(j3.2006) Liaison to IFIP WG 2.5

Van Snyder van.snyder
Mon Aug 20 22:30:28 EDT 2007


After the London J3/WG5 meeting, I attended a meeting of IFIP WG 2.5
(Numerical Software).  I presented a report "What's new in Fortran
2003."  WG 2.5 asked me to act as a more-or-less official liaison from
their group to J3 and WG5 (their processes are somewhat less formal than
ours).

I think it would be helpful if J3 were to appoint me as official liaison
to IFIP WG 2.5.

IFIP WG 2.5 are very interested in interval arithmetic.  They plan to
send a letter to IEEE to complain that support for interval arithmetic
in 754r is inadequate.

I pointed out that if IEEE committees are anything like ANSI and ISO
standards committees, it is very difficult to get something specific and
significant into a standard unless somebody actually comes to meetings
and writes words for the standard -- especially if those who come
otherwise don't consider themselves experts or enthusiasts for the
proposal.  Ulrich Kulisch (Wolfgang Walter's mentor) has given me a
manuscript of a book (which he has asked me not to circulate in
electronic form) that explains how simple it would be to support
interval arithmetic in hardware, with not many more transistors (est. 1%
more), and only a very small number of gate delays.  Upper and lower
bounds could in principle be computed in parallel, so interval
arithmetic might be almost as fast as point arithmetic if appropriate
hardware were provided.  Doing it in software at the source level, with
Intel 80x86 processors and the Fortran IEEE support, imposes about 100x
(not %) penalty.

Interval arithmetic is very attractive mathematically.  In addition to
pointing out that IEEE is unlikely to move on interval arithmetic
without a champion who actually attends meetings, I pointed out that J3
and WG5 are equally unlikely to move.  If WG 2.5 want interval
arithmetic, either in Fortran or IEEE 754r, an expert(s) needs to come
to both kinds of meetings.

J3 and WG5 should ponder whether interval arithmetic in Fortran is
hopeless even if an expert, willing to work, shows up at our meetings,
and advise me what to tell IFIP WG 2.5.

-- 
Van Snyder                    |  What fraction of Americans believe 
Van.Snyder at jpl.nasa.gov       |  Wrestling is real and NASA is fake?
Any alleged opinions are my own and have not been approved or
disapproved by JPL, CalTech, NASA, the President, or anybody else.



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