sdk/1.2/docs/man/clCreateCommandQueue.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
              "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry>
    <refentryinfo>
        <keywordset><keyword>clCreateCommandQueue</keyword></keywordset>
    </refentryinfo>
    <refmeta>
        <refentrytitle>clCreateCommandQueue</refentrytitle>
        <refmiscinfo>
            <copyright>
                <year>2007-2011</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="clCreateCommandQueue">
<refname>clCreateCommandQueue</refname>
           <refpurpose>Create a command-queue on a specific device.</refpurpose>
    </refnamediv>
    <refsynopsisdiv xmlns:xlink="http://www.w3.org/1999/xlink"><title></title>
        <funcsynopsis>
            <funcprototype>
                <funcdef><link xlink:href="abstractDataTypes.html">cl_command_queue</link> <function>clCreateCommandQueue</function></funcdef>
                <paramdef><link xlink:href="abstractDataTypes.html">cl_context</link><parameter>context</parameter></paramdef>
                <paramdef><link xlink:href="abstractDataTypes.html">cl_device_id</link><parameter>device</parameter></paramdef>
                <paramdef><link xlink:href="enums.html#cl_command_queue_properties">cl_command_queue_properties</link><parameter>properties</parameter></paramdef>
                <paramdef><link xlink:href="scalarDataTypes.html">cl_int</link><parameter>*errcode_ret</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>context</varname></term>
            <listitem>
                <para>
                    Must be a valid OpenCL context.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><varname>device</varname></term>
            <listitem>
                <para>
                    Must be a device associated with <varname>context</varname>. It can either be in the list of devices specified when <varname>context</varname> is created using <citerefentry><refentrytitle>clCreateContext</refentrytitle></citerefentry> or have the same device type as the device type specified when the <varname>context</varname> is created using <citerefentry><refentrytitle>clCreateContextFromType</refentrytitle></citerefentry>.
                </para>
            </listitem>
        </varlistentry>

<!-- ================================ PARAMETER TABLE (OPTIONAL) -->
<!-- DELETE IF NOT NEEDED -->
<!-- Use this if parameter information requires a table. Adjust the number of columns by adjusting
<colspec /> tags. Column header goes in the <thead /> section. Delte the section if no column head needed.
-->
        <varlistentry>
            <term><varname>properties</varname></term>
            <listitem>
                <para>
                    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
<varname>properties</varname>; otherwise the value specified in <varname>properties</varname> is considered to be not valid.
                </para>

                <!-- table 5.1 -->
                <informaltable frame="all"><tgroup cols="2" align="left" colsep="1" rowsep="1">
    <colspec colname="col1" colnum="1" />
    <colspec colname="col2" colnum="2" />
    <thead>
        <row>
        <entry>Command-Queue Properties</entry>
        <entry>Description</entry>
        </row>
    </thead>
    <tbody>
        <row>
            <entry><constant>CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE</constant></entry>
            <entry>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.

</entry>
        </row>
        <row>
            <entry><constant>CL_QUEUE_PROFILING_ENABLE</constant></entry>
            <entry>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  <citerefentry><refentrytitle>clGetEventProfilingInfo</refentrytitle></citerefentry> for more information.</entry>
        </row>
    </tbody>

    </tgroup></informaltable>
            </listitem>
        </varlistentry>
<!-- ================================ END PARAMETER TABLE  -->


        <varlistentry>
            <term><varname>errcode_ret</varname></term>
            <listitem>
                <para>
                    Returns an appropriate error code. If <varname>errcode_ret</varname> is <constant>NULL</constant>, no error code is returned.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>

<!-- ================================ NOTES  -->
    <refsect1 id="notes"><title>Notes</title>
        <para>
          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.
        </para>

        <bridgehead>Out-of-order Execution of Kernels and Memory Object Commands</bridgehead>

        <para>
          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
          <varname>properties</varname> argument in <function>clCreateCommandQueue</function>
          can be used to specify the execution order.
        </para>

        <para>
          If the <constant>CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE</constant>
          property of a command-queue is not set, the commands enqueued to a
          command-queue execute in order. For example, if an application calls
          <citerefentry><refentrytitle>clEnqueueNDRangeKernel</refentrytitle></citerefentry>
          to execute kernel A followed by a
          <citerefentry><refentrytitle>clEnqueueNDRangeKernel</refentrytitle></citerefentry>
          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 <constant>CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE</constant> property
          of a commandqueue is set, then there is no guarantee that kernel A will finish before
          kernel B starts execution.
        </para>

