Hello,
I am observing something I have not seen before: a massive loss of precision
with one compiler (out of 3). I have some calculations which have certain
mathematical properties, such as the norm of a quaternion being preserved at
1. With two compilers this is correct within numerical (double) precision,
1E-15 or alike. But with one compiler I am getting much larger discrepancies,
order 1E-13 to 1E-12, and these eventually lead to my whole simulation
breaking down. The calculations involved are many small matrix operations
(inverses, multiplications), so it is quite imaginable there would be
significant roundoff.
What could this be related to? Is it optimization, possible mismatch between
compiler and platform (the compiler is older then the processor), or should I
be checking my codes?
Any hints from people who have experienced this would help.
Thanks,
Aleksandar
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Aleksandar Donev
Complex Materials Theory Group (http://cherrypit.princeton.edu/)
Princeton Materials Institute &
Program in Applied and Computational Mathematics
@ Princeton University
Address:
419 Bowen Hall, 70 Prospect Avenue
Princeton University
Princeton, NJ 08540-5211
E-mail: [log in to unmask]
WWW: http://atom.princeton.edu/donev
Phone: (609) 258-2775
Fax: (609) 258-1177
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