Re: The disturbing myth of Eiffel portability

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Graham asks

"I'm going out on a wing here, but do Crays use IEEE?  Crays have a long
and established tradition of going their own separate ways on many things
(_Computer Organization and Design_ by Patterson and Hennessy mentions
the ... amusing ability of a Cray to generate a floating-point overflow
when computing z/x if x is very small but not zero).  And nobody's going
to claim you don't use Crays for serious work.

If Java fails to work on Crays, it makes my day ;)"

The old style vector machine Crays (to which P&H refers) definitely are
NOT IEEE, or even close, and as per my previous message use reciprocal
hardware for division, meaning that division results can be off by one bit.
Implementing Java efficiently on those machines, which are now largely
obsolete, is out of the question.

Newer Crays are multiprocessors using at the moment Alpha's, although
considering the ownership, one might expect them to shift to MIPS chips
in the future. But in either case, we are talking about chips that are
subtly IEEE incompatible, as per my previous message.

P.S. for another source of amusing war stories on bogus floating-point
implementations, and an easy introduction to IEEE arithmetic aimed at
software folks rather than hardware folks, see chapter 5 of my book
on Microprocessors (Microprocessors: A Programmer's View, McGraw Hill,
1990, Dewar & Smosna).