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| <refentry> |
| <refentryinfo> |
| <keywordset> |
| <keyword>Explicit conversions with convert_T()</keyword> |
| </keywordset> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle>Explicit conversions with convert_T()</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="convert_T"> |
| <refname>Explicit conversions with convert_T()</refname> |
| |
| <refpurpose> |
| Explicit type conversions using convert_<varname>T</varname>() |
| </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> |
| convert_<replaceable>destType</replaceable>(<replaceable>sourceType</replaceable>) |
| <replaceable>destType</replaceable> convert_<replaceable>destType</replaceable><_sat><<replaceable>roundingMode</replaceable>> (<replaceable>sourceType</replaceable>) |
| <replaceable>destTypen</replaceable> convert_<replaceable>destTypen</replaceable><_sat><<replaceable>roundingMode</replaceable>> (<replaceable>sourceType</replaceable>) |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| </refsect2> |
| |
| <!-- ================================ DESCRIPTION --> |
| |
| <refsect1 id="description"><title>Description</title> |
| <para> |
| Explicit conversions may be performed using the <code>convert_destType(sourceType)</code> |
| suite of functions. These provide a full set of type conversions between |
| supported types (see <citerefentry href="scalarDataTypes"><refentrytitle>Scalar Data |
| Types</refentrytitle></citerefentry>)<!--section 6.1.1--> except for the following types: |
| <type>bool</type>, <type>half</type>, <type>size_t</type>, <type>ptrdiff_t</type>, |
| <type>intptr_t</type>, <type>uintptr_t</type>, and <type>void</type>. |
| </para> |
| |
| <para> |
| The number of elements in the source and destination vectors must match. |
| </para> |
| |
| <para> |
| The behavior of the conversion may be modified by one or two optional modifiers that |
| specify saturation for out-of-range inputs and rounding behavior. |
| </para> |
| |
| <para> |
| The full form of the scalar convert function is: |
| <literallayout> <code><replaceable>destType</replaceable> |
| convert_<replaceable>destType</replaceable><_sat><<replaceable>_roundingMode</replaceable>>(<replaceable>sourceType</replaceable>)</code></literallayout> |
| </para> |
| |
| <para> |
| The full form of the vector convert function is: |
| <literallayout> <code><replaceable>destTypen</replaceable> |
| convert_<replaceable>destTypen</replaceable><_sat><<replaceable>_roundingMode</replaceable>>(<replaceable>sourceTypen</replaceable>)</code></literallayout> |
| </para> |
| |
| <bridgehead>Data Types</bridgehead> |
| |
| <para> |
| Conversions are available for the following scalar types: <type>char</type>, |
| <type>uchar</type>, <type>short</type>, <type>ushort</type>, <type>int</type>, |
| <type>uint</type>, <type>long</type>, <type>ulong</type>, <type>float</type>, and |
| built-in vector types derived therefrom. The operand and result type must have the |
| same number of elements. The operand and result type may be the same type in which |
| case the conversion has no effect on the type or value of an expression. |
| </para> |
| |
| <para> |
| Conversions between integer types follow the conversion rules specified in sections |
| 6.3.1.1 and 6.3.1.3 of the C99 specification except for out-of-range behavior and |
| saturated conversions which are described in section 6.2.3.3 below. |
| </para> |
| |
| <bridgehead>Rounding Modes</bridgehead> |
| |
| <para> |
| Conversions to and from floating-point type shall conform to IEEE-754 rounding rules. |
| Conversions may have an optional rounding mode modifier described in the table below. |
| </para> |
| |
| <para> |
| <informaltable frame="all"> |
| <tgroup cols="2" align="left" colsep="1" rowsep="1"> |
| <colspec colname="col1" colnum="1" /> |
| <colspec colname="col2" colnum="2" /> |
| |
| <thead> |
| <row> |
| <entry>Modifier</entry> |
| <entry>Rounding Mode Description</entry> |
| </row> |
| </thead> |
| |
| <tbody> |
| <row> |
| <entry><para><code>_rte</code></para></entry> |
