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| <title>Explicit conversions with convert_T()</title> |
| <meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /> |
| <meta name="keywords" content="Explicit conversions with convert_T()" /> |
| </head> |
| <body> |
| <div class="refentry"> |
| <a id="id-1"></a> |
| <div class="titlepage"></div> |
| <div xmlns="" class="refnamediv"> |
| <a xmlns="http://www.w3.org/1999/xhtml" id="convert_T"></a> |
| <h1>Explicit conversions with convert_T()</h1> |
| <p> |
| Explicit type conversions using convert_<code xmlns="http://www.w3.org/1999/xhtml" class="varname">T</code>() |
| </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"> |
| convert_<em class="replaceable"><code>destType</code></em>(<em class="replaceable"><code>sourceType</code></em>) |
| <em class="replaceable"><code>destType</code></em> convert_<em class="replaceable"><code>destType</code></em><_sat><<em class="replaceable"><code>roundingMode</code></em>> (<em class="replaceable"><code>sourceType</code></em>) |
| <em class="replaceable"><code>destTypen</code></em> convert_<em class="replaceable"><code>destTypen</code></em><_sat><<em class="replaceable"><code>roundingMode</code></em>> (<em class="replaceable"><code>sourceType</code></em>) |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="description"></a> |
| <h2>Description</h2> |
| <p> |
| Explicit conversions may be performed using the <code class="code">convert_destType(sourceType)</code> |
| suite of functions. These provide a full set of type conversions between |
| supported types (see <a class="citerefentry" href="scalarDataTypes.html"><span class="citerefentry"><span class="refentrytitle">Scalar Data |
| Types</span></span></a>) except for the following types: |
| <span class="type">bool</span>, <span class="type">half</span>, <span class="type">size_t</span>, <span class="type">ptrdiff_t</span>, |
| <span class="type">intptr_t</span>, <span class="type">uintptr_t</span>, and <span class="type">void</span>. |
| </p> |
| <p> |
| The number of elements in the source and destination vectors must match. |
| </p> |
| <p> |
| 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. |
| </p> |
| <p> |
| The full form of the scalar convert function is: |
| </p> |
| <div class="literallayout"> |
| <p> <code class="code"><em class="replaceable"><code>destType</code></em><br /> |
| convert_<em class="replaceable"><code>destType</code></em><_sat><<em class="replaceable"><code>_roundingMode</code></em>>(<em class="replaceable"><code>sourceType</code></em>)</code></p> |
| </div> |
| <p> |
| </p> |
| <p> |
| The full form of the vector convert function is: |
| </p> |
| <div class="literallayout"> |
| <p> <code class="code"><em class="replaceable"><code>destTypen</code></em><br /> |
| convert_<em class="replaceable"><code>destTypen</code></em><_sat><<em class="replaceable"><code>_roundingMode</code></em>>(<em class="replaceable"><code>sourceTypen</code></em>)</code></p> |
| </div> |
| <p> |
| </p> |
| <h4><a id="id-1.5.7"></a>Data Types</h4> |
| <p> |
| Conversions are available for the following scalar types: <span class="type">char</span>, |
| <span class="type">uchar</span>, <span class="type">short</span>, <span class="type">ushort</span>, <span class="type">int</span>, |
| <span class="type">uint</span>, <span class="type">long</span>, <span class="type">ulong</span>, <span class="type">float</span>, 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. |
| </p> |
| <p> |
| 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. |
| </p> |
| <h4><a id="id-1.5.10"></a>Rounding Modes</h4> |
| <p> |
| 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. |
| </p> |
| <p> |
| </p> |
| <div class="informaltable"> |
| <table class="informaltable" border="1"> |
| <colgroup> |
| <col align="left" class="col1" /> |
| <col align="left" class="col2" /> |
| </colgroup> |
| <thead> |
| <tr> |
| <th align="left">Modifier</th> |
| <th align="left">Rounding Mode Description</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td align="left"> |
| <p> |
| <code class="code">_rte</code> |
| </p> |
| </td> |
| <td align="left"> |
| <p>Round to nearest even</p> |
| </td> |
| </tr> |
| <tr> |
| <td align="left"> |
| <p> |
| <code class="code">_rtz</code> |
| </p> |
| </td> |
| <td align="left"> |
| <p>Round towards zero</p> |
| </td> |
| </tr> |
| <tr> |
| <td align="left"> |
| <p> |
| <code class="code">_rtp</code> |
| </p> |
| </td> |
| <td align="left"> |
| <p>Round toward positive infinity</p> |
| </td> |
| </tr> |
| <tr> |
| <td align="left"> |
| <p> |
| <code class="code">_rtn</code> |
| </p> |
| </td> |
| <td align="left"> |
