Matlab compilation inconsistancies

Hi, im having a strange problem where if i run my matlab script on my home computer, it seems to work fine, but if run on a different computer, the program executes differently. does anybody know what could be wrong?

if it makes any difference, it is for an image classification program where the program accepts an input image and compares it with some images that are stored in the program.

edit: im comparing the workspace variables on two computers, and the difference seems to occur when i call the eig() (eigenvalue and eigenvector) function. Both computers are running Matlab R2010b.

[Image Analyst]

Now how could somebody possibly know what's wrong, given what you have given us to work with?

Answer 1

[Walter Roberson]

Do the two computers have exactly the same processors? If not then it would be normal for their computations to be slightly different. The highly-optimized BLAS libraries might use different internal routines for two different processors, such as if one had a different amount of primary cache than the other did.

Answer 2

[aaa]

no they do not have the same processor. but doesn't that seem very strange? it would be highly improbable for different people to have exactly the same processors all over the world.

[Walter Roberson]

Not so improbable; there are only a relatively small number of "leading contenders" and MATLAB is only supported on x86 and x86_64 architectures which reduces it down to Intel and AMD.

There are strong reasons why one should not expect two different systems to give you the exact same numeric results, especially for calculations such as eig(). I know I have written up a description of the reasons before, but I do not seem to locate it at the moment.