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<refentry>
<refentryinfo>
<keywordset>
<keyword>clSetKernelArg</keyword>
</keywordset>
</refentryinfo>
<refmeta>
<refentrytitle>
clSetKernelArg
</refentrytitle>
<refmiscinfo>
<copyright>
<year>2007-2010</year>
<holder>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.</holder>
</copyright>
</refmiscinfo>
<manvolnum>3</manvolnum>
</refmeta>
<!-- ================================ SYNOPSIS -->
<refnamediv id="clSetKernelArg">
<refname>
clSetKernelArg
</refname>
<refpurpose>
Used to set the argument value for a specific argument of a kernel.
</refpurpose>
</refnamediv>
<refsynopsisdiv xmlns:xlink="http://www.w3.org/1999/xlink"><title></title>
<funcsynopsis>
<funcprototype>
<funcdef>
<link xlink:href="scalarDataTypes.html">cl_int</link>
<function>clSetKernelArg</function>
</funcdef>
<paramdef><link xlink:href="abstractDataTypes.html">cl_kernel</link><parameter>kernel</parameter></paramdef>
<paramdef><link xlink:href="scalarDataTypes.html">cl_uint</link><parameter>arg_index</parameter></paramdef>
<paramdef><link xlink:href="scalarDataTypes.html">size_t</link><parameter>arg_size</parameter></paramdef>
<paramdef>const <link xlink:href="scalarDataTypes.html">void</link><parameter>*arg_value</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- ================================ PARAMETERS -->
<!-- For each <varlistentry />, place the parameter name in <term /><varname />, then the definition in
<listitem /><para />. When refering to anything
that has a page in this system, use <citerefentry /><refentrytitle /> to make it a link.
-->
<refsect1 id="parameters">
<title>Parameters</title>
<variablelist>
<varlistentry>
<term>
<varname>kernel</varname>
</term>
<listitem>
<para>
A valid kernel object.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>arg_index</varname>
</term>
<listitem>
<para>
The argument index. Arguments to the kernel are referred by indices that go from 0 for the leftmost argument to <emphasis>n</emphasis> - 1, where <emphasis>n</emphasis> is the total number of arguments declared by a kernel.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>arg_value</varname>
</term>
<listitem>
<para>
A pointer to data that should be used as the argument value for argument specified
by <varname>arg_index</varname>. The argument data pointed to by <varname>arg_value</varname> is copied and the <varname>arg_value</varname> pointer can therefore be reused by the application after <function>clSetKernelArg</function> returns. The argument value specified is the value used by all API calls that enqueue <varname>kernel</varname> (<citerefentry><refentrytitle>clEnqueueNDRangeKernel</refentrytitle></citerefentry> and
<citerefentry><refentrytitle>clEnqueueTask</refentrytitle></citerefentry>) until the argument value is changed by a call to <function>clSetKernelArg</function> for <varname>kernel</varname>.
</para>
<para>
If the argument is a memory object (buffer or image), the <varname>arg_value</varname> entry will be a
pointer to the appropriate buffer or image object. The memory object must be created with the context
associated with the kernel object. A NULL value can also be specified if the argument is a buffer
object in which case a NULL value will be used as the value for the argument declared as a
pointer to <varname>__global</varname> or <varname>__constant</varname> memory in the kernel. If the
argument is declared with the <varname>__local</varname> qualifier, the <varname>arg_value</varname>
entry must be NULL. If the argument is of type <varname>sampler_t</varname>, the <varname>arg_value</varname>
entry must be a pointer to the sampler object.
</para>
<para>
If the argument is declared to be a pointer of a built-in or user defined type with
the <varname>__global</varname> or <varname>__constant</varname> qualifier, the memory object specified as
argument value must be a buffer object (or NULL). If the argument is declared with the <varname>__constant</varname>
qualifier, the size in bytes of the memory object cannot exceed CL_DEVICE_MAX_CONSTANT_BUFFER_SIZE and the
number of arguments declared with the <varname>__constant</varname> qualifier cannot exceed
CL_DEVICE_MAX_CONSTANT_ARGS.
</para>
<para>
The memory object specified as argument value must be a 2D image object if the argument is
declared to be of type <varname>image2d_t</varname>. The memory object specified as argument value must
be a 3D image object if argument is declared to be of type <varname>image3d_t</varname>.
</para>
<para>
For all other kernel arguments, the <varname>arg_value</varname> entry must be a pointer to the actual
data to be used as argument value.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<varname>
arg_size
</varname>
</term>
<listitem>
<para>
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 <varname>__local</varname>
qualifier, the size specified will be the size in bytes of the buffer that must be allocated
for the <varname>__local</varname> argument. If the argument is of type <varname>sampler_t</varname>,
the <varname>arg_size</varname> value must be equal to <code>sizeof(cl_sampler)</code>. For all other
arguments, the size will be the size of argument type.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<!-- ================================ NOTES -->
<!-- Use <function /> to refer ONLY to the function that this page describes. All other functions should use
<citerefentry /><refentrytitle /> to make it a link. Use <varname /> for parameters. Use <constant /> for
constants (or anything to be set in monospace, non-bold type. -->
<refsect1 id="notes"><title>Notes</title>
<para>
A kernel object does not update the reference count for objects such as memory, sampler
objects specified as argument values by <function>clSetKernelArg</function>. Users may not rely on a kernel object
to retain objects specified as argument values to the kernel.
