*** PETSC Solver failed to converge *** in parallel mode (TOUOGH3_v1.12- EOS1)

Hi,

I have a problem with code parallelization. The code runs smoothly on my laptop, but as soon as I move to the HPC and use multiple processors, it says *** PETSC Solver failed to converge ***. Due to this, the time step in the simulation does not increase, and the simulation time progresses very slowly (I am planning to simulate around 20 years).

I am using EOS1 (not anticipating the phase change) and have one source term element (defined flow rate and inlet temperature) and another sink element (defined flow rate, with temperature as the variable of interest). On my laptop with the serial model, the time steps are large, but the simulation is slow due to single-core usage. In contrast, on the HPC, the time step barely exceeds 500 s.

When switching from a single-core to a multi-core solver, I modify the INFILE with SOLVR(MATSLV) = 8 and include the .petscrc file in the working folder, which contains:

-ksp_type bcgs  
-pc_type bjacobi  
-ksp_rtol 1e-5  
-ksp_max_it 1000  
-ksp_monitor

I have tried adjusting the max_it and rtol values as well, but without success. Any feedback would be appreciated.