| .\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de) |
| .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk |
| .\" <mtk.manpages@gmail.com> |
| .\" |
| .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE) |
| .\" Distributed under GPL |
| .\" %%%LICENSE_END |
| .\" |
| .\" Modified 2004-11-15, Added further text on FLT_ROUNDS |
| .\" as suggested by AEB and Fabian Kreutz |
| .\" |
| .TH FMA 3 2017-09-15 "" "Linux Programmer's Manual" |
| .SH NAME |
| fma, fmaf, fmal \- floating-point multiply and add |
| .SH SYNOPSIS |
| .nf |
| .B #include <math.h> |
| .PP |
| .BI "double fma(double " x ", double " y ", double " z ); |
| .BI "float fmaf(float " x ", float " y ", float " z ); |
| .BI "long double fmal(long double " x ", long double " y ", long double " z ); |
| .fi |
| .PP |
| Link with \fI\-lm\fP. |
| .PP |
| .in -4n |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .in |
| .PP |
| .ad l |
| .BR fma (), |
| .BR fmaf (), |
| .BR fmal (): |
| .RS 4 |
| _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L |
| .RE |
| .ad |
| .SH DESCRIPTION |
| These functions compute |
| .IR x " * " y " + " z . |
| The result is rounded as one ternary operation according to the |
| current rounding mode (see |
| .BR fenv (3)). |
| .SH RETURN VALUE |
| These functions return the value of |
| .IR x " * " y " + " z , |
| rounded as one ternary operation. |
| .PP |
| If |
| .I x |
| or |
| .I y |
| is a NaN, a NaN is returned. |
| .PP |
| If |
| .I x |
| times |
| .I y |
| is an exact infinity, and |
| .I z |
| is an infinity with the opposite sign, |
| a domain error occurs, |
| and a NaN is returned. |
| .PP |
| .\" POSIX.1-2008 allows some possible differences for the following two |
| .\" domain error cases, but on Linux they are treated the same (AFAICS). |
| .\" Nevertheless, we'll mirror POSIX.1 and describe the two cases |
| .\" separately. |
| If one of |
| .I x |
| or |
| .I y |
| is an infinity, the other is 0, and |
| .I z |
| is not a NaN, |
| a domain error occurs, and |
| a NaN is returned. |
| .\" POSIX.1 says that a NaN or an implementation-defined value shall |
| .\" be returned for this case. |
| .PP |
| If one of |
| .I x |
| or |
| .I y |
| is an infinity, and the other is 0, and |
| .I z |
| is a NaN, |
| .\" POSIX.1 makes the domain error optional for this case. |
| a domain error occurs, and |
| a NaN is returned. |
| .PP |
| If |
| .I x |
| times |
| .I y |
| is not an infinity times zero (or vice versa), and |
| .I z |
| is a NaN, |
| a NaN is returned. |
| .PP |
| If the result overflows, |
| a range error occurs, and |
| an infinity with the correct sign is returned. |
| .PP |
| If the result underflows, |
| a range error occurs, and |
| a signed 0 is returned. |
| .SH ERRORS |
| See |
| .BR math_error (7) |
| for information on how to determine whether an error has occurred |
| when calling these functions. |
| .PP |
| The following errors can occur: |
| .TP |
| Domain error: \fIx\fP * \fIy\fP + \fIz\fP, \ |
| or \fIx\fP * \fIy\fP is invalid and \fIz\fP is not a NaN |
| .\" .I errno |
| .\" is set to |
| .\" .BR EDOM . |
| An invalid floating-point exception |
| .RB ( FE_INVALID ) |
| is raised. |
| .TP |
| Range error: result overflow |
| .\" .I errno |
| .\" is set to |
| .\" .BR ERANGE . |
| An overflow floating-point exception |
| .RB ( FE_OVERFLOW ) |
| is raised. |
| .TP |
| Range error: result underflow |
| .\" .I errno |
| .\" is set to |
| .\" .BR ERANGE . |
| An underflow floating-point exception |
| .RB ( FE_UNDERFLOW ) |
| is raised. |
| .PP |
| These functions do not set |
| .IR errno . |
| .\" FIXME . Is it intentional that these functions do not set errno? |
| .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6801 |
| .SH VERSIONS |
| These functions first appeared in glibc in version 2.1. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .TS |
| allbox; |
| lbw21 lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR fma (), |
| .BR fmaf (), |
| .BR fmal () |
| T} Thread safety MT-Safe |
| .TE |
| .SH CONFORMING TO |
| C99, POSIX.1-2001, POSIX.1-2008. |
| .SH SEE ALSO |
| .BR remainder (3), |
| .BR remquo (3) |