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the information on this page is not complete.

not sure how restarts get enabled, just setting NFRRES/NRESTS doesn't seem to be enough - is there a master switch somewhere?

mention rcf file/namelist

 

What's a model restart?

A restart allows the model to continue a forecast with a succession of  individual runs, each one starting where the other one left off. e.g. running an extended forecast of 100 days with 5 separate runs of 20 days each. A restart will always be exact, that is, the results of the restarted forecast should always match a single run of the model for the same total length (assuming all settings remain the same).

This page describes how to configure and use the model restart facility.

n.b. the restarted run must always have the same parallel decomposition (TASKS x THREADS)

How to configure restarts

The namelist NAMRES controls model restarts (see ifs/namelist/namres.h). The most useful variables in this namelist are: NFFRES and NRESTS.

NFRRES : frequency of restart file writes (restart file interval)

This can be either positive or negative.

If positive it represents a frequency in model timesteps. e.g. NFRRES=144 means a restart file will be created every 144 model timesteps. With a timestep of 10mins this would mean restart files are written every day.

If negative it represents a frequency in hours. e.g. NFRRES=-48, would mean the model creates restart files every 2 days regardless of the model timestep.

NFRRES is ignored if the first entry in the NRESTS array is non-zero.

NRESTS : list of restart times.

Values for NRESTS can be either positive in which case they are interpreted as the model timesteps at which a restart file is made, or negative in which case they specify hours.

Examples

Example 1: Regular output frequency
 &NAMRES
       NFRRES=-24,
 /

In this trivial example, the model will write restart files every 24hrs (as NFRRES is negative). NRESTS does not need to be specified (defaults to zero).

Example 2: Irregular restart frequency in hours
 &NAMRES
       NFRRES=1,
       NRESTS=-3,-48,-120,-192,
 /

In this example, restart files will be created at 3hrs, 48hrs, 120hrs and 192hrs. Note the restart files do not need to be created at equally spacing intervals if using a list of restart times in NRESTS. The value of NFRRES is ignored in this case as the first entry in NRESTS is nonzero.

Files

Restart files

The output files all begin with the name 'srf'. One file will be created per MPI task. The files are written as unformatted binary (not GRIB).

By default, old restart files are automatically deleted. This is advisable because the files can be very large. One restart file at T1279 is approx 500Mb when using 128 MPI tasks, giving a total restart file requirement of approx 64Gb. Changing this behaviour is not possible via NAMRES. Instead, edit the file ifs/setup/sures.F90 and change the default value of LDELRES to TRUE.

Restart namelist

Model code

The key subroutines for restarts are:

monio.F90 - sets up the internal arrays to determine write times

wrresf.F90 - calls the I/O subsystem to write out the model arrays. If you add more arrays to the model and want them to appear in restart files, change this routine.

 

 


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