open TELEMAC-MASCARET The mathematically superior suite of solvers

hi everyone


I'm simulating a channel are sisyphe and I find the following error:

" @STREAMLINE::SCARACT: THE NUMBER OF TRACEBACK INTERFACE CROSSINGS IGEN > 99

PLANTE: PROGRAM STOPPED AFTER AN ERROR
RETURNING EXIT CODE: "

For the simulation I am using paralell with 28 processors with default fortran file.

Find a previous topic that talked about this error and said that there could be a large courant but the number of courant maximum in the last iteration I get 0.39.

I find this strange, because the same run I did using 59 processors and I had no problem.

Hope someone can help me

Joaquin

Hello Joaquin

This error is seen mostly when user introduces large time steps. This means that the traceback algorithm which researches for the Characteristics foot found a path with more than 99 elements, which could happen: either with large time steps or (especially in parallel cases) that the path (which is crossing several subdomain) can be randomly affected by the domain decomposition.
This latter case is a numerical issue which could be assimilated to a "non-reproducible" result or a "cpu-dependant result".
The serial result should be the most trustful, then you should observe the difference between this result and the ones given by parallel runs.


Kind regards

Riadh

hi everyone,

I have the same issue for my simulation, using 26 processors and a lag time of 0.15 s.

I did not check courant number, but if someone could help me to solve this problem...

Should I use a restart file to continue my computation, or use a variable time step?

I attached my listing and cas files.










Regards,

Nicolas

Hi,

I checked Courant number and I have a value of 12 due to topographic errors. I corrected them and I will see.

I also tested by modifiyng my cas file replacing supg option from 2;2 to 1;1.

It works,but can this change impact the accuracy of the results?

Regards,

Nicolas

Dear members,

I was wondering if they help me so I was running TELEMAC-2D but I have this message :
" @STREAMLINE::SCARACT: THE NUMBER OF TRACEBACK INTERFACE CROSSINGS IGEN > 99

In the file cas the time step is 0.01 also y used 20 processor to running.
This message is strange because in the running was stoped at 2 minutes.

Kind regards,

Hi
Sounds like an instability problem near a boundary between 2 subdomains...
It need to be investigate in detail to find the reason...
Save all time step and look at the result to try to find the area where the problem is...
If it's very local, it's possible to run the computation with another number of partition...

Regards