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    <title>clCreateCommandQueue</title>
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        <a xmlns="http://www.w3.org/1999/xhtml" id="clCreateCommandQueue"></a>
        <h1>clCreateCommandQueue</h1>
        <p>Create a command-queue on a specific device.</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">cl_command_queue <strong class="fsfunc">clCreateCommandQueue</strong>(</code>
                <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="_top">cl_context</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">context</var>, </td>
              </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="_top">cl_device_id</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">device</var>, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="enums.html#cl_command_queue_properties" target="_top">cl_command_queue_properties</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">properties</var>, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">cl_int</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*errcode_ret</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">context</code>
              </span>
            </dt>
            <dd>
              <p>
                    Must be a valid OpenCL context.
                </p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">device</code>
              </span>
            </dt>
            <dd>
              <p>
                    Must be a device associated with <code class="varname">context</code>. It can either be in the list of devices specified when <code class="varname">context</code> is created using <a class="citerefentry" href="clCreateContext.html"><span class="citerefentry"><span class="refentrytitle">clCreateContext</span></span></a> or have the same device type as the device type specified when the <code class="varname">context</code> is created using <a class="citerefentry" href="clCreateContextFromType.html"><span class="citerefentry"><span class="refentrytitle">clCreateContextFromType</span></span></a>.
                </p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">properties</code>
              </span>
            </dt>
            <dd>
              <p>
					Specifies a list of properties for the command-queue. This is a bit-field. Only command-queue properties specified in the table below can be set in
<code class="varname">properties</code>; otherwise the value specified in <code class="varname">properties</code> is considered to be not valid.
				</p>
              <div class="informaltable">
                <table class="informaltable" border="1">
                  <colgroup>
                    <col align="left" class="col1" />
                    <col align="left" class="col2" />
                  </colgroup>
                  <thead>
                    <tr>
                      <th align="left">Command-Queue Properties</th>
                      <th align="left">Description</th>
                    </tr>
                  </thead>
                  <tbody>
                    <tr>
                      <td align="left">
                        <code class="constant">CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE</code>
                      </td>
                      <td align="left">Determines whether the commands queued in the command-queue are executed in-order or out-of-order. If set, the commands in the command-queue are executed out-of-order. Otherwise, commands are executed in-order.</td>
                    </tr>
                    <tr>
                      <td align="left">
                        <code class="constant">CL_QUEUE_PROFILING_ENABLE</code>
                      </td>
                      <td align="left">Enable or disable profiling of commands in the command-queue. If set, the profiling of commands is enabled. Otherwise profiling of commands is disabled. See  <a class="citerefentry" href="clGetEventProfilingInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetEventProfilingInfo</span></span></a> for more information.</td>
                    </tr>
                  </tbody>
                </table>
              </div>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">errcode_ret</code>
              </span>
            </dt>
            <dd>
              <p>
                    Returns an appropriate error code. If <code class="varname">errcode_ret</code> is <code class="constant">NULL</code>, no error code is returned.
                </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1">
        <a id="notes"></a>
        <h2>Notes</h2>
        <p>The OpenCL functions that are submitted to a command-queue are enqueued in the order the
calls are made but can be configured to execute in-order or out-of-order. The <code class="varname">properties</code>
argument in <code class="function">clCreateCommandQueue</code> can be used to specify the execution order.</p>
        <p>
		If the CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE property of a command-queue is not set, the commands enqueued to a command-queue execute in order. For example, if an application calls <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a> to execute kernel A followed by a <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a> to execute kernel B, the application can assume that kernel A finishes first and then kernel B is executed. If the memory objects output by kernel A are inputs to kernel B then kernel B will see the correct data in memory objects produced by execution of kernel A. If the CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE property of a commandqueue is set, then there is no guarantee that kernel A will finish before kernel B starts execution.
