slow 2D tidal simulation

[d.kobashi]

Hi,

I wonder if someone has encountered slow 2D tidal simulation than 3D one. I set up 2D tidal simulation (tide only no wind, no density change) by turning off #undef SOLVE3D, N=1, NDTFAST=1 and DT=0.5 in ocean.in. The model ran successfully, but it was really slow, even noticeably slower than a 3D one (same grid and configuration, but with N=10). No debug mode. I was expecting a 2D run much faster than a 3D run because it has only 1 vertical layer.

Any ideas why? I attach .h, .in and compiler file .mk for your reference.

I ran the model with Intel fortran and MPICH. COAWST version 3.8 (ROMS v3.9?) I downloaded recently.

Thanks in advance.

Bests,

DJ