Floating-point software assist fault?

From: "Ed L(dot)" <pgsql(at)bluepolka(dot)net>
To: pgsql-general(at)postgresql(dot)org
Subject: Floating-point software assist fault?
Date: 2008-08-07 23:43:14
Message-ID: 200808071743.14905.pgsql@bluepolka.net
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We're seeing gobs of these via dmesg in PostgreSQL 8.3.3 on
ia64-unknown-linux-gnu, compiled by GCC gcc (GCC) 3.4.6 20060404
(Red Hat 3.4.6-8), kernel 2.6.9-55.EL:

postmaster(13144): floating-point assist fault at ip
40000000003a9382, isr 0000040000000008

It appears to be an Itanium-specific issue with floating-point
normalization, here is a document describing the issue.

http://i-cluster2.inrialpes.fr/doc/misc/fpswa.txt

“The Intel Itanium does not fully support IEEE denormals and
requires software assistance to handle them. Without further
informations, the ia64 GNU/Linux kernel triggers a fault when
denormals are computed. This is the "floating-point software
assist" fault (FPSWA) in the kernel messages. It is the user's
task to clearly design his program to prevent such cases.”

“To conclude, I'd like to stress the fact that the programmer has
to be careful when dealing with floating-point numbers. Even
with high precision, it is easy to produce denormals and get
strange behaviour.”

Any thoughts?

TIA.

Ed

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