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    <title>clCreateCommandQueue</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="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"><a class="link" href="abstractDataTypes.html" target="pagedisplay">cl_command_queue</a> <strong class="fsfunc">clCreateCommandQueue</strong>(</code>
                <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="pagedisplay">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="pagedisplay">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="pagedisplay">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="pagedisplay">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 described in the table below. 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 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. See note below for more information.

</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>
          OpenCL objects such as memory, program and kernel objects are created using a
          context.  Operations on these objects are performed using  a command-queue. The
          command-queue can be used to queue a set of operations (referred to as commands)
          in order.  Having multiple command-queues allows applications to queue multiple
          independent commands without requiring synchronization.  Note that this should work
          as long as these objects are not being shared.  Sharing of objects across multiple
          command-queues will require the application to perform appropriate synchronization.
          This is described in Appendix A of the specification.
        </p>
        <h4><a id="id-1.6.3"></a>Out-of-order Execution of Kernels and Memory Object Commands</h4>
        <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 <code class="constant">CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE</code>
          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 <code class="constant">CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE</code> 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 <code class="constant">CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE</code>
          property of the command-queue. This can be specified when the command-queue is
          created. 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, that is 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 <code class="varname">event_wait_list</code> argument to
          <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a>
          for kernel B.
        </p>
        <p>
          In addition, a wait for events
          (<a class="citerefentry" href="clEnqueueMarkerWithWaitList.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueMarkerWithWaitList</span></span></a>)
          or a barrier
          (<a class="citerefentry" href="clEnqueueBarrierWithWaitList.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueBarrierWithWaitList</span></span></a>)
          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 <code class="constant">CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE</code>
          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_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="refsect1">
        <a id="specification"></a>
        <h2>Specification</h2>
        <p><img src="pdficon_small1.gif" />
            <a href="http://www.khronos.org/registry/cl/specs/opencl-1.2.pdf#page=61" 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="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>,
            <a class="citerefentry" href="classDiagram.html"><span class="citerefentry"><span class="refentrytitle">Cardinality Diagram</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 © 2007-2011 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.
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