| <entry><para>Round to nearest even</para></entry> |
| </row> |
| |
| <row> |
| <entry><para><code>_rtz</code></para></entry> |
| <entry><para>Round towards zero</para></entry> |
| </row> |
| |
| <row> |
| <entry><para><code>_rtp</code></para></entry> |
| <entry><para>Round toward positive infinity</para></entry> |
| </row> |
| |
| <row> |
| <entry><para><code>_rtn</code></para></entry> |
| <entry><para>Round toward negative infinity</para></entry> |
| </row> |
| |
| <row> |
| <entry><para>no modifier specified</para></entry> |
| <entry> |
| <para> |
| Use the default rounding mode for this destination type, |
| <code>_rtz</code> for conversion to integers or the default |
| rounding mode for conversion to floating-point types. |
| </para> |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| </para> |
| |
| <para> |
| By default, conversions to integer type use the <code>_rtz</code> (round toward zero) |
| rounding mode and conversions to floating-point type use the default rounding mode. The |
| only default floating-point rounding mode supported is round to nearest even, i.e |
| the default rounding mode will be <code>_rte</code> for floating-point types. |
| </para> |
| |
| <para> |
| For conversions to floating-point format, when a finite source value exceeds the |
| maximum representable finite floating-point destination value, the rounding mode will |
| affect whether the result is the maximum finite floating point value or infinity of |
| same sign as the source value, per IEEE-754 rules for rounding. |
| </para> |
| |
| <para> |
| <bridgehead>Out-of-Range Behavior and Saturated Conversions</bridgehead> |
| </para> |
| |
| <para> |
| When the conversion operand is either greater than the greatest representable |
| destination value or less than the least representable destination value, it is |
| said to be out-of-range. The result of out-of-range conversion is determined by the |
| conversion rules specified by the C99 specification in section 6.3. When converting |
| from a floating-point type to integer type, the behavior is implementation-defined. |
| </para> |
| |
| <para> |
| Conversions to integer type may opt to convert using the optional saturated mode by |
| appending the <code>_sat</code> modifier to the conversion function name. When in |
| saturated mode, values that are outside the representable range shall clamp to the |
| nearest representable value in the destination format. (NaN should be converted to 0). |
| </para> |
| |
| <para> |
| Conversions to floating-point type shall conform to IEEE-754 rounding rules. The |
| <code>_sat</code> modifier may not be used for conversions to floating-point formats. |
| </para> |
| </refsect1> |
| |
| <!-- ================================ NOTES --> |
| |
| <refsect1 id="notes"><title>Notes</title> |
| <!-- from API spec, Appendix B --> |
| OpenCL provides <code>convert_</code> operators for conversion between all types. C99 does not |
| define what happens when a floating-point type is converted to integer type and the |
| floating-point value lies outside the representable range of the integer type after rounding. |
| When the <code>_sat</code> variant of the conversion is used, the float shall be converted to the |
| nearest representable integer value. Similarly, OpenCL also makes recommendations |
| about what should happen with NaN. Hardware manufacturers that provide the saturated |
| conversion in hardware may use the saturated conversion hardware for both the saturated |
| and non-saturated versions of the OpenCL <code>convert_</code> operator. OpenCL does not |
| define what happens for the non-saturated conversions when floating-point operands are |
| outside the range representable integers after rounding. |
| </refsect1> |
| |
| <!-- ================================ EXAMPLE --> |
| |
| <refsect2 id="example0"> |
| <title> |
| Examples |
| </title> |
| |
| <para> |
| In the following example, <function>convert_int4</function> converts a |
| <type>uchar4</type> vector <code>u</code> to an <type>int4</type> vector <code>c</code>: |
| </para> |
| |
| <informaltable frame="none"> |
