[Pw_forum] MPI & disk unavailability

[Axel Kohlmeyer]

KK> > locally. The "local" disk may be (and most often is) a networked  
KK> > filesystem; but again, this is handled by the operating system, and  
KK> > completely transparent to Espresso.
KK> 
KK>  OK. But here is my interpretation. Suppose cpu0 wants to write
KK> everything to the NFS disk, which is not there. Then, should not this
KK> write hang and wait till the disk become available? This is not really

for this to work, you first need to configure NFS for reliable 
communication by using hard mounts, that do not timeout easily.

KK> far fetched, such a behaviour easily happens for serial executables.
KK> 
KK>  Now, if cpu0 indeed hangs, but other MPI cpus do not get any answers
KK> within the timeout frame, they start to quit because cpu0 is not
KK> responding.

this handled by the MPI _implementation_. you may want to try a 
different package (there are several others besides MPICH which is 
IMNSHO somewhat clunky , see e.g.: 
http://www.lam-mpi.org/mpi/implementations/shortlist.php ),
or hack your local installation to increase the delay before 
there is a timeout and the library considers the cpu0 process
as dead.

axel.

KK> 
KK>  Any ideas?
KK> 
KK>  Kostya
KK> 
KK>   
KK> 
KK> 
KK> 
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-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
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If you make something idiot-proof, the universe creates a better idiot.