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| <title>clCreateCommandQueue</title> |
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| <body> |
| <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. |
| </div> |
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| </html> |
