[CIG-SEISMO] global_s362ani instability with certian configuration

[Luo, Ping]

Hello,

I obtained the newest development version of SPECFEM3D_GLOBE (not the tar.gz one) and tried to run global_s362ani in the EXAMPLES directory. My intention is to keep the number of elements per core to a constant (48*48) and vary the number of cores. The parameters I set in the Par_file are listed in the table below.

#elements/core = 48*48

NPROC_XI NPROC_ETA  NEX_XI  NEX_ETA   total cores
  2         2         96       96     6*2*2=24   
  4         4         192      192    6*4*4=96
  6         6         288      288    6*6*6=196
  8         8         384      384    6*8*8=384
  10        10        480      480    6*10*10=600


The tests ran to completion except for NPROC 8x8, in which the solver became unstable and blew up. The norm and potential from the timetamp files is listed below. It seems the computation blow up before step 60.

timestamp000005: Max norm displacement vector U in solid in all slices (m) =   1.2461744E-03
timestamp000005: Max non-dimensional potential Ufluid in fluid in all slices =   1.0009440E-24
timestamp000020: Max norm displacement vector U in solid in all slices (m) =   9.6447496E-03
timestamp000020: Max non-dimensional potential Ufluid in fluid in all slices =   1.0034338E-24
timestamp000040: Max norm displacement vector U in solid in all slices (m) =   1.8385876E-02
timestamp000040: Max non-dimensional potential Ufluid in fluid in all slices =   1.0065002E-24
timestamp000060: Max norm displacement vector U in solid in all slices (m) =    154.3319    
timestamp000060: Max non-dimensional potential Ufluid in fluid in all slices =   1.0093262E-24
timestamp000080: Max norm displacement vector U in solid in all slices (m) =   1.6437107E+11
timestamp000080: Max non-dimensional potential Ufluid in fluid in all slices =   1.0125660E-24
timestamp000100: Max norm displacement vector U in solid in all slices (m) =   1.7506350E+20
timestamp000100: Max non-dimensional potential Ufluid in fluid in all slices =   1.0156563E-24
timestamp000120: Max norm displacement vector U in solid in all slices (m) =   1.1403834E+26
timestamp000120: Max non-dimensional potential Ufluid in fluid in all slices =   1.0184948E-24

My questions are: why the 8x8 case crashed, but all other cases worked fine, and how to fix it.


Thanks,

Ping