Re: Machine epsilon, Octave and Matlab

[geraint . p . bevan . itar]

On Wed, 29 Aug 2001, Craig Stoudt wrote:

> Interesting.  I'm running Octave 2.1.31 under Win2000.
>  Running your script I get:
>
> x2 =  1.1102230246251565404e-16
> y2 = 0
> x4 =  5.5511151231257827021e-17
> y4 = 0
>
> I wonder if this was changed in version 2.1.33
>
>
> Craig Stoudt


It looks unlikely that it changed - version 2.0.14 gives the same result
as 2.1.33 on my machine. Perhaps it is a machine and/or operating system
issue - did you run Octave and Matlab on the same machine? Alternatively,
you may be able to change Octave's behaviour by re-compiling it with
different options.


cat << EOF | gnu/octave-2.0.14-mips-sgi-irix6.4/bin/octave
> x2 = eps/2
> y2 = 1/(1-x2) - 1/(1+x2)
> x4 = eps/4
> y4 = 1/(1-x4) - 1/(1+x4)
> EOF


GNU Octave, version 2.0.14 (mips-sgi-irix6.4).
Copyright (C) 1996, 1997, 1998, 1999 John W. Eaton.
This is free software with ABSOLUTELY NO WARRANTY.
For details, type `warranty'.

x2 =  1.1102e-16
y2 =  2.2204e-16
x4 =  5.5511e-17
y4 = 0

-- 
Geraint.



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