[Nek5000-users] Reading rea file on IBM Blue Gene/Q server

[nek5000-users at lists.mcs.anl.gov]

For performance use .re2 and the latest master available on GitHub.

On 16 May 2017, at 11:57, "nek5000-users at lists.mcs.anl.gov <mailto:nek5000-users at lists.mcs.anl.gov> " <nek5000-users at lists.mcs.anl.gov <mailto:nek5000-users at lists.mcs.anl.gov> > wrote:

Hi Neks,

  We are carrying out an optimization study on IBM Blue Gene/Q server
of IDRIS using direct-adjoint method. The direct and adjoint equations
are solved using Nek5000. We have observed that for moderate to large 
number of
processors  Nek5000 spends considerable time in reading the .rea file.
When we reduce the number of processors, the .rea file is read in lesser 
time but
the time taken for solver increases. To give an idea, a 3D case for 
incompressible flow
with 12000 elements spends 22.132 seconds in reading .rea file if we use
400 processors. If we increase the number of processors to 1000, it 
takes more than
90 seconds to read the same .rea file. Can someone provide us a solution on
how to make Nek read the rea file quickly? Would using .re2 file instead 
of .rea increase
the performance considering the number of elements is not very large.?
I would like to mention that we are using PPLIST="MPIIO" in the makenek 
file.

Many thanks.



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