[CPMD-list] ibm-sp4

[Alessandro Curioni]

Han -

which type  of    power4 nodes are you using ?  it is a switched machine or
a single SMP node ? How many processors you intend to use ?

I am asking because it make no sense to compile in mixed mode if you intend
to run on lets say on less than 32 processors - use the MPI only
scheme instead ( IBM-SP4) - it will be almost always faster.

If you compile the code using the mixed mode (IBM-SP4-SMP)  you need  to
specify  the number of SMP threads per MPI exporting the variable
XLSMPOPTS=parthds=n - if you don't do this  the program will set it to the
number of CPU available in the node also if you are  already  using this
resources
via MPI tasks. This will saturate the machine with context swiching -  and
terribly slowdown the calculation.

To be more clear if you have an 8 processor node  : you can  run with  8
MPI task and 1 SMP thread (MP_PROCS=8 , XLSMPOTPS=parthds=1) or any other
mixing,
obeying the rule that : Number of MPI task per node * number of SMP threads
= number of processors per node. ( this correspond to a safe use).


Best Regards,

Alessandro


Alessandro CURIONI, PhD
Research Staff Member
Computational Biochemistry and Material Science group
IBM Research Division - Zurich Research Laboratory
Saumerstrasse 4
8003 Rueschlikon - Switzerland
e-mail: cur at zurich.ibm.com
www:    www.zurich.ibm.com
Tel: +41-1-7248633
Fax: +41-1-7248958



                                                                           
             "Wone Keun Han"                                               
             <wkhan at wow.hongik                                             
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                                       [CPMD-list] ibm-sp4                 
             12/15/2004 04:05                                              
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HI all,

I finally installed cpmd on a linux pc without intel math kernel library.
IMKL still gives me trouble to link.

Anyway, I test using  a input file in CPMD-test/femd.
It took about 30 min to finish.

Then I tried run on IBM-SP4.
I compiled cpmd using IBM-SP4-SMP.
It takes more than 4 hours to finish.

Who can give me an idea how to use IBM-SP4?

Thank you,


Wone Keun Han
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