Blowup with OpenMP

parallelization
1

Dear CROCO users,

I’m running the test case of RIP.
Using the default cpp setup (undef OPENMP and undef MPI), the codes runs well.
But when I define OPENMP, the codes blow up after a few steps with the identical croco.in.Rip file.
For example, set NPP=2, NSUB_X=1, NSUB_E=NPP, and export OMP_NUM_THREADS=2.
Then I checked the output, the solutions have extremes around the boundary between two tiles.
So I believe the blowup is caused by some parallel bugs.
Could someone please take a look?

Thank you,
Peng

2

Hi Peng,
I just did a test of RIP case with OpenMP (NPP=2 or 4) and had no problem. What computer and compiler are you using? Did you modify jobcomp?

3

Hi Pmarches, thank you for your reply.
I’m using Linux and ifort. I did not modify jobcomp except changing the compiler to ifort. (gfortran also has this blowup issue.) I did a few tests and found that the blowup issue depends on how to divide the subdomains and number of threads. For example, set NPP=2, NSUB_X=1, NSUB_E=NPP, and export OMP_NUM_THREADS=2, the codes blow up. But set NPP=4, NSUB_X=1, NSUB_E=NPP, and export OMP_NUM_THREADS=2, the codes had no problem. I am not sure why this happens.

4

Hi Peng, I don’t see the problem. The RIP case is routinely tested for parallelization (with automatic procedure). I would advise to make sure that your jobcomp, cppdefs.h and param.h are taken from the OCEAN directory. What linux distribution are you on? … Patrick

5

Hi Peng and Pmarches (and everyone),

I encountered a similar problem with OPENMP and gfortran in UBUNTU. Step2d velocity blowed-up between two tiles. When I turned off OPENMP, this blowing-up was gone.

Do you have more clue about this issue? Thank you.
wf

6

Are you using the released version available on CROCO web site or the Git Master version?

7

It was downloaded from CROCO web site https://www.croco-ocean.org/download/croco-project/

8

Hi Pmarches, I also have similar problem. I use ubuntu 18.04 . thank you. Apri