From a27d2baa0c1a2ec70f47ea9199b1dd6762c8a349 Mon Sep 17 00:00:00 2001 From: The Android Open Source Project Date: Tue, 21 Oct 2008 07:00:00 -0700 Subject: Initial Contribution --- libm/man/fma.3 | 116 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 116 insertions(+) create mode 100644 libm/man/fma.3 (limited to 'libm/man/fma.3') diff --git a/libm/man/fma.3 b/libm/man/fma.3 new file mode 100644 index 0000000..078a6e2 --- /dev/null +++ b/libm/man/fma.3 @@ -0,0 +1,116 @@ +.\" Copyright (c) 2005 David Schultz +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" $FreeBSD: src/lib/msun/man/fma.3,v 1.3 2005/11/24 09:25:10 joel Exp $ +.\" +.Dd January 22, 2005 +.Dt FMA 3 +.Os +.Sh NAME +.Nm fma , +.Nm fmaf , +.Nm fmal +.Nd fused multiply-add +.Sh LIBRARY +.Lb libm +.Sh SYNOPSIS +.In math.h +.Ft double +.Fn fma "double x" "double y" "double z" +.Ft float +.Fn fmaf "float x" "float y" "float z" +.Ft long double +.Fn fmal "long double x" "long double y" "long double z" +.Sh DESCRIPTION +The +.Fn fma , +.Fn fmaf , +and +.Fn fmal +functions return +.No "(x * y) + z" , +computed with only one rounding error. +Using the ordinary multiplication and addition operators, by contrast, +results in two roundings: one for the intermediate product and one for +the final result. +.Pp +For instance, the expression +.No "1.2e100 * 2.0e208 - 1.4e308" +produces \*(If due to overflow in the intermediate product, whereas +.No "fma(1.2e100, 2.0e208, -1.4e308)" +returns approximately 1.0e308. +.Pp +The fused multiply-add operation is often used to improve the +accuracy of calculations such as dot products. +It may also be used to improve performance on machines that implement +it natively. +The macros +.Dv FP_FAST_FMA , +.Dv FP_FAST_FMAF +and +.Dv FP_FAST_FMAL +may be defined in +.In math.h +to indicate that +.Fn fma , +.Fn fmaf , +and +.Fn fmal +(respectively) have comparable or faster speed than a multiply +operation followed by an add operation. +.Sh IMPLEMENTATION NOTES +In general, these routines will behave as one would expect if +.No "x * y + z" +were computed with unbounded precision and range, +then rounded to the precision of the return type. +However, on some platforms, if +.Fa z +is \*(Na, these functions may not raise an exception even +when the computation of +.No "x * y" +would have otherwise generated an invalid exception. +.Sh SEE ALSO +.Xr fenv 3 , +.Xr math 3 +.Sh STANDARDS +The +.Fn fma , +.Fn fmaf , +and +.Fn fmal +functions conform to +.St -isoC-99 . +A fused multiply-add operation with virtually identical +characteristics appears in IEEE draft standard 754R. +.Sh HISTORY +The +.Fn fma +and +.Fn fmaf +routines first appeared in +.Fx 5.4 , +and +.Fn fmal +appeared in +.Fx 6.0 . -- cgit v1.1