(s) found on platform: 0nn", devices_n);
for (unsigned int d=0; d<devices_n; d++)
{
  char buffer[10240];
  cl_uint buf_uint;
  cl_ulong buf_ulong;
  cl_bool buf_bool;
  printf("  === --- Device -- %d n", d);
  (clGetDeviceInfo(device, CL_DEVICE_NAME, sizeof(buffer), 
       buffer, NULL));
  printf("    DEVICE_NAME = %sn", buffer);
  (clGetDeviceInfo(device, CL_DEVICE_VENDOR, sizeof(buffer), 
       buffer, NULL));
  printf("    DEVICE_VENDOR = %sn", buffer);
  (clGetDeviceInfo(device, CL_DEVICE_VERSION, sizeof(buffer), 
       buffer, NULL));
  printf("    DEVICE_VERSION = %sn", buffer);
  (clGetDeviceInfo(device, CL_DRIVER_VERSION, sizeof(buffer), 
       buffer, NULL));
  printf("    DRIVER_VERSION = %sn", buffer);
  (clGetDeviceInfo(device, CL_DEVICE_MAX_COMPUTE_UNITS, 
       sizeof(buf_uint), &buf_uint, NULL));
  printf("    DEVICE_MAX_COMPUTE_UNITS = %un", (unsigned int)buf_uint);
  (clGetDeviceInfo(device, CL_DEVICE_MAX_CLOCK_FREQUENCY, 
       sizeof(buf_uint), &buf_uint, NULL));
  printf("    DEVICE_MAX_CLOCK_FREQUENCY = %un", (unsigned int)buf_uint);
  (clGetDeviceInfo(device, CL_DEVICE_GLOBAL_MEM_SIZE, 
       sizeof(buf_ulong), &buf_ulong, NULL));
  printf("    DEVICE_GLOBAL_MEM_SIZE = %unn", (unsigned int)buf_ulong);
  (clGetDeviceInfo(device, CL_DEVICE_AVAILABLE, 
       sizeof(buf_bool), &buf_bool, NULL));
  printf("    DEVICE_AVAILABLE = %snn", buf_bool?"Yes":"No");
}
if (devices_n == 0)
{
  printf("error, on platform 0, there is no GPU devicen");
}
cl_context_properties contextProperties[3]={
  CL_CONTEXT_PLATFORM,
  (cl_context_properties)firstPlatformId,
  0
};
  context = clCreateContextFromType(contextProperties,       CL_DEVICE_TYPE_ALL,NULL,NULL,&errNum);
 if (errNum!= CL_SUCCESS){
  cerr<<"Unable to create GPU or CPU context"<<endl;
  check_error(errNum);
  return NULL;
 }
cout<<"Created CPU context"<<endl;
return context;
}

为什么OpenCL说，设备是可用的，但当它应该创建上下文时，却以"设备不可用"失败？

因此，一种可能的解释可能是，正如文章中所解释的，这是由于英特尔SDK造成的。引用主要思想：

Intel OpenCL CPU至少需要SSE 4.1。Core 2 Duo只上升至SSSE3。

给出的解决方案是：

安装AMD OpenCL CPU驱动程序。它只需要SSE2。

不使用clCreateContextFromType()，只使用clCreateContext()并将从clGetDeviceIDs()返回的CPU设备的设备id传递给它。

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