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    <title>clSetKernelArg</title>
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    <div class="refentry">
      <a id="id-1"></a>
      <div class="titlepage"></div>
      <div xmlns="" class="refnamediv">
        <a xmlns="http://www.w3.org/1999/xhtml" id="clSetKernelArg"></a>
        <h1>     
            clSetKernelArg
        </h1>
        <p>          
            Used to set the argument value for a specific argument of a kernel.
        </p>
      </div>
      <div class="refsynopsisdiv">
        <h2></h2>
        <div class="funcsynopsis">
          <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
            <tr valign="bottom">
              <td>
                <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef">
                    <a class="link" href="scalarDataTypes.html" target="_top">cl_int</a>
 <strong class="fsfunc">clSetKernelArg</strong>
                (</code>
                <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="_top">cl_kernel</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">kernel</var>, </td>
              </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">cl_uint</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">arg_index</var>, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">size_t</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">arg_size</var>, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td>const <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">void</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*arg_value</var><code>)</code></td>
            </tr>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="parameters"></a>
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">
                    <code class="varname">kernel</code>
                </span>
            </dt>
            <dd>
              <p>
                        A valid kernel object.
                    </p>
            </dd>
            <dt>
              <span class="term">
                    <code class="varname">arg_index</code>
                </span>
            </dt>
            <dd>
              <p>
                        The argument index. Arguments to the kernel are referred by indices that go from 0 for the leftmost argument to <span class="emphasis"><em>n</em></span> - 1, where <span class="emphasis"><em>n</em></span> is the total number of arguments declared by a kernel.
                    </p>
            </dd>
            <dt>
              <span class="term">
                    <code class="varname">arg_value</code>
                </span>
            </dt>
            <dd>
              <p>
                    A pointer to data that should be used as the argument value for argument specified
                        by <code class="varname">arg_index</code>. The argument data pointed to by <code class="varname">arg_value</code> is copied and the <code class="varname">arg_value</code> pointer can therefore be reused by the application after <code class="function">clSetKernelArg</code> returns. The argument value specified is the value used by all API calls that enqueue <code class="varname">kernel</code> (<a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a> and
                        <a class="citerefentry" href="clEnqueueTask.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueTask</span></span></a>) until the argument value is changed by a call to <code class="function">clSetKernelArg</code> for <code class="varname">kernel</code>.
                    </p>
              <p>
                        If the argument is a memory object (buffer or image), the <code class="varname">arg_value</code> 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 <code class="varname">__global</code> or <code class="varname">__constant</code> memory in the kernel. If the 
                        argument is declared with the <code class="varname">__local</code> qualifier, the <code class="varname">arg_value</code> 
                        entry must be NULL. If the argument is of type <code class="varname">sampler_t</code>, the <code class="varname">arg_value</code> 
                        entry must be a pointer to the sampler object. 
                    </p>
              <p>
                        If the argument is declared to be a pointer of a built-in or user defined type with 
                        the <code class="varname">__global</code> or <code class="varname">__constant</code> qualifier, the memory object specified as 
                        argument value must be a buffer object (or NULL). If the argument is declared with the <code class="varname">__constant</code>
                        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 <code class="varname">__constant</code> qualifier cannot exceed
                        CL_DEVICE_MAX_CONSTANT_ARGS.
                    </p>
              <p>
                        The memory object specified as argument value must be a 2D image object if the argument is
                        declared to be of type <code class="varname">image2d_t</code>. The memory object specified as argument value must 
                        be a 3D image object if argument is declared to be of type <code class="varname">image3d_t</code>.
                    </p>
              <p>
                        For all other kernel arguments, the <code class="varname">arg_value</code> entry must be a pointer to the actual 
                        data to be used as argument value.
                    </p>
            </dd>
            <dt>
              <span class="term">
                    <code class="varname"> 
                       arg_size
                    </code>
                </span>
            </dt>
            <dd>
              <p>
                        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 <code class="varname">__local</code> 
                        qualifier, the size specified will be the size in bytes of the buffer that must be allocated 
                        for the <code class="varname">__local</code> argument. If the argument is of type <code class="varname">sampler_t</code>, 
                        the <code class="varname">arg_size</code> value must be equal to <code class="code">sizeof(cl_sampler)</code>. For all other 
                        arguments, the size will be the size of argument type.
                    </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1">
        <a id="notes"></a>
        <h2>Notes</h2>
        <p>
            A kernel object does not update the reference count for objects such as memory, sampler
            objects specified as argument values by <code class="function">clSetKernelArg</code>. Users may not rely on a kernel object
            to retain objects specified as argument values to the kernel.
        </p>
        <p>
            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
            <code class="constant">CL_MEM_USE_HOST_PTR</code>.
