Message-ID:

When speculation has done its worst, two plus two still equals four. -- S. Johnson

devel / comp.lang.fortran / Re: The standard seems to have a bad example value for TINY(0.0)

The standard seems to have a bad example value for TINY(0.0)

<12464eae-b2bb-4454-ac7a-e651d7ef63c5n@googlegroups.com>

https://www.rocksolidbbs.com/devel/article-flat.php?id=2402&group=comp.lang.fortran#2402

copy link Newsgroups: comp.lang.fortran

X-Received: by 2002:a05:600c:354f:b0:39c:78c8:a854 with SMTP id i15-20020a05600c354f00b0039c78c8a854mr12487190wmq.121.1655510727019;
Fri, 17 Jun 2022 17:05:27 -0700 (PDT)
X-Received: by 2002:a81:7557:0:b0:317:6536:d404 with SMTP id
q84-20020a817557000000b003176536d404mr13391790ywc.459.1655510726378; Fri, 17
Jun 2022 17:05:26 -0700 (PDT)
Path: i2pn2.org!i2pn.org!weretis.net!feeder8.news.weretis.net!proxad.net!feeder1-2.proxad.net!209.85.128.87.MISMATCH!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail
Newsgroups: comp.lang.fortran
Date: Fri, 17 Jun 2022 17:05:26 -0700 (PDT)
Injection-Info: google-groups.googlegroups.com; posting-host=12.154.207.45; posting-account=hzJ1nwoAAACS3IxtuAkjIfQoNdylflgH
NNTP-Posting-Host: 12.154.207.45
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <12464eae-b2bb-4454-ac7a-e651d7ef63c5n@googlegroups.com>
Subject: The standard seems to have a bad example value for TINY(0.0)
From: pmklausler@gmail.com (pmk)
Injection-Date: Sat, 18 Jun 2022 00:05:27 +0000
Content-Type: text/plain; charset="UTF-8"

by: pmk - Sat, 18 Jun 2022 00:05 UTC

According to the standard (F'2018: 16.9.191), TINY(0.0) is 2**(-127) for 32-bit IEEE. I think that's off by a factor of 0.5. The smallest normal 32-bit IEEE-754 number is actually 2**(-126).

Every Fortran compiler to which I have access agrees with me and has TINY(0.0) == 2**(-126).

This error, if it is one, may also affect the example results for RANGE().

Re: The standard seems to have a bad example value for TINY(0.0)

<02403cfe-4235-40fb-9eec-a6d1674bb6e4n@googlegroups.com>

copy mid

https://www.rocksolidbbs.com/devel/article-flat.php?id=2404&group=comp.lang.fortran#2404

copy link Newsgroups: comp.lang.fortran

X-Received: by 2002:a05:600c:1e1c:b0:39c:65a1:7c3a with SMTP id ay28-20020a05600c1e1c00b0039c65a17c3amr23496059wmb.6.1655512650151;
Fri, 17 Jun 2022 17:37:30 -0700 (PDT)
X-Received: by 2002:a81:574c:0:b0:317:7c3a:45be with SMTP id
l73-20020a81574c000000b003177c3a45bemr8743901ywb.316.1655512649534; Fri, 17
Jun 2022 17:37:29 -0700 (PDT)
Path: i2pn2.org!i2pn.org!aioe.org!news.mixmin.net!proxad.net!feeder1-2.proxad.net!209.85.128.88.MISMATCH!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail
Newsgroups: comp.lang.fortran
Date: Fri, 17 Jun 2022 17:37:29 -0700 (PDT)
In-Reply-To: <12464eae-b2bb-4454-ac7a-e651d7ef63c5n@googlegroups.com>
Injection-Info: google-groups.googlegroups.com; posting-host=2601:602:9700:4689:21f0:e94d:5477:b57f;
posting-account=gLDX1AkAAAA26M5HM-O3sVMAXdxK9FPA
NNTP-Posting-Host: 2601:602:9700:4689:21f0:e94d:5477:b57f
References: <12464eae-b2bb-4454-ac7a-e651d7ef63c5n@googlegroups.com>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <02403cfe-4235-40fb-9eec-a6d1674bb6e4n@googlegroups.com>
Subject: Re: The standard seems to have a bad example value for TINY(0.0)
From: gah4@u.washington.edu (gah4)
Injection-Date: Sat, 18 Jun 2022 00:37:30 +0000
Content-Type: text/plain; charset="UTF-8"

by: gah4 - Sat, 18 Jun 2022 00:37 UTC

On Friday, June 17, 2022 at 5:05:29 PM UTC-7, pmk wrote:
> According to the standard (F'2018: 16.9.191), TINY(0.0) is 2**(-127) for 32-bit IEEE. I think that's off by a factor of 0.5. The smallest normal 32-bit IEEE-754 number is actually 2**(-126).
> Every Fortran compiler to which I have access agrees with me and has TINY(0.0) == 2**(-126).
> This error, if it is one, may also affect the example results for RANGE().

Smallest significand of 1.0000000000000 and exponent of -126 agrees with you.

Personally, I think denormals were a bad idea. They give a tiny bit more exponent
range, but a lot more work.

Subject	Author
The standard seems to have a bad example value for TINY(0.0)	pmk
Re: The standard seems to have a bad example value for TINY(0.0)	gah4