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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
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Explicit conversions with convert_T()
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<refentrytitle>Explicit conversions with convert_T()</refentrytitle>
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<year>2007-2011</year>
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<holder>The Khronos Group Inc.
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Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and/or associated documentation files (the
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"Materials"), to deal in the Materials without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Materials, and to
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permit persons to whom the Materials are furnished to do so, subject to
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the condition that this copyright notice and permission notice shall be included
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in all copies or substantial portions of the Materials.</holder>
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<manvolnum>3</manvolnum>
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<!-- ================================ SYNOPSIS -->
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<refnamediv id="convert_T">
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<refname>Explicit conversions with convert_T()</refname>
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Explicit type conversions using convert_<varname>T</varname>()
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<!-- ALTERNATIVE SYNTAX SYNOPSIS (NON-FUNCTION) -->
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<refsect2 id="synopsis">
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<informaltable frame="none">
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<tgroup cols="1" align="left" colsep="0" rowsep="0">
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<colspec colname="col1" colnum="1" />
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convert_<replaceable>destType</replaceable>(<replaceable>sourceType</replaceable>)
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<replaceable>destType</replaceable> convert_<replaceable>destType</replaceable><_sat><<replaceable>roundingMode</replaceable>> (<replaceable>sourceType</replaceable>)
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<replaceable>destTypen</replaceable> convert_<replaceable>destTypen</replaceable><_sat><<replaceable>roundingMode</replaceable>> (<replaceable>sourceType</replaceable>)
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<!-- ================================ DESCRIPTION -->
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<refsect1 id="description"><title>Description</title>
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Explicit conversions may be performed using the <code>convert_destType(sourceType)</code>
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suite of functions. These provide a full set of type conversions between
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supported types (see <citerefentry href="scalarDataTypes"><refentrytitle>Scalar Data
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Types</refentrytitle></citerefentry>)<!--section 6.1.1--> except for the following types:
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<type>bool</type>, <type>half</type>, <type>size_t</type>, <type>ptrdiff_t</type>,
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<type>intptr_t</type>, <type>uintptr_t</type>, and <type>void</type>.
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The number of elements in the source and destination vectors must match.
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The behavior of the conversion may be modified by one or two optional modifiers that
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specify saturation for out-of-range inputs and rounding behavior.
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The full form of the scalar convert function is:
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<literallayout> <code><replaceable>destType</replaceable>
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convert_<replaceable>destType</replaceable><_sat><<replaceable>_roundingMode</replaceable>>(<replaceable>sourceType</replaceable>)</code></literallayout>
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The full form of the vector convert function is:
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<literallayout> <code><replaceable>destTypen</replaceable>
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convert_<replaceable>destTypen</replaceable><_sat><<replaceable>_roundingMode</replaceable>>(<replaceable>sourceTypen</replaceable>)</code></literallayout>
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<bridgehead>Data Types</bridgehead>
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Conversions are available for the following scalar types: <type>char</type>,
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<type>uchar</type>, <type>short</type>, <type>ushort</type>, <type>int</type>,
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<type>uint</type>, <type>long</type>, <type>ulong</type>, <type>float</type>, and
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built-in vector types derived therefrom. The operand and result type must have the
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same number of elements. The operand and result type may be the same type in which
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case the conversion has no effect on the type or value of an expression.
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Conversions between integer types follow the conversion rules specified in sections
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6.3.1.1 and 6.3.1.3 of the C99 specification except for out-of-range behavior and
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saturated conversions which are described in section 6.2.3.3 below.
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<bridgehead>Rounding Modes</bridgehead>
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Conversions to and from floating-point type shall conform to IEEE-754 rounding rules.
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Conversions may have an optional rounding mode modifier described in the table below.
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<informaltable frame="all">
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<tgroup cols="2" align="left" colsep="1" rowsep="1">
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<colspec colname="col1" colnum="1" />
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<colspec colname="col2" colnum="2" />
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<entry>Modifier</entry>
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<entry>Rounding Mode Description</entry>
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<entry><para><code>_rte</code></para></entry>
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<entry><para>Round to nearest even</para></entry>
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<entry><para><code>_rtz</code></para></entry>
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<entry><para>Round towards zero</para></entry>
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<entry><para><code>_rtp</code></para></entry>
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<entry><para>Round toward positive infinity</para></entry>
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<entry><para><code>_rtn</code></para></entry>
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<entry><para>Round toward negative infinity</para></entry>
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<entry><para>no modifier specified</para></entry>
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Use the default rounding mode for this destination type,
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<code>_rtz</code> for conversion to integers or the default
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rounding mode for conversion to floating-point types.
