[CIG-SEISMO] specfem3d_globe-7.0.0 overflow

[Dimitri Komatitsch]

Dear Tsuboi-san,

Thank you very much for your answer.
To change the value of the time step DT automatically computed by the 
code, you can edit file src/shared/get_timestep_and_layers.f90 and put 
something like:

DT = DT * 0.90

at the end of that routine. This should fix the problem.

Best regards,
Dimitri Komatitsch.

On 07/03/2018 06:41 AM, Seiji Tsuboi wrote:
> Dear Komatitsch-san
> 
> Thank you very much for your very quick reply to my inquiry.
> Since I could not find where I should reduce DT in the program, I have 
> turned both USE_LDDRK and INCREASE_CFL_FOR_LDDRK on. Then computation 
> proceeds for NPROC=17 and NEX=816 case without overflow but the time per 
> iteration becomes almost 6 times longer. It may be necessary to compute 
> for more than one day. Is this what we expect? Should I turn USE_LDDRK 
> false and reduce DT instead?
> 
> Best regards,
> Seiji Tsuboi
> 
> 2018-07-03 6:02 GMT+09:00 Dimitri Komatitsch <komatitsch at lma.cnrs-mrs.fr 
> <mailto:komatitsch at lma.cnrs-mrs.fr>>:
> 
> 
>     Dear Tsuboi-san,
> 
>     It is probably the time step computed automatically by the code that
>     is slightly above the CFL stability limit in that case. Thus, you
>     probably just need to reduce the value of variable DT a bit (say 10%
>     or so).
> 
>     Best regards,
>     Dimitri.
> 
>     On 07/02/2018 09:41 AM, Seiji Tsuboi wrote:
> 
>         Dear Sir,
> 
>         I have used specfem3d_globe-7.0.0 on intel cluster and have
>         overflow problems.
>         If I set NPROC=16 and NEX=768 (1536 cores), I could calculate
>         seismograms correctly. However if I increase NEX, for example
>         NPROC=17, NEX=816 (1734 cores), xspecfem3D stops with overflow
>         in the very beginning of computation. ATTENUATION is set as true
>         and it seems that the program overflows in
>         "multiply_accel_elastic" routine. I tried both ifort and
>         gfortran but the situation is the same. I would be grateful if
>         someone would let me know how I should solve this issue.
> 
>         Best regards,
>         Seiji Tsuboi
> 
> 
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> 
>     -- 
>     Dimitri Komatitsch, CNRS Research Director (DR CNRS)
>     Laboratory of Mechanics and Acoustics, Marseille, France
>     http://komatitsch.free.fr
> 
> 

-- 
Dimitri Komatitsch, CNRS Research Director (DR CNRS)
Laboratory of Mechanics and Acoustics, Marseille, France
http://komatitsch.free.fr