| <?xml version="1.0" encoding="UTF-8"?> | |
| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd"> | |
| <!-- saved from url=(0013)about:internet --> | |
| <?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" xmlns:xlink="http://www.w3.org/1999/xlink" pref:renderer="mathplayer-dl"> | |
| <head> | |
| <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> | |
| <style xmlns="" type="text/css"> | |
| /* This style sets a margin around the entire page */ | |
| html, body { | |
| margin: 10px; | |
| } | |
| p { | |
| font: normal 16px verdana, sans-serif; | |
| margin: 0; | |
| padding-bottom:12px; | |
| } | |
| h1 { | |
| font: bold 25px verdana, sans-serif; | |
| margin-top: 0; | |
| margin-bottom: 3px; | |
| padding-top: 0; | |
| padding-bottom: 0; | |
| } | |
| h2 { | |
| font: bold 19px verdana, sans-serif; | |
| margin-top: 28px; | |
| margin-bottom: 3px; | |
| padding-top: 0; | |
| padding-bottom: 0; | |
| } | |
| h3 { | |
| font: bold 19px verdana, sans-serif !important; | |
| margin-top: 28px; | |
| margin-bottom: 3px; | |
| padding-top: 0; | |
| padding-bottom: 0; | |
| } | |
| li { | |
| font: normal 16px verdana, sans-serif; | |
| margin-top: 0; | |
| margin-bottom: 18px; | |
| padding-top: 0; | |
| padding-bottom: 0; | |
| } | |
| .pdparam { | |
| font: italic 16px verdana, sans-serif; | |
| } | |
| .term { | |
| font: italic 16px verdana, sans-serif; | |
| font-weight: normal; | |
| } | |
| .type { | |
| font: normal 16px verdana, sans-serif !important; | |
| } | |
| .parameter { | |
| font-style: italic; | |
| } | |
| a:link, a:visited { | |
| color: blue; | |
| text-decoration: none; | |
| font: normal 16px; | |
| } | |
| a:hover { | |
| background-color: #FFFF99; | |
| font: normal 16px; | |
| } | |
| div.funcsynopsis { | |
| text-align: left; | |
| background-color: #e6e6e6; | |
| font: normal 16px verdana, sans-serif; | |
| padding-top: 10px; | |
| padding-bottom: 10px; | |
| } | |
| div.funcsynopsis table { | |
| border-collapse: separate; | |
| font: normal 16px verdana, sans-serif; | |
| } | |
| div.funcsynopsis td { | |
| background-color: #e6e6e6; | |
| border: 0 solid #000; | |
| padding: 1px; | |
| font: normal 16px verdana, sans-serif; | |
| } | |
| div.refsect1 { | |
| font-family: verdana, sans-serif; | |
| font-size: 16px; | |
| } | |
| code.constant { | |
| font: normal 16px courier new, monospace !important; | |
| } | |
| span.errorname { | |
| font: normal 16px verdana, sans-serif !important; | |
| } | |
| code.function { | |
| font: bold 16px verdana, sans-serif !important; | |
| } | |
| b.fsfunc { | |
| font: bold 16px verdana, sans-serif !important; | |
| } | |
| code.varname { | |
| font: italic 16px verdana, sans-serif; | |
| } | |
| code.replaceable { | |
| font: italic 16px courier new, monospace; | |
| } | |
| code.funcdef { | |
| font: normal 16px verdana, sans-serif !important; | |
| } | |
| .citerefentry { | |
| font: normal 16px verdana, sans-serif !important; | |
| } | |
| .parameter { | |
| font-style: italic; | |
| } | |
| code.fsfunc { | |
| font: normal 16px verdana, sans-serif !important; | |
| } | |
| /* PARAMETER: This style controls spacing between the terms in Parameter section */ | |
| dt { | |
| margin-top: 15px; | |
| } | |
| /* TABLES: These styles apply to all tables OTHER than the Synopsis and Example tables */ | |
| div.refsect1 table { | |
| width: 100%; | |
| margin-top: 10px; | |
| background-color: #FFF; | |
| border-collapse: collapse; | |
| border-color: #000; | |
| border-width: 1px; | |
| font: normal 16px verdana, sans-serif; | |
| } | |
| div.refsect1 th { | |
| border-collapse: collapse; | |
| border-color: #000; | |
| border-width: 1px; | |
| font: bold 16px verdana, sans-serif; | |
