[Pw_forum] example01 errors;conjugate-gradient algorithm;changing code functionals

Paolo Giannozzi giannozz at nest.sns.it
Wed May 30 19:07:54 CEST 2007

On May 30, 2007, at 13:48 , Helen wrote:

> I've been working a few days on the problem and have found that it  
> occurs when ZGEMM is called in the ccalbec.f90 routine in the PW  
> directory. The routine is called while calculating force_us_k.

notice to everybody: THIS is an error report! what goes wrong and
where, NOT "it doesn't work" ! :-)

Unfortunately this is as useful as "it doesn't work" :-( , because this
kind of error is either
1) a compiler bug, or
2) a library bug, or
3) a well-hidden bug in the fortran code, causing the code to crash in
some part that is completely unrelated to where the error occurs
(the routine "ccalbec" is called in many different places in the code,
even before the place where it crashes, so the problem cannot be there).

While it is hard to rule out 3), it seems to me exceedingly unlikely  
there is a bug in the simple selfconsistent and force calculation, that
shows up only on one specific executable and cannot be reproduced
on any of the many existing installations of Q-E on many different
machines. My opinion is that it is either 1) or 2). A first simple  
test is
to use internal LAPACK instead of MKL.

> error while loading shared libraries: libguide.so: cannot open  
> shared object file: No such file or directory

this is the first item in the Troubleshooting section:
The surest (but not smartest) way to prevent such problems is to
have a copy of MKL on all processors.

Paolo Giannozzi, Democritos and University of Udine, Italy

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