Treatment of singular equation systems in source code FMUs

[Rüdiger Franke]

OMCompiler comes with the LAPACK solver 3rdParty/dgesv that "is based on ​https://github.com/sjoelund/dgesv"

This enables the solution of linear equation systems with a call of the form:

  dgesv_(&_dimSys, &dimRHS, _A, &_dimSys, _ihelpArray, _b, &_dimSys, &irtrn);

  if (irtrn != 0) {
    throw ModelicaSimulationError(ALGLOOP_SOLVER, "error solving linear system (dgesv info: " + to_string(irtrn) + ")");
  }

Solvers of the simulation runtimes are able to treat such errors. This is useful in cases where equation systems become singular due to switches inside a model, if parts of the model disappear and the respective variables shall become zero.

FMUs should also treat such errors. LAPACK offers the additional functions dgetc2 and dgesc2 for this:

    dgesv_(&_dimSys, &dimRHS, _A, &_dimSys, _ihelpArray, _b, &_dimSys, &irtrn);

    if  (irtrn != 0) {
      dgetc2_(&_dimSys, _A, &_dimSys, _ihelpArray, _jhelpArray, &irtrn);
      dgesc2_(&_dimSys, _A, &_dimSys, _b, _ihelpArray, _jhelpArray, _scale);
      LOGGER_WRITE("LinearSolver: Linear system singular, using perturbed system matrix.", LC_LS, LL_DEBUG);
    }

Please extend 3rdParty/dgesv with the the functions dgetc2 and dgesc2.

[Martin Sjölund]

​https://github.com/sjoelund/dgesv/pull/1 adds the required files for dgetc2, dgesc2. I don't have time to test if it works with the FMUs so I won't merge it though.

[Rüdiger Franke]

Looks good!

I replaced my local directory OpenModelica/OMCompiler/3rdParty/dgesv with the branch ticket4747 of https://github.com/sjoelund/dgesv. Additionally I added the code of the ticket opener to the linear solver embedded with the FMU.

Compilation of OpenModelica and the FMU export worked without problem. An example that failed before does simulate now -- showing the LOGGER_WRITE message to prove that dgetc2/dgesc2 are used.

Can you merge your pull request, so that I can push my extension of the linear solver?

[Martin Sjölund]

ad98b03 now has the files added. I guess it would be good if the C runtime would also call dgetc2/dgesc2.

[Rüdiger Franke]

The link ad98b03 appears broken. Moreover, git pull does not add the new files. A synchronization issue with github?

[Martin Sjölund]

I think just a Trac issue. The tooltip gives the commit message :)

[Martin Sjölund]

0a2708a better? Seems Hudson messed up the 3rdParty commit hash so it pointed to something broken... But Trac didn't seem to update based on the changes. I guess after the next PR.

[Rüdiger Franke]

Hudson does neither get the new files, see missing symbols during FMI export:
​https://test.openmodelica.org/hudson/job/OpenModelica_TEST_PULL_REQUEST/5269/

[Martin Sjölund]

Were they added to the cmake project in the Cpp runtime? libOMCppDgesvSolver_static.a?

[Rüdiger Franke]

Implicitly yes (libOMCppDgesvSolver_static.a contains everything from the 3rdParty dgesv folder). It works as soon as I copy the new files in there.

[Adrian Pop]

Seems not to be the case somehow:

hudson@asap:~/slave/workspace/OpenModelica_TEST_PULL_REQUEST/OpenModelica/build/lib/x86_64-linux-gnu/omc/cpp$ nm libOMCppDgesvSolver_static.a | grep dge
                 U dgesv_

[Adrian Pop]

all symbols in all the lib/omc/cpp/*.a

[Rüdiger Franke]

This is because the source files are missing. Invoke ls OpenModelica/OMCompiler/3rdParty/dgesv/lapack. This should result in:

dgesc2.c  dgetc2.c  dgetrf.c  dlabad.c  dlaswp.c  ilaenv.c  xerbla.c
dgesv.c   dgetf2.c  dgetrs.c  dlamch.c  ieeeck.c  iparmq.c

including dgesc2.c and dgetc2.c.

[Adrian Pop]

Yes, that seems to be the case, in the PR job they are not there:
​https://test.openmodelica.org/hudson/view/PullRequestTesting/job/OpenModelica_TEST_PULL_REQUEST/ws/OpenModelica/OMCompiler/3rdParty/dgesv/lapack/
Note that only some people have access to Job workspace.
These are the files in OMCompiler / 3rdParty / dgesv / lapack

	dgesv.c	
	dgetf2.c
	dgetrf.c
	dgetrs.c
	dlamch.c
	dlaswp.c
	ieeeck.c
	ilaenv.c
	iparmq.c
	xerbla.c

[Adrian Pop]

Strangely the 3rdParty checked out for the PR job has hash: changeset:ad6075ab4a22aebdee753cfdeea3f2f51455ae62/OMCompiler-3rdParty which is an old one.

[Adrian Pop]

I wiped out the PR job workspace and restarted the PR.

[Adrian Pop]

Found the issue: Martin fixed the 3rdParty hash in OMCompiler but we need to update also the OpenModelica qlue project.

[Adrian Pop]

Funny, I ran some other PR which happened in the meantime.
I'm re-running yours now.

[Adrian Pop]

Ok. This is weird. Martin added the files in 3rdParty/lapack but I think that they should be in 3rdParty/dgesv/lapack. What is going on here? :)

[Adrian Pop]

I will move them to where they should be.

[Adrian Pop]

Fixed in 6d6a61aa2248fbe6ade8f71b43d7ccd0bc407b7e/OMCompiler-3rdParty.