sdk/1.0/docs/man/local.xml

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<refentry>
    <refentryinfo>
        <keywordset>
            <keyword>                            
                __local
            </keyword>
        </keywordset>
    </refentryinfo>

    <refmeta>                                    
        <refentrytitle>__local</refentrytitle>

        <refmiscinfo>
            <copyright>
                <year>2007-2009</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>2</manvolnum>
    </refmeta>

<!-- ================================ SYNOPSIS -->

    <refnamediv id="__local">             
        <refname>__local</refname>

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


    <!-- ALTERNATIVE SYNTAX SYNOPSIS (NON-FUNCTION) -->
    <refsect2 id="synopsis">
        <title>
        </title>

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                        <entry>
__local
local
                        </entry>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
    </refsect2>


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

    <refsect1 id="description"><title>Description</title>
        <para>
OpenCL implements the following disjoint address spaces: <citerefentry href="global"><refentrytitle>__global</refentrytitle></citerefentry>, <function>__local</function>, <citerefentry href="constant"><refentrytitle>__constant</refentrytitle></citerefentry> and <citerefentry href="private"><refentrytitle>__private</refentrytitle></citerefentry>.
		</para>
        <para>       
The address space qualifier may be used in variable
declarations to specify the region of memory that is used to allocate the object. The C syntax for
type qualifiers is extended in OpenCL to include an address space name as a valid type qualifier.
If the type of an object is qualified by an address space name, the object is allocated in the
specified address name; otherwise, the object is allocated in the generic address space.
        </para>

        <para>
The address space names without the __ prefix i.e.
<function>global</function>,
<function>local</function>,
<function>constant</function> and
<function>private</function>
may be substituted for the corresponding address space names with the __prefix.
        </para>

        <para>
The generic address space name for arguments to a
function in a program, or local variables of a
function is <function>__private</function>.
All arguments to a <function>__kernel</function> function
shall be in the <function>__private</function>
address space.
        </para>

        <para>
<citerefentry  href="functionQualifiers"><refentrytitle>__kernel</refentrytitle></citerefentry> function arguments declared
to be a pointer of a type can point to one of the
following address spaces only:
<function>__global</function>,
<function>__local</function> or
<function>__constant</function>.
A pointer to
address space A can only be assigned to a pointer
to the same address space A. Casting a
pointer to address space A to a pointer to address space B is illegal.
        </para>

        <para>
The <function>__kernel</function> function arguments declared to be of type
<type><citerefentry  href="otherDataTypes"><refentrytitle>image2d_t</refentrytitle></citerefentry></type> or <type><citerefentry  href="otherDataTypes"><refentrytitle>image3d_t</refentrytitle></citerefentry></type>
always point to the <function>__global</function> address space. All program scope variables must be declared in the <function>__constant</function> address space.
        </para>
        <para>
The <function>__local</function> or <function>local</function> address space name
is used to describe variables that need to be allocated in local memory and are shared by all work-items of a work-group. This qualifier can be used with arguments to functions (including <function>__kernel</function> functions) declared as pointers, or with variables defined inside a <function>__kernel</function> function.
        </para>
    </refsect1>


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

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

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                        <entry>
// declares a pointer p in the __private address space that
// points to an int object in address space __global
__global int *p;

// declares an array of 4 floats in the __private address space.
float x[4];
                        </entry>
                    </row>
                </tbody>
            </tgroup>
        </informaltable>
    </refsect2>



<!-- ================================ SPECIFICATION  -->
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    <refsect1 id="specification"><title>Specification</title>
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            <olink uri="addressSpaceQualifier">OpenCL Specification</olink>
        </para>
    </refsect1>


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

    <refsect1 id="seealso"><title>Also see</title>
        <para>
            <citerefentry href="global"><refentrytitle>__global</refentrytitle></citerefentry>, 
            <citerefentry href="constant"><refentrytitle>__constant</refentrytitle></citerefentry>, 
            <citerefentry href="private"><refentrytitle>__private</refentrytitle></citerefentry>
        </para>
    </refsect1>



<!-- ============================== COPYRIGHT -->
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