        </p>
        <p>
            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.
        </p>
        <p>
All OpenCL API calls are thread-safe except <code class="function">clSetKernelArg</code>, 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
<code class="function">clSetKernelArg</code> is called from multiple host threads on the same cl_kernel object at the same
time. 
        </p>
        <p>
There is an inherent race condition in the design of OpenCL that occurs between setting a kernel argument and
using the kernel with <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a> or <a class="citerefentry" href="clEnqueueTask.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueTask</span></span></a>. 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.
        </p>
      </div>
      <div class="refsect1">
        <a id="errors"></a>
        <h2>Errors</h2>
        <p>
            <code class="function">clSetKernelArg</code> returns <span class="errorname">CL_SUCCESS</span> if the function is
            executed successfully. Otherwise, it returns one of the following errors:
        </p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_KERNEL</span> if <code class="varname">kernel</code> is not a valid kernel object.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_ARG_INDEX</span> if <code class="varname">arg_index</code> is not a valid argument index.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_ARG_VALUE</span> if <code class="varname">arg_value</code> specified is NULL for an argument that is not
                declared with the <code class="varname">__local</code> qualifier or vice-versa.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_MEM_OBJECT</span> for an argument declared to be a memory object when the
                specified <code class="varname">arg_value</code> is not a valid memory object.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_SAMPLER</span> for an argument declared to be of type <code class="varname">sampler_t</code> when 
                the specified <code class="varname">arg_value</code> is not a valid sampler object.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_ARG_SIZE</span> if <code class="varname">arg_size</code> 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 <code class="varname">arg_size</code> != <code class="constant">sizeof(cl_mem)</code> or if <code class="varname">arg_size</code> is zero 
                and the argument is declared with the <a class="citerefentry" href="local.html"><span class="citerefentry"><span class="refentrytitle">__local</span></span></a>
                qualifier or if the argument is a sampler and <code class="varname">arg_size</code> != <code class="constant">sizeof(cl_sampler)</code>.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_OUT_OF_RESOURCES</span> if there is a failure to allocate resources required by the 
                OpenCL implementation on the device.
            </li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_OUT_OF_HOST_MEMORY</span> if there is a failure to allocate resources required by the
                OpenCL implementation on the host.  
            </li>
          </ul>
        </div>
      </div>
      <div class="refsect2">
        <a id="example1"></a>
        <h3>
            Example
        </h3>
        <div class="informaltable">
          <table border="0">
            <colgroup>
              <col align="left" class="col1" />
            </colgroup>
            <tbody>
              <tr>
                <td align="left">
__kernel void
image_filter (int n, int m,
          __constant float *filter_weights,
          __read_only image2d_t src_image,
          __write_only image2d_t dst_image)
{
     ...
}
                        </td>
              </tr>
            </tbody>
          </table>
        </div>
        <p>
            Argument index values for <code class="constant">image_filter</code> will be 0 for n, 1 for m, 2 for
            <code class="constant">filter_weights</code>, 3 for <code class="constant">src_image</code> and 4 for <code class="constant">dst_image</code>.
        </p>
      </div>
      <div class="refsect1">
        <a id="specification"></a>
        <h2>Specification</h2>
        <p>
            <img src="pdficon_small1.gif" />
            
                      
            <a href="http://www.khronos.org/registry/cl/specs/opencl-1.1.pdf#page=125" target="OpenCL Spec">OpenCL Specification</a>
        </p>
      </div>
      <div class="refsect1">
        <a id="seealso"></a>
        <h2>Also see</h2>
        <p>
            <a class="citerefentry" href="clCreateKernel.html"><span class="citerefentry"><span class="refentrytitle">clCreateKernel</span></span></a>, 
            <a class="citerefentry" href="clCreateKernelsInProgram.html"><span class="citerefentry"><span class="refentrytitle">clCreateKernelsInProgram</span></span></a>, 
            <a class="citerefentry" href="clReleaseKernel.html"><span class="citerefentry"><span class="refentrytitle">clReleaseKernel</span></span></a>, 
            <a class="citerefentry" href="clRetainKernel.html"><span class="citerefentry"><span class="refentrytitle">clRetainKernel</span></span></a>, 
            <a class="citerefentry" href="clGetKernelInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetKernelInfo</span></span></a>, 
            <a class="citerefentry" href="clGetKernelWorkGroupInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetKernelWorkGroupInfo</span></span></a>
        </p>
      </div>
      <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4><img xmlns="http://www.w3.org/1999/xhtml" src="KhronosLogo.jpg" /><p xmlns="http://www.w3.org/1999/xhtml"></p>Copyright © 2007-2010 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
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