table of contents
| CLSETKERNELARG(3clc) | OpenCL Manual | CLSETKERNELARG(3clc) |
NAME¶
clSetKernelArg - Used to set the argument value for a specific argument of a kernel.
¶
cl_int clSetKernelArg(cl_kernel kernel, cl_uint arg_index, size_t arg_size, const void *arg_value);
PARAMETERS¶
kernel
arg_index
arg_value
If the argument is a memory object (buffer, image or image array), the arg_value entry will be a pointer to the appropriate buffer, image or image array object. The memory object must be created with the context associated with the kernel object. If the argument is a buffer object, the arg_value pointer can be NULL or point to a NULL value in which case a NULL value will be used as the value for the argument declared as a pointer to global(3clc) or constant(3clc) memory in the kernel. If the argument is declared with the local(3clc) qualifier, the arg_value entry must be NULL. If the argument is of type sampler_t, the arg_value entry must be a pointer to the sampler object.
If the argument is declared to be a pointer of a built-in scalar or vector type, or a user defined structure type in the global or constant address space, the memory object specified as argument value must be a buffer object (or NULL). If the argument is declared with the constant(3clc) qualifier, the size in bytes of the memory object cannot exceed CL_DEVICE_MAX_CONSTANT_BUFFER_SIZE and the number of arguments declared as pointers to constant(3clc) memory cannot exceed CL_DEVICE_MAX_CONSTANT_ARGS.
The memory object specified as argument value must be a 2D image object if the argument is declared to be of type image2d_t. The memory object specified as argument value must be a 3D image object if argument is declared to be of type image3d_t. The memory object specified as argument value must be a 1D image object if the argument is declared to be of type image1d_t. The memory object specified as argument value must be a 1D image buffer object if the argument is declared to be of type image1d_buffer_t. The memory object specified as argument value must be a 1D image array object if argument is declared to be of type image1d_array_t. The memory object specified as argument value must be a 2D image array object if argument is declared to be of type image2d_array_t.
For all other kernel arguments, the arg_value entry must be a pointer to the actual data to be used as argument value.
arg_size
NOTES¶
A kernel object does not update the reference count for objects such as memory, sampler objects specified as argument values by clSetKernelArg. Users may not rely on a kernel object to retain objects specified as argument values to the kernel.
Implementations shall not allow cl_kernel objects to hold reference counts to cl_kernel arguments, because no mechanism is provided for the user to tell the kernel to release that ownership right. If the kernel holds ownership rights on kernel args, that would make it impossible for the user to tell with certainty when he may safely release user allocated resources associated with OpenCL objects such as the cl_mem backing store used with CL_MEM_USE_HOST_PTR.
An OpenCL API call is considered to be thread-safe if the internal state as managed by OpenCL remains consistent when called simultaneously by multiple host threads. OpenCL API calls that are thread-safe allow an application to call these functions in multiple host threads without having to implement mutual exclusion across these host threads i.e. they are also re-entrant-safe.
All OpenCL API calls are thread-safe except clSetKernelArg. clSetKernelArg is safe to call from any host thread, and is safe to call re-entrantly so long as concurrent calls operate on different cl_kernel objects. However, the behavior of the cl_kernel object is undefined if clSetKernelArg is called from multiple host threads on the same cl_kernel object at the same time. Please note that there are additional limitations as to which OpenCL APIs may be called from OpenCL callback functions -- please see section 5.9.
There is an inherent race condition in the design of OpenCL that occurs between setting a kernel argument and using the kernel with clEnqueueNDRangeKernel(3clc) or clEnqueueTask(3clc). Another host thread might change the kernel arguments between when a host thread sets the kernel arguments and then enqueues the kernel, causing the wrong kernel arguments to be enqueued. Rather than attempt to share cl_kernel objects among multiple host threads, applications are strongly encouraged to make additional cl_kernel objects for kernel functions for each host thread.
ERRORS¶
clSetKernelArg returns CL_SUCCESS if the function is executed successfully. Otherwise, it returns one of the following errors:
Example¶
| kernel void image_filter (int n, int m, __constant float *filter_weights, __read_only image2d_t src_image, __write_only image2d_t dst_image) { ... } |
Argument index values for image_filter will be 0 for n, 1 for m, 2 for filter_weights, 3 for src_image and 4 for dst_image.
SPECIFICATION¶
OpenCL Specification[1]
SEE ALSO¶
clCreateKernel(3clc), clCreateKernelsInProgram(3clc), clReleaseKernel(3clc), clRetainKernel(3clc), clGetKernelInfo(3clc), clGetKernelWorkGroupInfo(3clc)
AUTHORS¶
The Khronos Group
COPYRIGHT¶
Copyright © 2007-2011 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and/or associated documentation files (the
"Materials"), to deal in the Materials without restriction,
including without limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of the Materials, and to
permit persons to whom the Materials are furnished to do so, subject to the
condition that this copyright notice and permission notice shall be included
in all copies or substantial portions of the Materials.
NOTES¶
- 1.
- OpenCL Specification
| 01/14/2021 | The Khronos Group |