Re: G77 DOUBLE/SINGLE PRECISION PUZZLE

[Toon Moene <toon at moene dot indiv dot nluug dot nl>]

stephen.buckley@excite.com wrote:
> 
> Dear Helpers
> 
> I am using Force2.0.7 which is an IDE for g77 running under MS windows.
> What I was doing...
> I tried an algorithm in a text for solving a partial
> differential equation numerically.
> What happened..
> running the program at work [we have Windows NT 4.0 installed]
> the answer came out right on the nose--the result column gave
> identical numbers to those in the text.
> Thought I'd run same program at home [I have to do a lot of
> work at home too] and the result column came out really crook--
> nothing like the correct solution. Went over the code and
> couldn't see anything wrong. Tried same program on one of my
> children's computers and got the same result.
> Sitting there wondering what to do next when the thought
> occurred to me to try to see what happens for a small t
> increment [pde is in x and t--t from 0.0 to 0.5]. Tried a small
> step and solution looked OK. A little more and it started to
> drift--by time I went to 60 steps [t=0.3] it was getting way off.
> So I thought hang it let's see what happens if I try double
> precision--and guess what--answer came in right on the nose like
> at work.
> My home computer [and my children's] are running windows 98.
> So does NT 4.0 give more precision for g77 than windows 98?
> 
> It's not a serious problem for me as I can work around it by
> using double precision at home but it is a little puzzling.
> 
> Anyone got any thoughts on this??

No, not really ...

Is it an option to send this program to me so that I could try it on Linux
?

Thanks in advance,

-- 
Toon Moene - mailto:toon@moene.indiv.nluug.nl - phoneto: +31 346 214290
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