[Kratos] Kratos compilation with gcc AND OPENMP

Riccardo Rossi rrossi en cimne.upc.edu
Mar Nov 9 11:34:54 CET 2010


Dear List,
     this is a sort of preliminary announcement:

i did some benchmarks and arrived to the conclusion that the auxiliary
workspace we use inside elements DOES NOT provide any performance
benefit.

     Since it prevents compilation with compilers other than OpenMP, 
i removed all of the threadprivates from the 
convection_diffusion_application
and
incompressible_fluid_application

those two applicatins, and the external_solvers_app can now compile with
gcc activating the -fopenmp flag.

Surprisingly...performance is now much better with parallel gcc than
with intel!!

I believe that, aside for rough performance, it is a very important
conclusion, since by removing all of the threadprivates, and all of the
static variables in the code we can downgrade our needs from
OpenMP 3.0 to OpenMP 2.5. This will greatly improve portability AND will
allow compiling a parallel application under windows. 

There is still some work to be done in removing threadprivates from the
structural application, i will have a look at that and eventually ask
for help.

A little problem that still exists is related to a known issue:

on "some" linux systems it is necessary to do
export LD_PRELOAD=libstdc++.so.6

prior to launching the examples.

the issue is described here:

http://stackoverflow.com/questions/2778193/segfault-during-cxa-allocate-exception-in-swig-wrapped-library

or in many other posts on the internet.

to compile one should modify the Jamroot so to include -fopenmp in the
gcc flags and also include the libgomp.
See the changes in the Common_Jamroot.

ciao all
Riccardo



-- 
________________________________________________________________
Riccardo Rossi, Ph.D, Civil Engineer
member of the Kratos Group: kratos.cimne.upc.es
Centro Internacional de Métodos Numéricos en Ingeniería (CIMNE)
Universidad Politécnica de Cataluña (UPC)
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08034 Barcelona, España
Tel. (+34) 93 401 73 99
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