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| <h3 class="section">1.21 <code>fma</code>, <code>fmaf</code>–floating multiply add</h3> |
| |
| <p><a name="index-fma-53"></a><a name="index-fmaf-54"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <math.h> |
| double fma(double <var>x</var>, double <var>y</var>, double <var>z</var>); |
| float fmaf(float <var>x</var>, float <var>y</var>, float <var>z</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| The <code>fma</code> functions compute (<var>x</var> * <var>y</var>) + <var>z</var>, rounded as one ternary |
| operation: they compute the value (as if) to infinite precision and round once |
| to the result format, according to the rounding mode characterized by the value |
| of FLT_ROUNDS. That is, they are supposed to do this: see below. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| The <code>fma</code> functions return (<var>x</var> * <var>y</var>) + <var>z</var>, rounded as one ternary |
| operation. |
| |
| <p><br> |
| <strong>Bugs</strong><br> |
| This implementation does not provide the function that it should, purely |
| returning "(<var>x</var> * <var>y</var>) + <var>z</var>;" with no attempt at all to provide the |
| simulated infinite precision intermediates which are required. DO NOT USE THEM. |
| |
| <p>If double has enough more precision than float, then <code>fmaf</code> should provide |
| the expected numeric results, as it does use double for the calculation. But |
| since this is not the case for all platforms, this manual cannot determine |
| if it is so for your case. |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| ANSI C, POSIX. |
| |
| <p><br> |
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