Path: ...!weretis.net!feeder9.news.weretis.net!i2pn.org!i2pn2.org!.POSTED!not-for-mail
From: mitchalsup@aol.com (MitchAlsup1)
Newsgroups: comp.arch
Subject: Re: Making Lemonade (Floating-point format changes)
Date: Tue, 21 May 2024 22:20:20 +0000
Organization: Rocksolid Light
Message-ID: <ad32edabe852e1be3df40c36ebf00530@www.novabbs.org>
References: <abe04jhkngt2uun1e7ict8vmf1fq8p7rnm@4ax.com> <memo.20240512203459.16164W@jgd.cix.co.uk> <v1rab7$2vt3u$1@dont-email.me> <20240513151647.0000403f@yahoo.com> <v1to2h$3km86$1@dont-email.me> <20240514221659.00001094@yahoo.com> <v234nr$12p27$1@dont-email.me> <20240516001628.00001031@yahoo.com> <v2cn4l$3bpov$1@dont-email.me> <v2d9sv$3fda0$1@dont-email.me> <20240519203403.00003e9b@yahoo.com> <v2etr0$3s9r0$1@dont-email.me> <20240520113045.000050c5@yahoo.com> <v2ff99$3vq7q$1@dont-email.me> <20240520153630.00000b5a@yahoo.com> <v2g7js$4vi9$1@dont-email.me> <20240521104659.00003fa0@yahoo.com> <e6f23396245cccf5a852718d100d044a@www.novabbs.org> <jwva5kj9c0j.fsf-monnier+comp.arch@gnu.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Info: i2pn2.org;
	logging-data="1818114"; mail-complaints-to="usenet@i2pn2.org";
	posting-account="65wTazMNTleAJDh/pRqmKE7ADni/0wesT78+pyiDW8A";
User-Agent: Rocksolid Light
X-Spam-Checker-Version: SpamAssassin 4.0.0
X-Rslight-Posting-User: ac58ceb75ea22753186dae54d967fed894c3dce8
X-Rslight-Site: $2y$10$4XcUfokMUXyJJHQN36bfpu2ntx02wOJkiqaN1RMqSzNy5503zFexK
Bytes: 2608
Lines: 25

Stefan Monnier wrote:

>>> I think, we were discussing multiplication stage of FMA rather than
>>> multiplication proper.
>>> In case of FMA, zeroness (zeroity ?) and sign of tiny product matter in
>>> all standard IEEE rounding mode except default (RNE).
>> Imagine, instead, if IEEE 754 had defined positive underflow with the
>> result of positive tiny, negative underflow with negative tiny,
>> positive overflow with positive infinity-epsilon and negative
>> overflow with negative infinity+epsilon.
>> Here, the fact overflow or underflow happened is recorded in the
>> result, and these results remain identifiable from real infinities
>> or real zeros.
>> But that ship sailed 50 years ago.

> Wouldn't that just kick the problem down the street?
> For example, what should `x < y` return when both `x` and `y` are
> "infinity+epsilon"?

You mean -infinity+epsilon or +infinity-epsilon. +infinity+epsilon
is +infinity ...

IEEE 754 has +infinity == +infinity && -infinity == -infinity


>         Stefan