[Fwd: [FIELDTRIP] operations on single precision numbers unstable in matlab 7.1 (64bit ) vesions and higher]

[Tom Holroyd (NIH/NIMH) [E]]

Just FYI & amusing.

This was posted on the mailing list of a specialized matlab toolbox:
Hard to see how this could fail. Matlab probably wasn't installed properly
on this 64 bit box.

-------- Original Message --------
Subject: [FIELDTRIP] operations on single precision numbers unstable in  matlab 
7.1 (64bit ) vesions and higher
Date: Tue, 28 Nov 2006 13:55:05 +0100
From: Ali Mazaheri <address@hidden>
Reply-To: FieldTrip discussion list <address@hidden>
To: address@hidden
References: <address@hidden>

Dear all,
The long subject captions says it all.
I just recently discovered that solutions to the  low level functions in 
matlab7.1 and  higher run on a 64 bit platform  become unstable when 
using single precision.
This problem does not appear to be  present on matlabs running on a 32 
bit platform.

.
A simple example of this problem is as follows

a=[1 2]
b=[1 2];

> > a/b
ans = 1

NOW in single precision

a=single(a);
b=single(b);
> > a/b
ans = 1.9074 e-05


the problem of course become much more compounded when doing more higher 
level functions such as detrend. I am completely unable to do a linear 
detrend on
single precious data.


regards
Ali