| } | |
| div.refsect1 td { | |
| background-color: #FFF; | |
| padding: 5px; | |
| vertical-align: text-top; | |
| border-collapse: collapse; | |
| border-color: #000; | |
| border-width: 1px; | |
| font: normal 16px verdana, sans-serif; | |
| } | |
| div.refsect1 p{ | |
| font: normal 16px verdana, sans-serif; | |
| margin-top: 8px; | |
| margin-bottom: 8px; | |
| padding-top: 0; | |
| padding-bottom: 0; | |
| } | |
| /* EXAMPLE: These styles apply only to the Example section */ | |
| div.refsect2 { | |
| font: normal 16px courier new, monospace !important; | |
| } | |
| div.refsect2 table { | |
| margin-top: 0; | |
| background-color: #e6e6e6; | |
| width: 100%; | |
| border: 0 solid #000; | |
| padding: 2px; | |
| font: normal 16px courier new, monospace !important; | |
| } | |
| div.refsect2 td { | |
| background-color: #e6e6e6; | |
| font: normal 16px courier new, monospace !important; | |
| white-space:pre; | |
| } | |
| /* COPYRIGHT: This style formats the text of the copyright statement at the bottom of the page */ | |
| div.refsect3 { | |
| font: normal 11px verdana, sans-serif; | |
| margin-top: 50px; | |
| margin-bottom: 20px; | |
| padding-top: 0; | |
| padding-bottom: 0; | |
| } | |
| </style> | |
| <title>Function Qualifiers</title> | |
| <meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /> | |
| <meta name="keywords" content=" Function Qualifiers " /> | |
| </head> | |
| <body> | |
| <div class="refentry"> | |
| <a id="idm1"></a> | |
| <div class="titlepage"></div> | |
| <div xmlns="" class="refnamediv"> | |
| <a xmlns="http://www.w3.org/1999/xhtml" id="Function Qualifiers"></a> | |
| <h1>Function Qualifiers</h1> | |
| <p> | |
| Qualifiers for kernel functions. | |
| </p> | |
| </div> | |
| <div class="refsect2"> | |
| <a id="synopsis"></a> | |
| <h3> | |
| </h3> | |
| <div class="informaltable"> | |
| <table class="informaltable" border="0"> | |
| <colgroup> | |
| <col align="left" class="col1" /> | |
| </colgroup> | |
| <tbody> | |
| <tr> | |
| <td align="left"> | |
| __kernel | |
| kernel | |
| __attribute__((vec_type_hint(<type<span class="emphasis"><em>n</em></span>>))) | |
| __attribute__((work_group_size_hint(<span class="emphasis"><em>X</em></span>, <span class="emphasis"><em>Y</em></span>, <span class="emphasis"><em>Z</em></span>))) | |
| __attribute__((reqd_work_group_size(<span class="emphasis"><em>X</em></span>, <span class="emphasis"><em>Y</em></span>, <span class="emphasis"><em>Z</em></span>))) | |
| </td> | |
| </tr> | |
| </tbody> | |
| </table> | |
| </div> | |
| </div> | |
| <div class="refsect1"> | |
| <a id="description"></a> | |
| <h2>Description</h2> | |
| <p> | |
| The <code class="function">__kernel</code> (or <code class="function">kernel</code>) qualifier | |
| declares a function to be a kernel that can be | |
| executed by an application on an OpenCL device(s). | |
| The following rules apply to functions that | |
| are declared with this qualifier: | |
| </p> | |
| <div class="itemizedlist"> | |
| <ul class="itemizedlist" style="list-style-type: bullet; "> | |
| <li class="listitem" style="list-style-type: disc"> | |
| <p> | |
| It can be executed on the device only | |
| </p> | |
| </li> | |
| <li class="listitem" style="list-style-type: disc"> | |
| <p> | |
| It can be called by the host | |
| </p> | |
| </li> | |
| <li class="listitem" style="list-style-type: disc"> | |
| <p> | |
| It is just a regular function call if a <code class="function">__kernel</code> | |
| function is called by another kernel function. | |
| </p> | |
| </li> | |
| </ul> | |
| </div> | |
| <p> | |
| The <code class="function">__kernel</code> qualifier can be used with the keyword | |