| <p>Round toward negative infinity</p> |
| </td> |
| </tr> |
| <tr> |
| <td align="left"> |
| <p>no modifier specified</p> |
| </td> |
| <td align="left"> |
| <p> |
| Use the default rounding mode for this destination type, |
| <code class="code">_rtz</code> for conversion to integers or the default |
| rounding mode for conversion to floating-point types. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <p> |
| </p> |
| <p> |
| By default, conversions to integer type use the <code class="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 class="code">_rte</code> for floating-point types. |
| </p> |
| <p> |
| 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. |
| </p> |
| <p> |
| </p> |
| <h4><a id="id-1.5.15.1"></a>Out-of-Range Behavior and Saturated Conversions</h4> |
| <p> |
| </p> |
| <p> |
| 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. |
| </p> |
| <p> |
| Conversions to integer type may opt to convert using the optional saturated mode by |
| appending the <code class="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). |
| </p> |
| <p> |
| Conversions to floating-point type shall conform to IEEE-754 rounding rules. The |
| <code class="code">_sat</code> modifier may not be used for conversions to floating-point formats. |
| </p> |
| </div> |
| <div class="refsect1"><a id="notes"></a><h2>Notes</h2> |
| OpenCL provides <code class="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 class="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 class="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. |
| </div> |
| <div class="refsect2"> |
| <a id="example0"></a> |
| <h3> |
| Examples |
| </h3> |
| <p> |
| In the following example, <code class="function">convert_int4</code> converts a |
| <span class="type">uchar4</span> vector <code class="code">u</code> to an <span class="type">int4</span> vector <code class="code">c</code>: |
| </p> |
| <div class="informaltable"> |
| <table class="informaltable" border="0"> |
| <colgroup> |
| <col align="left" class="col1" /> |
| </colgroup> |
| <tbody> |
| <tr> |
| <td align="left"> |
| uchar4 u; |
| int4 c = convert_int4(u); |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <p> |
| In the following example, <code class="function">convert_int</code> converts a float scalar |
| <code class="code">f</code> to an int scalar <code class="code">i</code>: |
| </p> |
| <div class="informaltable"> |
| <table class="informaltable" border="0"> |
| <colgroup> |
| <col align="left" class="col1" /> |
| </colgroup> |
| <tbody> |
| <tr> |
| <td align="left"> |
| float f; |
| int i = convert_int(f); |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="refsect2"> |
| <a id="example1"></a> |
| <h3> |
| </h3> |
| <p> |
| Example: |
| </p> |
| <div class="informaltable"> |
| <table class="informaltable" border="0"> |
| <colgroup> |
| <col align="left" class="col1" /> |
| </colgroup> |
| <tbody> |
| <tr> |
| <td align="left"> |
| 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 ); |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="refsect2"> |
| <a id="example2"></a> |
| <h3> |
| </h3> |
| <p> |
| Example: |
| </p> |
| <div class="informaltable"> |
| <table class="informaltable" border="0"> |
| <colgroup> |
| <col align="left" class="col1" /> |
| </colgroup> |
| <tbody> |
| <tr> |
| <td align="left"> |
| 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 ); |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="refsect2"> |
| <a id="example3"></a> |
| <h3> |
| </h3> |
| <p> |
| Example: |
| </p> |
| <div class="informaltable"> |
| <table class="informaltable" border="0"> |
| <colgroup> |
| <col align="left" class="col1" /> |
| </colgroup> |
| <tbody> |
| <tr> |
| <td align="left"> |
| 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 ); |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="specification"></a> |
| <h2>Specification</h2> |
| <p> |
| <img src="pdficon_small1.gif" /> |
| |
| <a href="https://www.khronos.org/registry/cl/specs/opencl-2.0-openclc.pdf#namedest=convert_T" target="OpenCL Spec">OpenCL Specification</a> |
| </p> |
| </div> |
| <div class="refsect1"> |
| <a id="seealso"></a> |
| <h2>Also see</h2> |
| <p> |
| <a class="citerefentry" href="scalarDataTypes.html"><span class="citerefentry"><span class="refentrytitle">Scalar Data Types</span></span></a>, |
| <a class="citerefentry" href="vectorDataTypes.html"><span class="citerefentry"><span class="refentrytitle">Vector Data Types</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 © 2007-2015 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> |
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| </html> |
