Nemolite2d difference between PSyclone generated and manual Fortran implementation

[sergisiso]

The manual Fortran implementation uses ssha%grid%subdomain%global%[nx|nx] to calculate the loop boundaries of each kernel while PSyclone generated PSy-layer uses ssha%grid%subdomain%internal%[xstop|ystop].

If I print them in a serial execution of 1024x1024, e.g.:

write(*,*) ssha%grid%subdomain%global%nx, ssha%grid%subdomain%internal%xstop
write(*,*) ssha%grid%subdomain%global%ny, ssha%grid%subdomain%internal%ystop

I get:

        1026        1025
        1026        1025

Implying that the manual version is doing an extra row and column of work. But final ua/uv checksums are not affected:

Implementation               ua checksum    uv checksum    time/step
psyclone_generated   gcc cpu 0.52670513E+02 0.57100321E+03 0.32245E+00
nemolite2d           gcc cpu 0.52670513E+02 0.57100321E+03 0.19181E+00

I believe PSyclone does the right thing, but before making the change, @arporter can you confirm that this makes sense? and also has subdomain%global% the expected value or is there something that may be wrong in dl_esm_inf?

[LonelyCat124]

Do you still get the correct results @ further timesteps? I had some errors only showing at ~12k steps.

Also how accurate is the checksum?

[arporter]

@sergisiso I think that's right. global%nx/y should be the the total number of points in the dimension whereas internal%xstop is the upper bound for the internal/simulated points. I would expect the PSyclone version to be correct whereas the manual version is more likely to have (accidentally) got out of sync.

[arporter]

The checksum is I guess a fairly rough and ready guide but in my experience it is sufficient to show when things are right and when they're not. 12K steps is a lot! I never regularly run for that long so can't comment. For a small domain (~100x100) you've pretty much exercised all the physics by about 6K steps (i.e. incoming waves have reached the end and been reflected back).

[arporter]

@sergisiso can we close this one now?