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[Scalapack] [Scalapackers] Question about MPI and Salapack hybrid code.


Hello Ed,
FYI: http://icl.cs.utk.edu/lapack-forum/viewtopic.php?t=136 ,
(some of hte recent post on scalapack@Domain.Removed are pretty old even if 
they just arrived now)
Julien

On Wed, 18 Jan 2006, Eduardo D'Azevedo wrote:


You can try using blacs_get to get the system context (what=10), which
is most likely the mpi communicator.

http://www.netlib.org/blacs/BLACS/QRef.html#BLACS_GET


Ming Li wrote:

Hello, Scalapack developper,

I have question regarding "hybrid" code by combing MPI
and scalapack together. I read the scalapck user
guide, but didnot get related contents. So I seek help
from this E-mail list.


My problem is as following:
-------------------------------
Scalapck is based on pblas and blacs which is a
seperate communciation language different from MPI.
Blacs has it own initializ and close subroutine. So in
scalapck code, there is no explicit MPI and scalapck
will use all the available CPUs as one special CPU and
all the memroy as one memory attached to this special
CPU. I can specify how many CPUs for my scalapck
program (for example: 4, 16 ...).

My question is: can I have the chance to write a code
which use both scalapck and explicit MPI? That is:
specify each 4 CPUs as a group and each group run my
scalapack code and at the same time I use MPI in the
code to assign differeent group of CPUs for scalapack
code.

For example, my code required large memory (i.e. one
matrix is larger than 4GB), I have to use scalapack to
use distribute memory. At the same time my code has a
main loop and in each step of the main loop the
calculation is independent, so I can use MPI very
easily to let it run parallelly.

If I have 16 CPUs available, I can group 4 CPUs a
unit, then I have for set of 4 CPUs. Can I use both
MPI and scalapack to let the my code automatically
assign 4 CPUs for each scalapack code and the scalapck
code is running parallelly on 4 different set of
4-CPUs.
-------------------------------------------

this problem is sound like a "hybrid" parallel
computaion. Anyone has the similar problem to solve
and can give me some suggestion?

Thank you very much!

Ming



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