[Pw_forum] cp.x and lemieux TRU64 Alpha

[Yonas Abraham]

Hi Paolo,
It looks like the 'bug' is machine dependent. we took
the same input parameter identical source code and run
it in PGI compiler both 32 and 64 bit versions and
intel on 32 bit machines and worked just fine. even
though small perturbation in the machine accuracy
difference can create instability, i would expect the
difference would be bigger between 32 and 64 bits. 
here is the snapshot of the otho diff.

 diff=    2.58117779926850       iter=            1
 diff=    6.73012657805981       iter=            2
  ......///....
 diff=   5.958041775915444E+117  iter=           10
 diff=   1.644433412630960E+235  iter=           11

then it crushes.

we have tried different dt values and didn't help.

any help would be appreciated


--- Paolo Giannozzi <giannozz at nest.sns.it> wrote:

> On Tuesday 26 October 2004 14:54,
> aaron at nemo.physics.ncsu.edu wrote:
> 
> > We have isolated the failure to the subroutine
> ortho
> 
> does the failure occur in one of the first steps
> after a 
> restart? the iterative orthonormalization is
> notoriously 
> unstable if psi(t+dt) and psi(t) differ too much.
> Try to
> reduce the time step, maybe just for the first few
> steps.
> 
> Paolo
> 
> -- 
> Paolo Giannozzi             e-mail: 
> giannozz at nest.sns.it
> Scuola Normale Superiore    Phone:   +39/050-509876,
> Fax:-563513 
> Piazza dei Cavalieri 7      I-56126 Pisa, Italy
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