| <tgroup cols="1" align="left" colsep="0" rowsep="0"> |
| <colspec colname="col1" colnum="1" /> |
| <tbody> |
| <row> |
| <entry> |
| uchar4 u; |
| int4 c = convert_int4(u); |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| |
| <para> |
| In the following example, <function>convert_int</function> converts a float scalar |
| <code>f</code> to an int scalar <code>i</code>: |
| </para> |
| |
| <informaltable frame="none"> |
| <tgroup cols="1" align="left" colsep="0" rowsep="0"> |
| <colspec colname="col1" colnum="1" /> |
| <tbody> |
| <row> |
| <entry> |
| float f; |
| int i = convert_int(f); |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| </refsect2> |
| |
| <refsect2 id="example1"> |
| <title> |
| </title> |
| |
| <para> |
| Example: |
| </para> |
| |
| <informaltable frame="none"> |
| <tgroup cols="1" align="left" colsep="0" rowsep="0"> |
| <colspec colname="col1" colnum="1" /> |
| <tbody> |
| <row> |
| <entry> |
| short4 s; |
| |
| // negative values clamped to 0 |
| ushort4 u = convert_ushort4_sat( s ); |
| |
| // values > CHAR_MAX converted to CHAR_MAX |
| // values < CHAR_MIN converted to CHAR_MIN |
| char4 c = convert_char4_sat( s ); |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| </refsect2> |
| |
| <refsect2 id="example2"> |
| <title> |
| </title> |
| |
| <para> |
| Example: |
| </para> |
| |
| <informaltable frame="none"> |
| <tgroup cols="1" align="left" colsep="0" rowsep="0"> |
| <colspec colname="col1" colnum="1" /> |
| <tbody> |
| <row> |
| <entry> |
| float4 f; |
| |
| // values implementation defined for |
| // f > INT_MAX, f < INT_MIN or NaN |
| int4 i = convert_int4( f ); |
| |
| // values > INT_MAX clamp to INT_MAX, values < INT_MIN clamp |
| // to INT_MIN. NaN should produce 0. |
| |
| // The _rtz rounding mode is |
| // used to produce the integer values. |
| int4 i2 = convert_int4_sat( f ); |
| |
| // similar to convert_int4, except that |
| // floating-point values are rounded to the nearest |
| // integer instead of truncated |
| int4 i3 = convert_int4_rte( f ); |
| |
| // similar to convert_int4_sat, except that |
| // floating-point values are rounded to the |
| // nearest integer instead of truncated |
| int4 i4 = convert_int4_sat_rte( f ); |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| </refsect2> |
| |
| <refsect2 id="example3"> |
| <title> |
| </title> |
| |
| <para> |
| Example: |
| </para> |
| |
| <informaltable frame="none"> |
| <tgroup cols="1" align="left" colsep="0" rowsep="0"> |
| <colspec colname="col1" colnum="1" /> |
| <tbody> |
| <row> |
| <entry> |
| int4 i; |
| |
| // convert ints to floats using the default rounding mode. |
| float4 f = convert_float4( i ); |
| |
| // convert ints to floats. integer values that cannot |
| // be exactly represented as floats should round up to the |
| // next representable float. |
| float4 f = convert_float4_rtp( i ); |
| </entry> |
| </row> |
| </tbody> |
| </tgroup> |
| </informaltable> |
| </refsect2> |
| |
| <!-- ================================ SPECIFICATION --> |
| <!-- Set the "uri" attribute in the <olink /> element to the "named destination" for the PDF page |
| --> |
| <refsect1 id="specification"><title>Specification</title> |
| <para> |
| <imageobject> |
| <imagedata fileref="pdficon_small1.gif" format="gif" /> |
| </imageobject> |
| |
| <olink uri="convert_T">OpenCL Specification</olink> |
| </para> |
| </refsect1> |
| |
| <!-- ================================ ALSO SEE --> |
| |
| <refsect1 id="seealso"><title>Also see</title> |
| <para> |
| <citerefentry href="scalarDataTypes"><refentrytitle>Scalar Data Types</refentrytitle></citerefentry>, |
| <citerefentry href="vectorDataTypes"><refentrytitle>Vector Data Types</refentrytitle></citerefentry> |
| </para> |
| </refsect1> |
| |
| <!-- ============================== COPYRIGHT --> |
| <!-- Content included from copyright.inc.xsl --> |
| |
| <refsect3 id="Copyright"><title></title> |
| <imageobject> |
| <imagedata fileref="KhronosLogo.jpg" format="jpg" /> |
| </imageobject> |
| <para /> |
| </refsect3> |
| |
| <!-- 27-Oct-2015, API ver 2.1 rev. 19; C lang 2.0 rev 30 --> |
| </refentry> |
| |
