From: Szabolcs Nagy <nsz@port70.net>
To: musl@lists.openwall.com
Subject: [musl] [PATCH] math: fix fma(x,y,0) when x*y rounds to -0
Date: Thu, 14 Mar 2024 00:57:15 +0100 [thread overview]
Message-ID: <20240313235715.GI1884416@port70.net> (raw)
if x!=0, y!=0, z==0 then
fma(x,y,z) == x*y
in all rounding modes, while adding z can ruin the sign of 0 if x*y
rounds to -0.
---
src/math/fma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/math/fma.c b/src/math/fma.c
index 0c6f90c9..adfadca8 100644
--- a/src/math/fma.c
+++ b/src/math/fma.c
@@ -53,7 +53,7 @@ double fma(double x, double y, double z)
return x*y + z;
if (nz.e >= ZEROINFNAN) {
if (nz.e > ZEROINFNAN) /* z==0 */
- return x*y + z;
+ return x*y;
return z;
}
--
2.43.0
reply other threads:[~2024-03-13 23:57 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240313235715.GI1884416@port70.net \
--to=nsz@port70.net \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).