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#1163 (Using land suppression can give different results) – NEMO

Opened 11 years ago

Closed 7 years ago

#1163 closed Bug (wontfix)

Using land suppression can give different results

Reported by: charris Owned by: nemo
Priority: low Milestone:
Component: OCE Version: v3.4
Severity: Keywords:
Cc:

Description

At least for ORCA025, turning on land suppression gives different results on some decompositions (for example 32x30). Is this to be expected? It seems like undesirable behaviour.

Commit History (0)

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Change History (8)

comment:1 Changed 11 years ago by smasson

it is not really expected... :-)
Do you still have the problem if you remove the sea-ice (usually problems comes from this tricky part...)?

comment:2 Changed 11 years ago by charris

I was running without CICE or LIM (just with nn_ice=0) so it wasn't coming from the sea-ice. The differences seemed to be small but I didn't have time to investigate where they were originating.

comment:3 Changed 11 years ago by dupontf

Without changing the MPI tile definition, i.e. a simple roundoff error change?

comment:4 Changed 11 years ago by charris

The domain decomposition should have been the same in both cases, and I was running with key_mpp_rep so I would have expected to be able to get identical results.

comment:5 Changed 11 years ago by smasson

If you compiled with ifort, did you use the option "-fp-model precise"? Without this magic option, I had different results every time I was running the model (same MPI domain decomposition)...

comment:6 Changed 11 years ago by charris

I was using mpxlf90_r on our Power7. But I can normally get the same results when I change domain decomposition, so I'm fairly sure this issue is somehow related to the land suppression.

comment:7 Changed 11 years ago by charris

As I say these differences are very small. Probably bit level on the first time-step (they take three or four time-steps to show up as differences in solver.stat) but I've not investigated in detail.

Has anyone else ever checked that you get the same results with land suppression?

comment:8 Changed 7 years ago by clevy

  • Resolution set to wontfix
  • Status changed from new to closed
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