Subject: Fwd: javanumerics: java floating point

From: Ronald F Boisvert <[email-masked]>
Date: Wed, 02 Dec 1998 14:37:14 -0500

Subject: javanumerics: java floating point
Date: Wed, 02 Dec 1998 11:11:22 +0100
From: "Prof. K. Witsch" <[email-masked]>
Organization: Universitaet Duesseldorf, LS fuer Angewandte Math.
To: [email-masked]

first: thanks to those which contribute to javanumerics

my comment on the response to sun's proposal:

my concern is efficiency. I will not use java when loosing a factor of
two without seeing advantages.

fp numbers are not integers. tests on equality (except 0.0) might be
forbidden. the result of such tests are irrelevant. I see no value in
beeing able to predict the last bit in an intermediate result for 1/3.

standard fp error analysis remains valid when using higher accuracy for
some computations, and the results will be more precise in the mean. why
should i want to loose the additional accuracy? i can see no advantage
at all in storing and reloading intermediate results. i teach students
to arrange computations in a way that the compiler has a chance to leave
intermediate results in fp registers or on a fp stack.

on the other hand: fp error analysis breaks down if some parts of the
computation use unpredictable lower precision. therefore i consider
unnormalized numbers in ieee754 as terrible for numerical analysis and
as an item which should be removed as fast as possible. any operations
with these numbers should result in a fp exception.

I would propose more radical changes to sun's proposal. why should one
forget the success of fortran and c for numerical computations?

kristian witsch