ScaLAPACK example code execution error

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ScaLAPACK example code execution error

Postby ravi » Tue Apr 19, 2005 2:09 am

i m trying to run an exmple code of scalapack for testing..but i m getting the error .....

the configuration of Pc is 3.6 GHz, 2GB RAM fedora-3 kernal 2.6.9-1.667smp each.....

for compilation of the code as

mpif77 example.f \
/usr/local/include/libscalapack.a \
/usr/local/include/blacsF77init_MPI-LINUX-0.a \
/usr/local/include/blacs_MPI-LINUX-0.a \
/usr/local/include/blacsF77init_MPI-LINUX-0.a \
/usr/local/include/blas_LINUX.a

after this i have given the command for run like
mpirun N a.out
where N=4
the result comes out to be

ScaLAPACK Example Program #1 -- May 1, 1997

Solving Ax=b where A is a 9 by 9 matrix with a block size of 2
Running on 4 processes, where the process grid is 2 by 2

INFO code returned by PDGESV = 8

According to the normalized residual the solution is incorrect.

||A*x - b|| / ( ||x||*||A||*eps*N ) = 4.64139092E+14


what are the reasons for the solution to be incorrect....that is not empasised with the example code....as i m new with this parallelization options...please help me out of this....
tia
ravi :(
ravi
 
Posts: 9
Joined: Wed Apr 13, 2005 7:08 am

Postby Stan Tomov » Tue Apr 26, 2005 7:52 pm

Dear Ravi,
Example 1 that you are trying to run is hard coded for a
process grid of 2 by 3, so you have to request at least 6
processes. For example
Code: Select all
mpirun -np 6 example1

gives
Code: Select all
ScaLAPACK Example Program #1 -- May 1, 1997

Solving Ax=b where A is a   9 by   9 matrix with a block size of   2
Running on   6 processes, where the process grid is   2 by   3

INFO code returned by PDGESV =   0

According to the normalized residual the solution is correct.

||A*x - b|| / ( ||x||*||A||*eps*N ) =   0.00000000E+00


Regards,
Stan
Stan Tomov
 
Posts: 13
Joined: Thu Dec 09, 2004 1:28 pm


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