[Numpy-discussion] Question: why is this different?
meng at are.berkeley.edu
meng at are.berkeley.edu
Mon Oct 17 14:12:23 CDT 2005
Hi there-
I have a question on how this difference arises when I run the following
simple code on windows and Debian:
>>> from numarray import *
>>> a=reshape(arange(81.0), (9,9))+identity(9)
>>> ca = matrixmultiply(transpose(a),a)
>>> import numarray.linear_algebra as la
>>> ica = la.inverse(ca)
>>> ica.min()
-0.30951621414374736
>>> ica.max()
0.8888918586585135
The above is the result in Debian and below is that in Windows:
>>> ica.min()
-0.30951621414449404
>>> ica.max()
0.88889185865875686
So, what caused this difference (both machines have python2.4 and numarray
1.3.2)? The difference happens in the 10th/11th decimal point, which should
be still in the floating point precision, right? This simple difference
caused big differences in my later calculation.
Best,
Xiangyi
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