EMOSLIB to disappear on new HPC in Bologna

[pesei]

​EMOSLIB has been retired by ECMWF and it will ​not be provided on the new HPC system in Bologna, which should become operational around March or April 2022.

Emoslib is used in the Fortran code of flex_extract. It should be checked what exactly is used and necessary changes should be implemented.

[pesei]

Extraction of all entry points in libemosR64.so.0d (Debian package libemos0d) via

nm -D /usr/lib/x86_64-linux-gnu/libemosR64.so.0d | grep T | cut -d\  -f3 | sed "s/_//" > emoslib

and then search the Fortran files in flex_extract_v7.1.2/Source/Fortran/ for all of them. We find:

fft99
grphreal.f90:    CALL FFT99(CXM,WSAVE,TRIGS,IFAX,1,1,MAXL,1,-1)
phgrreal.f90:    CALL FFT99(CXM,WSAVE,TRIGS,IFAX,1,1,MAXL,1,1)

jsppole
calc_etadot.f90: CALL JSPPOLE(XMN(:,K),1,MNAUF,.TRUE.,CUA(:,:,K))
calc_etadot.f90: CALL JSPPOLE(XMN(:,MLEVEL+K),1,MNAUF,.TRUE.,CVA(:,:,K))
calc_etadot.f90: CALL JSPPOLE(XMN(:,K),-1,MNAUF,.TRUE.,CUA(:,3:4,K))
calc_etadot.f90: CALL JSPPOLE(XMN(:,MLEVEL+K),-1,MNAUF,.TRUE.,CVA(:,3:4,K))

set99
calc_etadot.f90: CALL SET99(WSAVE,IFAX,mauf)
calc_etadot.f90: CALL SET99(GWSAVE(1,J),GIFAX(1,J),MLAT(J))

fft99 calculates the FFT, set99 initialises for the FFT, and jsppole calculates some Fourier coefficients.

This code is only executed with the setting GAUSS 1. As ​explained in the documentation, this is required only if using ERA-40, ERA-Interim or operational data prior to September 2008.

Options

1. Very quick fix: Provide do-nothing versions of these three subroutines in order to remove the dependency on EMOSLIB, and disable usage of GAUSS 1. Problem: Few cases where someone need this.

2. Quick fix: Replace the Fortran code by calls to eccodes form a Python programme integrated with the rest of flex_extract. Problem: same as above. Advantage: clean solution that will speed up the execution and simplify installation.

3. Full fix:

1. Either extract those parts from EMOSLIB which are actually needed and bundle them with calc_etadot, or rewrite the code to use fftw instead (recommended by ECMWF). For details of this library, see ​https://www.fftw.org/. Ideally combined with 2. Quick fix.

2. Install the EMOSLIB manually, even on ECMWF servers.

In any case, the documentation needs to be adapted.

[pesei]

Note that the FORD documentation does not properly recognise all of the external subroutines and functions: ​https://www.flexpart.eu/flex_extract/Documentation/Api/Fortran/lists/procedures.html
jsppole is not found, and a number of arrays is erroneously identifed as calls to external program units. We used v6.0, now there is 6.1.6, could try again.

[anphi]

I am going to work on option number 2 within the next couple months.