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By default, conversions to integer type use the <code>_rtz</code> (round toward zero)
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rounding mode and conversions to floating-point type use the default rounding mode. The
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only default floating-point rounding mode supported is round to nearest even, i.e
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the default rounding mode will be <code>_rte</code> for floating-point types.
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For conversions to floating-point format, when a finite source value exceeds the
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maximum representable finite floating-point destination value, the rounding mode will
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affect whether the result is the maximum finite floating point value or infinity of
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same sign as the source value, per IEEE-754 rules for rounding.
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<bridgehead>Out-of-Range Behavior and Saturated Conversions</bridgehead>
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When the conversion operand is either greater than the greatest representable
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destination value or less than the least representable destination value, it is
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said to be out-of-range. The result of out-of-range conversion is determined by the
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conversion rules specified by the C99 specification in section 6.3. When converting
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from a floating-point type to integer type, the behavior is implementation-defined.
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Conversions to integer type may opt to convert using the optional saturated mode by
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appending the <code>_sat</code> modifier to the conversion function name. When in
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saturated mode, values that are outside the representable range shall clamp to the
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nearest representable value in the destination format. (NaN should be converted to 0).
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Conversions to floating-point type shall conform to IEEE-754 rounding rules. The
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<code>_sat</code> modifier may not be used for conversions to floating-point formats.
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<!-- ================================ NOTES -->
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<refsect1 id="notes"><title>Notes</title>
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<!-- ================================ EXAMPLE -->
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<refsect2 id="example0">
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In the following example, <function>convert_int4</function> converts a
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<type>uchar4</type> vector <code>u</code> to an <type>int4</type> vector <code>c</code>:
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<informaltable frame="none">
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<tgroup cols="1" align="left" colsep="0" rowsep="0">
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<colspec colname="col1" colnum="1" />
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int4 c = convert_int4(u);
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In the following example, <function>convert_int</function> converts a float scalar
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<code>f</code> to an int scalar <code>i</code>:
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<informaltable frame="none">
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<tgroup cols="1" align="left" colsep="0" rowsep="0">
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<colspec colname="col1" colnum="1" />
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int i = convert_int(f);
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<refsect2 id="example1">
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<informaltable frame="none">
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<tgroup cols="1" align="left" colsep="0" rowsep="0">
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<colspec colname="col1" colnum="1" />
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// negative values clamped to 0
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ushort4 u = convert_ushort4_sat( s );
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// values > CHAR_MAX converted to CHAR_MAX
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// values < CHAR_MIN converted to CHAR_MIN
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char4 c = convert_char4_sat( s );
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<refsect2 id="example2">
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<informaltable frame="none">
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<tgroup cols="1" align="left" colsep="0" rowsep="0">
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<colspec colname="col1" colnum="1" />
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// values implementation defined for
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// f > INT_MAX, f < INT_MIN or NaN
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int4 i = convert_int4( f );
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// values > INT_MAX clamp to INT_MAX, values < INT_MIN clamp
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// to INT_MIN. NaN should produce 0.
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// The _rtz rounding mode is
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// used to produce the integer values.
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int4 i2 = convert_int4_sat( f );
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// similar to convert_int4, except that
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// floating-point values are rounded to the nearest
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// integer instead of truncated
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int4 i3 = convert_int4_rte( f );
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// similar to convert_int4_sat, except that
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// floating-point values are rounded to the
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// nearest integer instead of truncated
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int4 i4 = convert_int4_sat_rte( f );
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<refsect2 id="example3">
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<informaltable frame="none">
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<tgroup cols="1" align="left" colsep="0" rowsep="0">
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<colspec colname="col1" colnum="1" />
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// convert ints to floats using the default rounding mode.
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float4 f = convert_float4( i );
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// convert ints to floats. integer values that cannot
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// be exactly represented as floats should round up to the
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// next representable float.
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float4 f = convert_float4_rtp( i );
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<!-- ================================ SPECIFICATION -->
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<!-- Set the "uri" attribute in the <olink /> element to the "named destination" for the PDF page
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<refsect1 id="specification"><title>Specification</title>
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<imagedata fileref="pdficon_small1.gif" format="gif" />
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<olink uri="convert_T">OpenCL Specification</olink>
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<!-- ================================ ALSO SEE -->
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<refsect1 id="seealso"><title>Also see</title>
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<citerefentry href="scalarDataTypes"><refentrytitle>Scalar Data Types</refentrytitle></citerefentry>,
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<citerefentry href="vectorDataTypes"><refentrytitle>Vector Data Types</refentrytitle></citerefentry>
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<!-- ============================== COPYRIGHT -->
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<!-- Content included from copyright.inc.xsl -->
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<refsect3 id="Copyright"><title></title>
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