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[Scalapack] determinism in pzheevd

Dear Nichols,

Thank you for pointing out this issue.  I believe you are correct that it is 
the BLACS routine BI_TreeComb that is not deterministic and causing the 
irreproducibility you are seeing in PZHEEVD.  I do not know of another version 
that produces consistent results on the same processor configurations.  It is 
possible, however, that we may add this functionality to a future version of 



On Nov 20, 2012, at 11:05 AM, "Nichols A. Romero" <naromero@Domain.Removed> 


Is PZHEEVD deterministic? By that I mean, if I fix the input matrix and run 
PZHEEVD repeatedly on a fixed number of MPI tasks on the same architecture 
will I get the same result to machine precision every time. Let's assume 
everything is single-threaded, e.g. no threaded BLAS.

After some discussion, with a vendor (IBM) and the MPICH2 developers I am 
told that collectives are deterministic. 

After taking a closer look at PZHEEVD, the only non-deterministic behavior I 
see is in the routine PZHETRD which uses BI_TreeComb which itself does not 
look deterministic from the use of MPI_ANY_SOURCE (define to the variable 

Is there a deterministic version of BI_TreeComb available?

Nichols A. Romero, Ph.D.
Argonne Leadership Computing Facility
Argonne National Laboratory
Building 240 Room 2-127
9700 South Cass Avenue
Argonne, IL 60490
(630) 252-3441
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