From: Alejandro Colomar <alx@kernel.org>
To: Morten Welinder <mwelinder@gmail.com>
Cc: linux-man@vger.kernel.org, libc-help@sourceware.org,
Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Subject: Re: logb() vs floor(log2()) (was: Man page issues: logb, significand, cbrt, log2, log10, exp10)
Date: Tue, 5 Mar 2024 00:23:55 +0100 [thread overview]
Message-ID: <ZeZYDK7YNG7ptETN@debian> (raw)
In-Reply-To: <ZeYKUOKYS7G90SaV@debian>
[-- Attachment #1: Type: text/plain, Size: 1281 bytes --]
Hi Morten,
On Mon, Mar 04, 2024 at 06:52:10PM +0100, Alejandro Colomar wrote:
> > logb:
> > The formula "floor(log2(x))" should be "floor(log2(fabs(x)))". (Or
> > ...abs(...) if it's meant to be math and not C.)
I've applied thge following patch:
commit 1d83ce827aac984a26430b4f6107182f4b076874 (HEAD -> contrib, alx/contrib)
Author: Alejandro Colomar <alx@kernel.org>
Date: Tue Mar 5 00:20:09 2024 +0100
logb.3: logb(x) is floor(log2(fabs(x)))
log2(3) doesn't accept negative input, but it seems logb(3) does accept
it.
Link: <https://lore.kernel.org/linux-man/ZeYKUOKYS7G90SaV@debian/T/#u>
Reported-by: Morten Welinder <mwelinder@gmail.com>
Cc: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
diff --git a/man3/logb.3 b/man3/logb.3
index 7cbb2470a..7a1ad2f4a 100644
--- a/man3/logb.3
+++ b/man3/logb.3
@@ -58,7 +58,7 @@ .SH DESCRIPTION
is 2,
.BI logb( x )
is equal to
-.BI floor(log2( x ))\fR,
+.BI floor(log2(fabs( x )))\f[R],\f[]
except that it is probably faster.
.P
If
I'll push it tomorrow.
Have a lovely night!
Alex
--
<https://www.alejandro-colomar.es/>
Looking for a remote C programming job at the moment.
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]
prev parent reply other threads:[~2024-03-04 23:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CANv4PNkVv_0eLgiSP3L_KfC-eZJaVLZ5AP1AGfD0GNrR5M4Hrg@mail.gmail.com>
2024-03-04 17:52 ` Alejandro Colomar
2024-03-04 18:47 ` logb() vs floor(log2()) Adhemerval Zanella Netto
2024-03-04 22:16 ` Alejandro Colomar
2024-03-04 23:23 ` Alejandro Colomar [this message]
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=ZeZYDK7YNG7ptETN@debian \
--to=alx@kernel.org \
--cc=adhemerval.zanella@linaro.org \
--cc=libc-help@sourceware.org \
--cc=linux-man@vger.kernel.org \
--cc=mwelinder@gmail.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.
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 read-only IMAP folder(s) and NNTP newsgroup(s).