        <para>
          Applications can configure the commands enqueued to a command-queue to execute
          out-of-order by setting the <constant>CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE</constant>
          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
          <citerefentry><refentrytitle>clEnqueueNDRangeKernel</refentrytitle></citerefentry>
          calls are made within a command-queue, it is therefore possible that an earlier
          <citerefentry><refentrytitle>clEnqueueNDRangeKernel</refentrytitle></citerefentry>
          call to execute kernel A identified by event A may execute and/or finish later than a
          <citerefentry><refentrytitle>clEnqueueNDRangeKernel</refentrytitle></citerefentry>
          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 <varname>event_wait_list</varname> argument to
          <citerefentry><refentrytitle>clEnqueueNDRangeKernel</refentrytitle></citerefentry>
          for kernel B.
        </para>

        <para>
          In addition, a wait for events
          (<citerefentry><refentrytitle>clEnqueueMarkerWithWaitList</refentrytitle></citerefentry>)
          or a barrier
          (<citerefentry><refentrytitle>clEnqueueBarrierWithWaitList</refentrytitle></citerefentry>)
          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.
        </para>

        <para>
          Similarly, commands to read, write, copy or map memory objects that are enqueued after
          <citerefentry><refentrytitle>clEnqueueNDRangeKernel</refentrytitle></citerefentry>,
          <citerefentry><refentrytitle>clEnqueueTask</refentrytitle></citerefentry> or
          <citerefentry><refentrytitle>clEnqueueNativeKernel</refentrytitle></citerefentry>
          commands are not guaranteed to wait for kernels scheduled for execution to have
          completed (if the <constant>CL_QUEUE_OUT_OF_ORDER_EXEC_MODE_ENABLE</constant>
          property is set). To ensure correct ordering of commands, the event object returned by
          <citerefentry><refentrytitle>clEnqueueNDRangeKernel</refentrytitle></citerefentry>,
          clEnqueueTask or
          <citerefentry><refentrytitle>clEnqueueNativeKernel</refentrytitle></citerefentry>
          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.
        </para>
    </refsect1>

<!-- ================================ ERRORS  -->

  <refsect1 id="errors"><title>Errors</title>
    <para>
      <function>clCreateCommandQueue</function> returns a valid non-zero command-queue and
      <varname>errcode_ret</varname> is set to <errorname>CL_SUCCESS</errorname> if the
      command-queue is created successfully. Otherwise, it returns a NULL value with one
      of the following error values returned in <varname>errcode_ret</varname>:
    </para>

    <itemizedlist mark="disc">
      <listitem>
        <errorname>CL_INVALID_CONTEXT</errorname> if <varname>context</varname> is not a valid
        context.
      </listitem>

      <listitem>
        <errorname>CL_INVALID_DEVICE</errorname> if <varname>device</varname> is not a valid
        device or is not associated with <varname>context</varname>.
      </listitem>

      <listitem>
        <errorname>CL_INVALID_VALUE</errorname> if values specified in
        <varname>properties</varname> are not valid.
      </listitem>

      <listitem>
        <errorname>CL_INVALID_QUEUE_PROPERTIES</errorname> if values specified in
        <varname>properties</varname> are valid but are not supported by the device.
      </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>
                            Example goes here - it will be set in "code" type with white space preserved.
                        </entry>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
    </refsect2>
-->

<!-- ================================ SPECIFICATION  -->
<!-- Set the "uri" attribute in the <olink /> element to the "named destination" for the PDF page
-->

    <refsect1 id="specification"><title>Specification</title>
        <para><imageobject><imagedata fileref="pdficon_small1.gif" format="gif" /></imageobject>
            <olink uri="clCreateCommandQueue">OpenCL Specification</olink>
        </para>
    </refsect1>

<!-- ================================ ALSO SEE  -->

    <refsect1 id="seealso"><title>Also see</title>
        <para>
            <citerefentry><refentrytitle>clGetCommandQueueInfo</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>clReleaseCommandQueue</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>clRetainCommandQueue</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>clCreateContext</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>clCreateContextFromType</refentrytitle></citerefentry>,
            <citerefentry href="classDiagram"><refentrytitle>Cardinality Diagram</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>


<!-- 27-Oct-2011 -->
</refentry>