		</p>
        <p>
		Applications can configure the commands enqueued to a command-queue to execute out-of-order by setting the CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE property of the command-queue. This can be specified when the command-queue is created or can be changed dynamically using <code class="function">clCreateCommandQueue</code>. In out-of-order execution mode there is no guarantee that the enqueued commands will finish execution in the order they were queued. As there is no guarantee that kernels will be executed in order, i.e. based on when the <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a> calls are made within a command-queue, it is therefore possible that an earlier <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a> call to execute kernel A identified by event A may execute and/or finish later than a <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a> call to execute kernel B which was called by the application at a later point in time. To guarantee a specific order of execution of kernels, a wait on a particular event (in this case event A) can be used. The wait for event A can be specified in the event_wait_list argument to clEnqueueNDRangeKernel for kernel B.
		</p>
        <p>
		In addition, a wait for events or a barrier command can be enqueued to the command-queue. The wait for events command ensures that previously enqueued commands identified by the list of events to wait for have finished before the next batch of commands is executed. The barrier command ensures that all previously enqueued commands in a command-queue have finished execution before the next batch of commands is executed.
		</p>
        <p>
		Similarly, commands to read, write, copy or map memory objects that are enqueued after
<a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a>, <a class="citerefentry" href="clEnqueueTask.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueTask</span></span></a> or <a class="citerefentry" href="clEnqueueNativeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNativeKernel</span></span></a> commands are not
guaranteed to wait for kernels scheduled for execution to have completed (if the
CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE property is set). To ensure correct
ordering of commands, the event object returned by  <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a>,
clEnqueueTask or <a class="citerefentry" href="clEnqueueNativeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNativeKernel</span></span></a> can be used to enqueue a wait for event or a barrier command can be enqueued that must complete before reads or writes to the memory object(s) occur.
		</p>
      </div>
      <div class="refsect1">
        <a id="errors"></a>
        <h2>Errors</h2>
        <p><code class="function">clCreateCommandQueue</code> returns a valid non-zero command-queue and <code class="varname">errcode_ret</code> is set to <span class="errorname">CL_SUCCESS</span> if the command-queue is created successfully. Otherwise, it returns a NULL value with one of the following error values returned in <code class="varname">errcode_ret</code>:</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_CONTEXT</span> if <code class="varname">context</code> is not a valid context.
		</li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_DEVICE</span> if <code class="varname">device</code> is not a valid device or is not associated with <code class="varname">context</code>.
		</li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_VALUE</span> if values specified in <code class="varname">properties</code> are not valid.
		</li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_QUEUE_PROPERTIES</span> if values specified in <code class="varname">properties</code> are valid but are not supported by 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="refsect1">
        <a id="specification"></a>
        <h2>Specification</h2>
        <p><img src="pdficon_small1.gif" />
            <a href="http://www.khronos.org/registry/cl/specs/opencl-1.0.pdf#page=46" target="OpenCL Spec">OpenCL Specification</a>
        </p>
      </div>
      <div class="refsect1">
        <a id="seealso"></a>
        <h2>Also see</h2>
        <p>
<a class="citerefentry" href="clGetCommandQueueInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetCommandQueueInfo</span></span></a>, 
<a class="citerefentry" href="clReleaseCommandQueue.html"><span class="citerefentry"><span class="refentrytitle">clReleaseCommandQueue</span></span></a>, 
<a class="citerefentry" href="clRetainCommandQueue.html"><span class="citerefentry"><span class="refentrytitle">clRetainCommandQueue</span></span></a>, 
<a class="citerefentry" href="clSetCommandQueueProperty.html"><span class="citerefentry"><span class="refentrytitle">clSetCommandQueueProperty</span></span></a>, 
<a class="citerefentry" href="clCreateContext.html"><span class="citerefentry"><span class="refentrytitle">clCreateContext</span></span></a>, 
<a class="citerefentry" href="clCreateContextFromType.html"><span class="citerefentry"><span class="refentrytitle">clCreateContextFromType</span></span></a>   
        </p>
      </div>
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    Copyright © 2007-2009 The Khronos Group Inc. 
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