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57 lines
1.4 KiB
C
57 lines
1.4 KiB
C
/*
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FUNCTION
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<<fma>>, <<fmaf>>---floating multiply add
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INDEX
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fma
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INDEX
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fmaf
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ANSI_SYNOPSIS
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#include <math.h>
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double fma(double <[x]>, double <[y]>, double <[z]>);
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float fmaf(float <[x]>, float <[y]>, float <[z]>);
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DESCRIPTION
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The <<fma>> functions compute (<[x]> * <[y]>) + <[z]>, rounded as one ternary
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operation: they compute the value (as if) to infinite precision and round once
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to the result format, according to the rounding mode characterized by the value
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of FLT_ROUNDS. That is, they are supposed to do this: see below.
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RETURNS
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The <<fma>> functions return (<[x]> * <[y]>) + <[z]>, rounded as one ternary
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operation.
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BUGS
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This implementation does not provide the function that it should, purely
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returning "(<[x]> * <[y]>) + <[z]>;" with no attempt at all to provide the
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simulated infinite precision intermediates which are required. DO NOT USE THEM.
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If double has enough more precision than float, then <<fmaf>> should provide
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the expected numeric results, as it does use double for the calculation. But
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since this is not the case for all platforms, this manual cannot determine
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if it is so for your case.
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PORTABILITY
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ANSI C, POSIX.
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*/
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#include "fdlibm.h"
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#ifndef _DOUBLE_IS_32BITS
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#ifdef __STDC__
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double fma(double x, double y, double z)
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#else
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double fma(x,y)
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double x;
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double y;
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double z;
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#endif
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{
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/* Implementation defined. */
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return (x * y) + z;
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}
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#endif /* _DOUBLE_IS_32BITS */
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