Opened 6 years ago

Closed 6 years ago

#1039 closed help (fixed)

Different results from new runs and continuation runs

Reported by: eelsj Owned by: willie
Component: UM Model Keywords: Automatic resubmission, NRUN, CRUN
Cc: Platform: HECToR
UM Version: 6.6.3

Description

Hello Helpdesk,

I ran a job (XGTEI) as a new run from 1/1/2020. It ran for 1 month and was restarted as a continuation run for a second month.

I ran another job (XGTEJ) for one month using the restart dumps from XGTEI for ½/2020. The results for February 2020 differ for the two jobs when I was expecting them to be identical.

I have the ancillary reference date defined as 1/12/1978 in both jobs and both jobs are linked to the same pre-compiled code (from job XGTEF).

I have looked through the specification of ancillary files and compared the .leave files but can't see an obvious problem except perhaps the reconfiguration which produces .astart and .ostart files at different dates for the two models. Is this a problem?

Could you tell me how to get the same results from the new and continuation runs, please?

Thank you.

Lawrence

Change History (4)

comment:1 Changed 6 years ago by willie

  • Keywords Automatic resubmission, NRUN, CRUN added
  • Owner changed from um_support to willie
  • Status changed from new to accepted

Hi Lawrence,

The reconfiguration step for xgtej should be switched off. Reconfiguration is only necessary if you are changing grids or adding/updating fields to the start dump -see UMDP S11 for the things reconfiguration can do.

Regards

Willie

comment:2 Changed 6 years ago by grenville

Lawrence

A job run with a given restart file will produce different results as compared with running from the same restart file but reconfigured. However, the model will not give the same answers (even without reconfiguring) under the scenario you describe. An NRUN calls more initialization routines than does a CRUN and hence introduces numerical differences. The model will produce the same answers if an NRUN of the same duration as the combined CRUNS is performed and the dumping frequency is the same for both.

Grenville

comment:3 Changed 6 years ago by eelsj

Grenville

I turned-off the reconfiguration and obtained the same results from my NRUN and CRUN. I was aware of the need for run lengths and dump frequencies to be the same so set my dump frequency at monthly and the run length at one month for both the CRUN and the NRUN.

It think my problem is resolved. Thank you for the help.

Lawrence

comment:4 Changed 6 years ago by grenville

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