Minutes of the QUEST-ESM NCAS FAMOUS meeting of Monday, 1st October 2007
Present: Ros, Jeff, Lois, Robin, Simon, Annette, Jonathan
A new version of FAMOUS is nearly ready. This is still MOSES 1 but includes the science changes Robin has been working on over the last year (sea-ice tuning, ozone, orography, iceberg-substitute flux adjustment) and various technical improvements (very long absolute time convention for filenames, orbital forcing mod). Robin is currently running a control on HPCx. When this is done, Annette will do one on quest, and we will compare statistically as usual. As this is a major release, testing an ensemble (which is statistically more rigorous) would be valuable. If there are no problems, the release will be made, on puma in the FAMOUS-enhanced version of the UMUI. The mods etc. will also be stored on puma, as well as being installed on HPCx and quest. It is appropriate to use puma for sharing UM-related files in this way. The very long absolute time convention requires an option in the UMUI and some of the small executables have to be replaced, because the namelist entries for filenames have to allow for longer strings. This is backward compatible.
Annette has run successfully on the quest cluster, which has now generally been stable for a month or so. There are unclear issues about scripts and commands to submit jobs, and bottlenecks for output. This will become clearer to us when we have more experience with using it, as Robin will soon do.
Simon has carried out some timing tests for FAMOUS on HECToR and quest. He reports that 1×8 PEs in the atmos is about twice as fast as 8×1 on both machines. Such a sensitivity is not usual and must somehow be related to FAMOUS low resolution, as it arises from communications overhead. On HPCx we run on 16 PEs but perhaps there is a similar sensitivity. The fastest Simon obtained on HECToR was 124 years/day on 8 PEs and 138 on 16. He pointed out we are using code options for faster execution but loss of bit-comparability with different PE configurations, and will check the effect of not using these options, as bit-comparability is very desirable.
Coastal tiling for MOSES 2.2 at 4.5 is now technically running. There have been various problems with some fields in the initial dump, related to the unavoidably ad-hoc way it was made and fragile code. At present it runs for about 391 days before crashing with negative pressure (as usual), but this doesn’t seem to be a symptom of the dynamical instability we have had before, as restarting from slightly different dumps does not help. Robin will focus in with more diagnostics.
Jeff has had little time for xancil and is currently occupied with HECToR. In xancil for dumps, replacement of atmos fields nearly works. Replacement of ocean fields will be a similar exercise. Addition of new fields and other useful features for ocean dumps have not yet been addressed.
Oli is routinely running FAMOUS with Glimmer. We will be including this in the finally delivered FAMOUS, with UMUI support, but Jonathan has not looked into possibilities yet. Lois reminded us of the difficulties that Taro encountered with compiling Glimmer.