| <a class="citerefentry" href="attribute.html"><span class="citerefentry"><span class="refentrytitle">__attribute__</span></span></a> to declare additional | |
| information about the kernel function as described below. | |
| </p> | |
| <p> | |
| The optional | |
| <code class="constant">__attribute__((vec_type_hint(<type<span class="emphasis"><em>n</em></span>>)))</code> | |
| is a hint to the | |
| compiler and is intended to be a representation of the computational | |
| <span class="emphasis"><em>width</em></span> of the | |
| <code class="function">__kernel</code>, | |
| and should serve as the basis for calculating processor | |
| bandwidth utilization when the compiler | |
| is looking to autovectorize the code. | |
| <code class="constant">vec_type_hint (<type<span class="emphasis"><em>n</em></span>>)</code> | |
| shall be one of the built-in scalar or vector data type described in | |
| tables 6.1 and 6.2. | |
| If | |
| <code class="constant">vec_type_hint (<type<span class="emphasis"><em>n</em></span>>)</code> | |
| is not specified, the default value is <span class="type">int</span>. | |
| </p> | |
| <p> | |
| The | |
| <code class="constant">__attribute__((vec_type_hint(int)))</code> | |
| is the default type. | |
| </p> | |
| <p> | |
| For example, where the developer specified a width of <span class="type">float4</span>, | |
| the compiler should assume | |
| that the computation usually uses up 4 lanes of a float vector, | |
| and would decide to merge work-items or possibly even separate | |
| one work-item into many threads to better match the hardware | |
| capabilities. A conforming implementation is not required | |
| to autovectorize code, but shall | |
| support the hint. A compiler may autovectorize, even if no | |
| hint is provided. If an | |
| implementation merges <code class="constant">N</code> work-items into one thread, | |
| it is responsible for correctly handling | |
| cases where the number of global or local work-items | |
| in any dimension modulo <code class="constant">N</code> is not zero. | |
| </p> | |
| <p> | |
| If for example, a <code class="function">__kernel</code> is declared with | |
| <code class="constant">__attribute__(( vec_type_hint (float4)))</code> | |
| (meaning that most operations in the <code class="function">__kernel</code> | |
| are explicitly vectorized using | |
| <span class="type">float4</span>) and the kernel is running using | |
| Intel® Advanced Vector Instructions | |
| (Intel® AVX) | |
| which implements a 8-float-wide vector unit, | |
| the autovectorizer might choose to merge two | |
| work-items to one thread, running a second | |
| work-item in the high half of the 256-bit AVX | |
| register. | |
| </p> | |
| <p> | |
| As another example, a Power4 machine has two scalar | |
| double precision floating-point units with | |
| an 6-cycle deep pipe. An autovectorizer for the | |
| Power4 machine might choose to interleave six | |
| <code class="constant">__attribute__(( vec_type_hint (double2))) __kernel</code>s | |
| into one hardware | |
| thread, to ensure that there is always 12-way | |
| parallelism available to saturate the FPUs. It might | |
| also choose to merge 4 or 8 work-items (or some | |
| other number) if it concludes that these are | |
| better choices, due to resource utilization | |
| concerns or some preference for divisibility by 2. | |
| </p> | |
| <p> | |
| The optional | |
| <code class="constant">__attribute__((work_group_size_hint(<span class="emphasis"><em>X</em></span>, <span class="emphasis"><em>Y</em></span>, <span class="emphasis"><em>Z</em></span>)))</code> | |
| is a hint to the | |
| compiler and is intended to specify the work-group size | |
| that may be used i.e. value most likely to | |
