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• have learnt about how OpenIFS is installed and organised,
• have run it at T21 resolution and know how to run it serially (1 process) and in parallel with both MPI & OpenMP,
• know how to use grib tools to look at model output.
  
  

Connecting to the ECMWF HPC Facilities

In this tutorial, and throughout the entire workshop, you will use one of the Cray XC40 computers which are part of the ECMWF's high-performance computing facility (HPCF).

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Instead of using the login nodes of the HPCF we will use an interactive session to ask for computing resources and fast temporary disk. This also allows to run parallel jobs in the terminal window.Type the following command:  The following tasks need to be carried out only once in order to set up the training accounts and the OpenIFS 43r3 model.

The changed command line prompt indicates that we have switched from the login node to a pre/post-processing node.

You can close the interactive session by typing exit which will bring you back to the login node.

On the ECMWF HPCF an interactive session will last for 48 hrs by default, unless the walltime is specified using an additional directive.

OpenIFS directories

In this section we:

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The actions above will ensure that your training account receives required scripts and shell configuration files.

The last command will copy the model binaries and input files to your account for version 43r3.

Instead of using the login nodes of the HPCF we will use an interactive session to ask for computing resources and fast temporary disk. This also allows to run parallel jobs in the terminal window.

Type the following command:

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The oifs-config.ccb.sh file sets a number of Unix shell environment variables which define the type of OpenIFS compiled installation and location of files.

Make sure you type the source command before you run the model otherwise OpenIFS will not run correctly.

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The changed command line prompt indicates that we have switched from the login node to a pre/post-processing node.

  Important:  After completing your work you need to close the interactive session by typing exit which will bring you back to the login node.

On the ECMWF HPCF an interactive session will last for 48 hrs by default, unless the walltime is specified using an additional directive.

OpenIFS directories

In this section we:

• Set the OpenIFS environment
• Examine the OpenIFS installation
  
  

The directory contains a number of text files and directories:

% ls
CHANGES  CITE  COPYING  LICENSE  NOTICE  README  READMEs/  
bin/  examples/  fcm/  make/  python/  src/  t21test/

Directories:

• src - contains all the source code for the model and supporting programs.
• make - contains the build configuration files for the FCM compile command. Object files and executables will be in this directory organised according to the type of build (OIFS_BUILD environment variable).
• t21test - self contained T21 model run for verifying the installation is correct.
• ifsdata - contains additional input files for the model e.g. climatologies. Available as separate tarfiles.

Note:

• OpenIFS has been precompiled on the HPCF.
• All source code has been removed due to licensing restrictions.
• OpenIFS builds 'out-of-source'; this means object (.o) files and executables (binary files) are not mixed with the source code.
• The README file contains information about software requirements, setting up the local compilation environment, and where to get help and support.

OpenIFS T21 test forecasts

In this section of the tutorial, we will run the pre-compiled OpenIFS model on a simple T21 forecast.

You will:

• 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.

The oifs-config.ccb.sh script sets a number of Unix shell environment variables which define the type of OpenIFS compiled installation and location of files. These settings are specific to version 43r3.

If you do not run this setup script (or alternatively include its content in your Unix shell configuration file) then OpenIFS will not run correctly.

For more information on how to configure OpenIFS, please see the OpenIFS website: http://software.ecmwf.int/oifs/.

The directory contains a number of text files and directories:

% ls
bin/     COPYING    LICENSE  oifs-config.ccb.sh  READMEs/
CHANGES  examples/  make/    python/             src/
CITE     fcm/       NOTICE   README              t21test/

Directories:

• src - contains all the source code for the model and supporting programs.
• make - contains the build configuration files for the FCM compile command. Object files and executables will be in this directory organised according to the type of build (OIFS_BUILD environment variable).
• t21test - self contained T21 model run for verifying the installation is correct.
• ifsdata - contains additional input files for the model e.g. climatologies. Available as separate tarfiles.

Note:

• OpenIFS has been precompiled on the HPCF.
• All source code has been removed due to licensing restrictions.
• OpenIFS builds 'out-of-source'; this means object (.o) files and executables (binary files) are not mixed with the source code.
• The README file contains information about software requirements, setting up the local compilation environment, and where to get help and support.
  
  

OpenIFS T21 test forecasts

In this section of the tutorial, we will run the pre-compiled OpenIFS model on a simple T21 forecast.

You will:

• 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.

