clGetKernelWorkGroupInfo

Returns information about the kernel object that may be specific to a device.

cl_int clGetKernelWorkGroupInfo ( cl_kernel  kernel ,
  cl_device_id  device ,
  cl_kernel_work_group_info  param_name ,
  size_t  param_value_size ,
  void  *param_value ,
  size_t  *param_value_size_ret )

Parameters

kernel

Specifies the kernel object being queried.

device

Identifies a specific device in the list of devices associated with kernel. The list of devices is the list of devices in the OpenCL context that is associated with kernel. If the list of devices associated with kernel is a single device, device can be a NULL value.

param_name

Specifies the information to query. The list of supported param_name types and the information returned in param_value by clGetKernelWorkGroupInfo is described in the table below.

param_value

A pointer to memory where the appropriate result being queried is returned. If param_value is NULL, it is ignored.

param_value_size

Used to specify the size in bytes of memory pointed to by param_value. This size must be ≥ size of return type as described in the table below.

cl_kernel_work_group_info Return Type Info. returned in param_value
CL_KERNEL_GLOBAL_WORK_SIZE size_t[3] This provides a mechanism for the application to query the maximum global size that can be used to execute a kernel (i.e. global_work_size argument to clEnqueueNDRangeKernel) on a custom device given by device or a built-in kernel on an OpenCL device given by device.

If device is not a custom device or kernel is not a built-in kernel, clGetKernelArgInfo returns the error CL_INVALID_VALUE.

CL_KERNEL_WORK_GROUP_SIZE size_t This provides a mechanism for the application to query the maximum work-group size that can be used to execute a kernel on a specific device given by device. The OpenCL implementation uses the resource requirements of the kernel (register usage etc.) to determine what this work-group size should be.
CL_KERNEL_COMPILE_- WORK_GROUP_SIZE size_t[3] Returns the work-group size specified by the __attribute__((reqd_work_group_size(X, Y, Z))) qualifier. See Function Qualifiers. If the work-group size is not specified using the above attribute qualifier (0, 0, 0) is returned.
CL_KERNEL_LOCAL_MEM_SIZE cl_ulong

Returns the amount of local memory in bytes being used by a kernel. This includes local memory that may be needed by an implementation to execute the kernel, variables declared inside the kernel with the __local address qualifier and local memory to be allocated for arguments to the kernel declared as pointers with the __local address qualifier and whose size is specified with clSetKernelArg.

If the local memory size, for any pointer argument to the kernel declared with the __local address qualifier, is not specified, its size is assumed to be 0.

CL_KERNEL_PREFERRED_WORK_- GROUP_SIZE_MULTIPLE size_t Returns the preferred multiple of workgroup size for launch. This is a performance hint. Specifying a workgroup size that is not a multiple of the value returned by this query as the value of the local work size argument to clEnqueueNDRangeKernel will not fail to enqueue the kernel for execution unless the work-group size specified is larger than the device maximum.
CL_KERNEL_PRIVATE_MEM_SIZE cl_ulong Returns the minimum amount of private memory, in bytes, used by each workitem in the kernel. This value may include any private memory needed by an implementation to execute the kernel, including that used by the language built-ins and variable declared inside the kernel with the __private qualifier.
param_value_size_ret

Returns the actual size in bytes of data copied to param_value. If param_value_size_ret is NULL, it is ignored.

Errors

Returns CL_SUCCESS if the function is executed successfully. Otherwise, it returns one of the following errors:

  • CL_INVALID_DEVICE if device is not in the list of devices associated with kernel or if device is NULL but there is more than one device associated with kernel.
  • CL_INVALID_VALUE if param_name is not valid, or if size in bytes specified by param_value_size is < size of return type as described in the table above and param_value is not NULL.
  • CL_INVALID_VALUE if param_name is CL_KERNEL_GLOBAL_WORK_SIZE and device is not a custom device or kernel is not a built-in kernel.
  • CL_INVALID_KERNEL if kernel is a not a valid kernel object.
  • CL_OUT_OF_RESOURCES if there is a failure to allocate resources required by the OpenCL implementation on the device.
  • CL_OUT_OF_HOST_MEMORY if there is a failure to allocate resources required by the OpenCL implementation on the host.

Specification

OpenCL Specification

Also see

clCreateKernel, clCreateKernelsInProgram, clReleaseKernel, clRetainKernel, clSetKernelArg, clGetKernelInfo

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