sdk/2.1/docs/man/constant.xml

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<refentry>
    <refentryinfo>
        <keywordset>
            <keyword>__constant</keyword>
        </keywordset>
    </refentryinfo>

    <refmeta>
        <refentrytitle>__constant</refentrytitle>

        <refmiscinfo>
            <copyright>
                <year>2007-2013</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="__constant">
        <refname>__constant</refname>

        <refpurpose>
            Address Space Qualifier.
        </refpurpose>
    </refnamediv>

    <!-- ALTERNATIVE SYNTAX SYNOPSIS (NON-FUNCTION) -->

    <refsect2 id="synopsis">
        <title>
        </title>

        <informaltable frame="none">
            <tgroup cols="1" align="left" colsep="0" rowsep="0">
                <colspec colname="col1" colnum="1" />
                <tbody>
                    <row>
                        <entry>
__constant
constant
                        </entry>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
    </refsect2>

<!-- ================================ DESCRIPTION  -->

    <refsect1 id="description"><title>Description</title>
        <para>
          The <function>__constant</function> or <function>constant</function> address space
          name is used to describe variables allocated in global memory and which are accessed
          inside a kernel(s) as read-only variables. These read-only variables can be accessed
          by all (global) work-items of the kernel during its execution.  Pointers to the
          <function>__constant</function> address space are allowed as arguments to functions
          (including kernel functions) and for variables declared inside functions.
        </para>

        <para>
          All string literal storage shall be in the <function>__constant</function> address space.
        </para>

        <para>
          NOTE: Each argument to a kernel that is a pointer to the <function>__constant</function>
          address space is counted separately towards the maximum number of such arguments,
          defined as <constant>CL_DEVICE_MAX_CONSTANT_ARGS</constant> are described in the
          table for <citerefentry><refentrytitle>clGetDeviceInfo</refentrytitle></citerefentry>.
        </para>

        <para>
            Variables in the program scope must be declared in the 
            <function>__constant</function> address space. Variables 
            in the outermost scope of kernel functions can be 
            declared in the <function>__constant</function> address space. 
            These variables are required to be initialized and the 
            values used to initialize these variables must 
            be a compile time constant. Writing to such a variable 
            results in a compile-time error.
        </para>

        <para>
          Implementations are not required to aggregate these declarations into the fewest
          number of constant arguments. This behavior is implementation defined.
        </para>

        <para>
          Thus portable code must conservatively assume that each variable declared inside
          a function or in program scope allocated in the <function>__constant</function>
          address space counts as a separate constant argument.
        </para>
    </refsect1>

<!-- ================================ NOTES  -->

    <refsect1 id="notes"><title>Notes</title>

        &addressSpaceQualifiersInc;

    </refsect1>

<!-- ================================ EXAMPLE  -->

    <refsect2 id="example1">
        <title>
            Example
        </title>

        &qualifierExampleInc;

    </refsect2>

<!-- ================================ SPECIFICATION  -->
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    <refsect1 id="specification"><title>Specification</title>
        <para>
            <imageobject>
                <imagedata fileref="pdficon_small1.gif" format="gif" />
            </imageobject>

            <olink uri="addressSpaceQualifiers">OpenCL Specification</olink>
        </para>
    </refsect1>

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

    <refsect1 id="seealso"><title>Also see</title>
        <para>
            <citerefentry href="global"><refentrytitle>__global</refentrytitle></citerefentry>,
            <citerefentry href="local"><refentrytitle>__local</refentrytitle></citerefentry>,
            <citerefentry href="private"><refentrytitle>__private</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>genericAddressSpace</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>qualifiers</refentrytitle></citerefentry>
        </para>
    </refsect1>

<!-- ============================== COPYRIGHT -->
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    <refsect3 id="Copyright"><title></title>
        <imageobject>
                <imagedata fileref="KhronosLogo.jpg" format="jpg" />
        </imageobject>
        <para />
    </refsect3>

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