The directory t21test contains a number of files:

% ls t21test
ICMGGepc8      ICMGGepc8INIUAICMGGepc8INIT   ICMSHepc8INIT  ifsdatajob  namelists
ICMGGepc8INIT  ICMSHepc8    ref_021_0072
ICMGGepc8INIUA   READMEifsdata/         job      ref_021_0144namelists  run.ppn

Files beginning Files beginning with 'ICM'.
These are the input files for this T21 experiment. They are in GRIB format. Do not move them from this directory. OpenIFS expects to find its input files in the same directory as the main executable.

epc8              - this is the Experiment ID. Experiments IDs are used at ECMWF and initial conditions provided by ECMWF will always have an expt id.
ICMGGepc8  - 'GG' indicates these contain gridpoint fields.
ICMSHepc8  - 'SH' indicates these contains spherical harmonic fields.

job
Simple shell Shell script to run the model. Described in more detail below.

run.ppn
Simple shell script which calls job in an interactive shell environment.

ifsdata
Climate data fields used for T21 test integration. You should not move or rename this directory as the model will expect to find the climate files it needs in a directory of this name.

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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.

The model fails. Look in the NODE_001.01 file and find the subroutine traceback. Near the top of the traceback you will find the error messages.

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

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

norms against these files. Reference runs are described in more detail under 'Acceptance testing' below.

The model fails. Look at the standard output (or in the NODE_001.01 file when it is created) and find the subroutine traceback. Near the top of the traceback you will find the error messages.

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

Single process test

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

The model will expect to find a file called fort.4 in the same directory as the executable. This script copies the executable from make/cce-opt/oifs/bin.

If the run works you will see output like:

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  17:09:08 STEP    1 H=   0:10 +CPU=  0.276
           STEP    1 :## EC_MEMINFO    1 ccbppn01     309     206       0     16530     190    16080    1188     35807   61171      0.2   0.0 s/p
  17:09:08 STEP    2 H=   0:20 +CPU=  0.280
           STEP    2 :## EC_MEMINFO    1 ccbppn01     309     206       0     16530     190    16011    1188     35740   61170      0.2   0.0 s/p
  17:09:08 STEP    3 H=   0:30 +CPU=  0.268
           STEP    3 :## EC_MEMINFO    1 ccbppn01     309     206       0     16530     190    16008    1188     35734   61170      0.2   0.0 s/p
  17:09:09 STEP    4 H=   0:40 +CPU=  0.264
           STEP    4 :## EC_MEMINFO    1 ccbppn01     309     206       0     16530     190    15966    1188     35695   61170      0.2   0.0 s/p
  17:09:09 STEP    5 H=   0:50 +CPU=  0.268
           STEP    5 :## EC_MEMINFO    1 ccbppn01     309     206       0     16530     190    16008    1188     35734   61171      0.2   0.0 s/p
  17:09:09 STEP    6 H=   1:00

The model will expect to find a file called fort.4 in the same directory as the executable. This script copies the executable from make/opt/bin.

If the run works you will see output like:

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signal_drhook(SIGSYS=31): New handler installed at 0x4d06cf; old preserved at 0x0
MPL_BUFFER_METHOD:  2           0
   16:03:46 STEP    0 H=   0:00 +CPU=  3.598
   16:03:46 STEP    1 H=   0:10 +CPU=  0.535
   16:03:47 STEP    2 H=   0:20 +CPU=  0.537004
      16:03:48 STEP     STEP    6 :## EC_MEMINFO    1 3ccbppn01 H=   0:30 +CPU= 309  0.537
   16:03:48206 STEP    4 H= 0  0:40 +CPU=  0.527
16530   16:03:49 STEP 190   5 H=16008   0:50 +CPU= 1188  0.526
   16:03:4935734 STEP  61171  6 H=   1:00 +CPU=0.2   0.5300 s/p

This test runs only 6 a small number of timesteps.

Model output

The model writes its output to a several files.

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NUMBER OF THREADS                 42

to verify the model ran with 4 OpenMP threads.

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Look in the NODE_001.01 output file for the line: "NPROC =     4 2"  to verify that two MPI tasks was used.

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The model can also be set to use NPROC=4 and 2 and NTHREADS=4 to 2 to use a total of 4 processes. However, this would require a computer with at least 16 4 cores.

Acceptance testing

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.

&NAMCT0
 LREFOUT=false,
 NSTOP=6,

&NAMCT0
 LREFOUT=true,
 NSTOP=72,

With LREFOUT=true, at the last timestep OpenIFS will read the ref_021_0144 file and produce a new file: res_021_0144 (note the similar filenames!). The contents of the file should be similar to:

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As long as the model reports 'calculations are correct' and the error is less than a few percent then the model is behaving satisfactorily in your compilation and run environment.

How to control model output

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In this example, the model will write 3 separate output files at the first timestep (0hrs), 3hrs and 9hrs and then no more regardless of how long the model runs for.

How to change the output variables and post-processing

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