* Ada Floating-point model
@ 1997-08-12 0:00 Geert Bosch
1997-08-14 0:00 ` Matthew Heaney
0 siblings, 1 reply; 2+ messages in thread
From: Geert Bosch @ 1997-08-12 0:00 UTC (permalink / raw)
I am trying to understand the floating point model of Ada.
Hopefully somebody would like to answer my questions below.
Does a model interval associated with a value of a floating
point type include one or two model numbers?
The RM defines a model interval as an interval whose bounds
are model numbers, but doesn't tell which bounds are included
in the interval.
Then there is a remark that the model interval of a model number
consists of that number only. So when I use two model numbers as
operands of a predefined operation, the result should be in
the smallest model interval containing the result. When this
result is a model number this interval consists of that
number only and the operation is exact, right?
Regards,
Geert
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Ada Floating-point model
1997-08-12 0:00 Ada Floating-point model Geert Bosch
@ 1997-08-14 0:00 ` Matthew Heaney
0 siblings, 0 replies; 2+ messages in thread
From: Matthew Heaney @ 1997-08-14 0:00 UTC (permalink / raw)
In article <5sq0qt$aev$1@gonzo.sun3.iaf.nl>, Geert Bosch
<geert@gonzo.sun3.iaf.nl> wrote:
>I am trying to understand the floating point model of Ada.
>Hopefully somebody would like to answer my questions below.
I can't answer you directly, as this is the very stuff I'm still trying to
learn. But here's at least something. Ada 83 was influenced by the "Brown
model," documented in
A Simple but Realistic Model of Floating-Point Computation
W. S. Brown
ACM Tranactions on Mathematical Software
Vol. 7, No. 4, December 1981, p 445-480
Even today, after many years of Ada programming, I'm still not sure what a
"safe" number is, though I think I understand what a model number is.
--------------------------------------------------------------------
Matthew Heaney
Software Development Consultant
<mailto:matthew_heaney@acm.org>
(818) 985-1271
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