Opened 12 years ago

Closed 12 years ago

Last modified 4 years ago

#340 closed Enhancement (fixed)

supress useless call to histsync

Reported by: smasson Owned by: nemo
Priority: low Milestone:
Component: OCE Version: release-3.0
Severity: Keywords:
Cc: Review:
MP ready?:
Progress:

Description

supress useless call to histsync which may be costly (real cost??)

Commit History (0)

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Change History (6)

comment:1 follow-up: Changed 12 years ago by smasson

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

done, see changeset:1318

comment:2 in reply to: ↑ 1 Changed 12 years ago by dupontf

Salut Sebastien,

The call to histsync is not benign as far as I understand it. It allows the code to dump the frames to the netcdf history files at each nwrite period. Otherwise, they are all dumped at the end of the simulation. The trouble with dumping all the frames at the end of the simulation is that, if the code crashes (or the system), you lose all the previous frames (at least this is my experience on most Linux clusters).

Why do you think it is an unnecessary cost?

Fred.

comment:3 Changed 12 years ago by smasson

By calling histsync you force NetCDF to flush its buffer and write the data to the disk. If you are using several processes this will act like a MPI_barrier and force all processes to access the disk(s) at the same time. I think it is better to let your system free to handle its buffers used for NetCDF.
We should maybe keep it under a debug mode? But this kind of mode if not really well defined in NEMO. This is a part of a more general implementation a clean debug mode in the code.

comment:4 Changed 4 years ago by nicolasmartin

  • Keywords NEMO added

comment:5 Changed 4 years ago by nicolasmartin

  • Milestone NEMO improvements deleted

Milestone NEMO improvements deleted

comment:6 Changed 4 years ago by nicolasmartin

  • Keywords NEMO removed
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