| be specified by the <code class="varname">local_work_size</code> argument to | |
| <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a>. | |
| For example the | |
| <code class="constant">__attribute__((work_group_size_hint(1, 1, 1)))</code> | |
| is a hint to the compiler | |
| that the kernel will most likely be executed | |
| with a work-group size of 1. | |
| </p> | |
| <p> | |
| The optional | |
| <code class="constant">__attribute__((reqd_work_group_size(<span class="emphasis"><em>X</em></span>, <span class="emphasis"><em>Y</em></span>, <span class="emphasis"><em>Z</em></span>)))</code> | |
| is the work-group size that must be used as the | |
| <code class="varname">local_work_size</code> argument to | |
| <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a>. | |
| This allows the compiler to optimize the generated | |
| code appropriately for this kernel. The optional | |
| <code class="constant">__attribute__((reqd_work_group_size(<span class="emphasis"><em>X</em></span>, <span class="emphasis"><em>Y</em></span>, <span class="emphasis"><em>Z</em></span>)))</code>, | |
| if specified, must be (1, 1, 1) if the kernel is executed via | |
| <a class="citerefentry" href="clEnqueueTask.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueTask</span></span></a>. | |
| </p> | |
| <p> | |
| If <code class="varname">Z</code> is one, the <code class="varname">work_dim</code> argument to | |
| <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a> | |
| can be 2 or 3. If <code class="varname">Y</code> and <code class="varname">Z</code> are | |
| one, the <code class="varname">work_dim</code> argument to | |
| <a class="citerefentry" href="clEnqueueNDRangeKernel.html"><span class="citerefentry"><span class="refentrytitle">clEnqueueNDRangeKernel</span></span></a> | |
| can be 1, 2 or 3. | |
| </p> | |
| </div> | |
| <div class="refsect1"> | |
| <a id="notes"></a> | |
| <h2>Notes</h2> | |
| <p> | |
| Implicit in autovectorization is the assumption that | |
| any libraries called from the | |
| __kernel must be recompilable at | |
| run time to handle cases where the compiler decides to | |
| merge or separate workitems. This probably means that such | |
| libraries can never be hard coded binaries or that hard | |
| coded binaries must be accompanied either by source or some | |
| retargetable intermediate representation. This may be | |
| a code security question for some. | |
| </p> | |
| </div> | |
| <div class="refsect2"> | |
| <a id="example1"></a> | |
| <h3> | |
| Example | |
| </h3> | |
| <div class="informaltable"> | |
| <table class="informaltable" border="0"> | |
| <colgroup> | |
| <col align="left" class="col1" /> | |
| </colgroup> | |
| <tbody> | |
| <tr> | |
| <td align="left"> | |
| // autovectorize assuming float4 as the | |
| // basic computation width | |
| __kernel __attribute__((vec_type_hint(float4))) | |
| void foo( __global float4 *p ) { .... | |
| // autovectorize assuming double as the | |
| // basic computation width | |
| __kernel __attribute__((vec_type_hint(double))) | |
| void foo( __global float4 *p ){ .... | |
| // autovectorize assuming int (default) | |
| // as the basic computation width | |
| __kernel | |
| void foo( __global float4 *p ){ .... | |
| </td> | |
| </tr> | |
| </tbody> | |
| </table> | |
| </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=154" target="OpenCL Spec">OpenCL Specification</a> | |
| </p> | |
| </div> | |
| <div class="refsect1"> | |
| <a id="seealso"></a> | |
| <h2>Also see</h2> | |
| <p> | |
| <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> | |
| </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 © 2007-2009 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> | |
| </div> | |
| </body> | |
| </html> |