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  • learn about OpenIFS input and output files.
  • learn some switches to control OpenIFS.
  • learn how to run the model in parallel.
  • learn how to run the acceptability test.


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titleTasks - Examine t21test directory
  1. Make sure you are in the directory:  $PERM/oifs43r3/t21test
  2. List the files in this directory.

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ref_021_0144
This file is reference output for the model tests. The model can be run in 'reference' mode where it checks it is working correctly by comparing some mathematical norms against these files. Reference runs are described in more detail under 'Acceptance testing' below.

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titleTasks - Examine grib files

Use the grib_ls and grib_dump commands to examine the contents of the ICM files.


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titleTasks - Run model

 Run the model:

% ./job

What happens?

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Whenever the model fails, it will produce this traceback (controlled by DR_HOOK=1 in the job file).

Single process test

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titleTasks - Run the model as a single process

 Copy the file namelists to fort.4 and run the model with a single task and single thread by executing the job script:

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% cp namelists fort.4
% ./run.ppn


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ifs.stat is a small file that prints the model steps, time taken for each step and a 'norm' measure. This file can be usually ignored but is useful for debugging.

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titleTasks - Examine model output

Look at the output from the model in the NODE_001.01 file from this successful run. Note the output of the model namelists and the statistics printed at the end. IFS has very comprehensive logging output which is useful for debugging and understanding the model's performance.

Look at the grib output files using the grib commands.

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These next short tests verify the model works correctly with either OpenMP parallel threading, MPI tasks and both and follow on from the serial tests above.

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titleTasks - Enable OpenMP

Edit the file run.ppn and change the line: export NTHREADS=1 to NTHREADS=4

Run ./run.ppn as above.

Do the reported CPU times change?

Use the grib_ls command to look at grib output files - what do you notice?

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to verify the model ran with 4 OpenMP threads.

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titleTasks - Enable MPI

 Edit the file run.ppn and change NTHREADS back to 1.

Change the line: NPROC=1 to NPROC=4.

Also, edit the fort.4 file and change NPROC to 4.

Rerun the job:
     ./run.ppn

Do the reported CPU times change?

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The final step is to check the model is producing the numerical answers within acceptable limits, even if it runs the short tests above without failing. OpenIFS includes code that will compute internal statistical norms and compare against numbers supplied by ECMWF. The file: ref_021_0144 in the t21test directory contains statistical norms computed by the model run at ECMWF.

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titleTask - run acceptance test

 To do the acceptance test, edit the namelists in fort.4 and look for the NAMCT0 namelist:

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&NAMCT0
 LREFOUT=false,
 NSTOP=6,

change the number of timesteps to 72 to run the model for 12 hours (assuming you have not changed the default timestep of 10mins at T21) and set the LREFOUT to TRUE:

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&NAMCT0
 LREFOUT=true,
 NSTOP=72,


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               e.g
               NFP3DFS = 5,
               MFP3DFS = 130, 135, 138, 155,
               would output the temperature (130), vertical velocities (135), relative vorticity (138), divergence (155) on model levels.

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titleTasks - Change model output

 Using the information above, try:

  1. Adjusting the output frequency of the model.
  2. Changing the list of model levels used for output and the output variables.

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