</para>
<para>
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
<constant>CL_MEM_USE_HOST_PTR</constant>.
</para>
<para>
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.
</para>
<para>
All OpenCL API calls are thread-safe except <function>clSetKernelArg</function>, which 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
<function>clSetKernelArg</function> is called from multiple host threads on the same cl_kernel object at the same
time.
</para>
<para>
There is an inherent race condition in the design of OpenCL that occurs between setting a kernel argument and
using the kernel with <citerefentry><refentrytitle>clEnqueueNDRangeKernel</refentrytitle></citerefentry> or <citerefentry><refentrytitle>clEnqueueTask</refentrytitle></citerefentry>. 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.
</para>
</refsect1>
<!-- ================================ ERRORS -->
<refsect1 id="errors"><title>Errors</title>
<para>
<function>clSetKernelArg</function> returns <errorname>CL_SUCCESS</errorname> if the function is
executed successfully. Otherwise, it returns one of the following errors:
</para>
<itemizedlist mark="disc">
<listitem>
<errorname>CL_INVALID_KERNEL</errorname> if <varname>kernel</varname> is not a valid kernel object.
</listitem>
<listitem>
<errorname>CL_INVALID_ARG_INDEX</errorname> if <varname>arg_index</varname> is not a valid argument index.
</listitem>
<listitem>
<errorname>CL_INVALID_ARG_VALUE</errorname> if <varname>arg_value</varname> specified is NULL for an argument that is not
declared with the <varname>__local</varname> qualifier or vice-versa.
</listitem>
<listitem>
<errorname>CL_INVALID_MEM_OBJECT</errorname> for an argument declared to be a memory object when the
specified <varname>arg_value</varname> is not a valid memory object.
</listitem>
<listitem>
<errorname>CL_INVALID_SAMPLER</errorname> for an argument declared to be of type <varname>sampler_t</varname> when
the specified <varname>arg_value</varname> is not a valid sampler object.
</listitem>
<listitem>
<errorname>CL_INVALID_ARG_SIZE</errorname> if <varname>arg_size</varname> 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 <varname>arg_size</varname> != <constant>sizeof(cl_mem)</constant> or if <varname>arg_size</varname> is zero
and the argument is declared with the <citerefentry href="local"><refentrytitle>__local</refentrytitle></citerefentry>
qualifier or if the argument is a sampler and <varname>arg_size</varname> != <constant>sizeof(cl_sampler)</constant>.
</listitem>
<listitem>
<errorname>CL_OUT_OF_RESOURCES</errorname> if there is a failure to allocate resources required by the
OpenCL implementation on the device.
</listitem>
<listitem>
<errorname>CL_OUT_OF_HOST_MEMORY</errorname> if there is a failure to allocate resources required by the
OpenCL implementation on the host.
</listitem>
</itemizedlist>
</refsect1>
<!-- ================================ EXAMPLE -->
<!-- DO NOT DELETE IN CASE AN EXAMPLE IS ADDED IN THE FUTURE -->
<!-- -->
<refsect2 id="example1">
<title>
Example
</title>
<informaltable frame="none">
<tgroup cols="1" align="left" colsep="0" rowsep="0">
<colspec colname="col1" colnum="1" />
<tbody>
<row>
<entry>
__kernel void
image_filter (int n, int m,
__constant float *filter_weights,
__read_only image2d_t src_image,
__write_only image2d_t dst_image)
{
...
}
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
<para>
Argument index values for <constant>image_filter</constant> will be 0 for n, 1 for m, 2 for
<constant>filter_weights</constant>, 3 for <constant>src_image</constant> and 4 for <constant>dst_image</constant>.
</para>
</refsect2>
<!-- ================================ SPECIFICATION -->
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<refsect1 id="specification"><title>Specification</title>
<para>
<imageobject>
<imagedata fileref="pdficon_small1.gif" format="gif" />
</imageobject>
<olink uri="clSetKernelArg">OpenCL Specification</olink>
</para>
</refsect1>
<!-- ================================ ALSO SEE -->
<refsect1 id="seealso"><title>Also see</title>
<para>
<citerefentry><refentrytitle>clCreateKernel</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>clCreateKernelsInProgram</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>clReleaseKernel</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>clRetainKernel</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>clGetKernelInfo</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>clGetKernelWorkGroupInfo</refentrytitle></citerefentry>
</para>
</refsect1>
<!-- ================================ COPYRIGHT -->
<!-- Content included from copyright.inc.xsl -->
<refsect3 id="Copyright"><title></title>
<imageobject>
<imagedata fileref="KhronosLogo.jpg" format="jpg" />
</imageobject>
<para />
</refsect3>
</refentry>