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
           A valid kernel object.

       arg_index
           The argument index. Arguments to the kernel are referred by indices that go from 0 for
           the leftmost argument to n - 1, where n is the total number of arguments declared by a
           kernel.

       arg_value
           A pointer to data that should be used as the argument value for argument specified by
           arg_index. The argument data pointed to by arg_value is copied and the arg_value
           pointer can therefore be reused by the application after clSetKernelArg returns. The
           argument value specified is the value used by all API calls that enqueue kernel
           (clEnqueueNDRangeKernel(3clc) and clEnqueueTask(3clc)) until the argument value is
           changed by a call to clSetKernelArg for kernel.

           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
           Specifies the size of the argument value. If the argument is a memory object, the size
           is the size of the buffer or image object type. For arguments declared with the
           local(3clc) qualifier, the size specified will be the size in bytes of the buffer that
           must be allocated for the local(3clc) argument. If the argument is of type sampler_t,
           the arg_size value must be equal to sizeof(cl_sampler). For all other arguments, the
           size will be the size of argument type.

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:

       ·   CL_INVALID_KERNEL if kernel is not a valid kernel object.

       ·   CL_INVALID_ARG_INDEX if arg_index is not a valid argument index.

       ·   CL_INVALID_ARG_VALUE if arg_value specified is not a valid value.

       ·   CL_INVALID_MEM_OBJECT for an argument declared to be a memory object when the
           specified arg_value is not a valid memory object.

       ·   CL_INVALID_SAMPLER for an argument declared to be of type sampler_t when the specified
           arg_value is not a valid sampler object.

       ·   CL_INVALID_ARG_SIZE if arg_size does not match the size of the data type for an
           argument that is not a memory object or if the argument is a memory object and
           arg_size != sizeof(cl_mem) or if arg_size is zero and the argument is declared with
           the local(3clc) qualifier or if the argument is a sampler and arg_size !=
           sizeof(cl_sampler).

       ·   CL_INVALID_ARG_VALUE if the argument is an image declared with the read_only qualifier
           and arg_value refers to an image object created with cl_mem_flags of CL_MEM_WRITE or
           if the image argument is declared with the write_only qualifier and arg_value refers
           to an image object created with cl_mem_flags of CL_MEM_READ.

       ·   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.

   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
           page 160, section 5.7.2 - Setting Kernel Arguments