Thank you so much! I will try. Georg
Von: Dumux [mailto:dumux-boun...@listserv.uni-stuttgart.de] Im Auftrag von Flemisch, Bernd, apl.Prof.Dr. Gesendet: Montag, 11. Dezember 2017 10:31 An: DuMuX User Forum Betreff: Re: [DuMuX] Dune::BCRSMatrix In that case (numSurfaceReactions > numSurfaceSpecies), you have to go for a least-squares solution min_{x in R^numSurfaceSpecies} || A*x - b || which can be achieved by solving (A^t*A)*x = b I have not seen a dedicated ISTL solver for this. My indexing was wrong in the first place. You should modify to Dune::FieldMatrix<Scalar, numSurfaceReactions, numSurfaceSpecies> A; Dune::FieldMatrix<Scalar, numSurfaceSpecies, numSurfaceReactions> At; for(int speciesIdx=0; speciesIdx<numSurfaceSpecies; speciesIdx++) for(int reactionIdx=0; reactionIdx<numSurfaceReactions; reactionIdx++) { A[reactionIdx][speciesIdx] = ... At[speciesIdx][reactionIdx] = ... } auto AtA = A.leftmultiply(At); // right hand side Dune::FieldVector<Scalar, numSurfaceReactions> b; for(int reactionIdx=0; reactionIdx<numSurfaceReactions; reactionIdx++) b[reactionIdx] = ... // solution Dune::FieldVector<Scalar, numSurfaceSpecies> x; AtA.solve(x, b); ________________________________ Von: Dumux <dumux-boun...@listserv.uni-stuttgart.de<mailto:dumux-boun...@listserv.uni-stuttgart.de>> im Auftrag von georg.fut...@dlr.de<mailto:georg.fut...@dlr.de> <georg.fut...@dlr.de<mailto:georg.fut...@dlr.de>> Gesendet: Montag, 11. Dezember 2017 10:10:20 An: dumux@listserv.uni-stuttgart.de<mailto:dumux@listserv.uni-stuttgart.de> Betreff: Re: [DuMuX] Dune::BCRSMatrix Hi Bernd, Actually, the system might be overdetermined, so FieldMatrix solve() will not necessarily work. Do I have any options to solve such a system with ISTL? Kind regards Georg Von: Dumux [mailto:dumux-boun...@listserv.uni-stuttgart.de] Im Auftrag von Flemisch, Bernd, apl.Prof.Dr. Gesendet: Montag, 11. Dezember 2017 10:03 An: DuMuX User Forum Betreff: Re: [DuMuX] Dune::BCRSMatrix Hi Georg, for the system that you describe, there is no need to wrap things in BCRSMatrices and BlockVectors. You can use directly FieldMatrices and -Vectors: Dune::FieldMatrix<Scalar, numSurfaceReactions, numSurfaceSpecies> A; for(int speciesIdx=0; speciesIdx<numSurfaceSpecies; speciesIdx++) for(int reactionIdx=0; reactionIdx<numSurfaceReactions; reactionIdx++) A[speciesIdx][reactionIdx] = ... // right hand side Dune::FieldVector<Scalar, numSurfaceReactions> b; for(int reactionIdx=0; reactionIdx<numSurfaceReactions; reactionIdx++) b[reactionIdx] = ... // solution Dune::FieldVector<Scalar, numSurfaceSpecies> x; A.solve(x, b); I hope that numSurfaceReactions == numSurfaceSpecies? You would only need the more complicated setting if your system size was not known at compile time. Kind regards Bernd ________________________________ Von: Dumux <dumux-boun...@listserv.uni-stuttgart.de<mailto:dumux-boun...@listserv.uni-stuttgart.de>> im Auftrag von georg.fut...@dlr.de<mailto:georg.fut...@dlr.de> <georg.fut...@dlr.de<mailto:georg.fut...@dlr.de>> Gesendet: Montag, 11. Dezember 2017 09:29:07 An: dumux@listserv.uni-stuttgart.de<mailto:dumux@listserv.uni-stuttgart.de> Betreff: [DuMuX] Dune::BCRSMatrix Hello Dumux, I would like to solve a linear system of equations (A*x = b) using the Dune ISTL. To use the Dumux implementation (seqsolverbackend.hh), Dune::FieldVectors need to be wrapped in Dune::Blockvectors and a Dune::FieldMatrix is wrapped in a Dune::BCRSMatrix. I am not familiar with these data types and the Dune documentation on the homepage is really confusing. Since the system is not too large, I guess I can solve everything in a single block? This is the code I use right now: Dune::FieldMatrix<Scalar, numSurfaceReactions, numSurfaceSpecies> A; for(int speciesIdx=0; speciesIdx<numSurfaceSpecies; speciesIdx++) for(int reactionIdx=0; reactionIdx<numSurfaceReactions; reactionIdx++) assign values... // right hand side Dune::BlockVector<Dune::FieldVector<Scalar, numSurfaceReactions> > b; b.resize(1); // does this mean there is only one block containing a FieldVector ? for(int reactionIdx=0; reactionIdx<numSurfaceReactions; reactionIdx++) b[0][reactionIdx] = ... // solution Dune::BlockVector<Dune::FieldVector<Scalar, numSurfaceSpecies> > x; x.resize(1); typedef typename Dune::FieldMatrix<Scalar, numSurfaceReactions, numSurfaceSpecies> MatrixBlock; typedef typename Dune::BCRSMatrix<MatrixBlock> ISTLMatrix; ISTLMatrix A2(1, 1, ISTLMatrix::random); // does this mean there is only one block containing a FieldMatrix ? for(int speciesIdx=0; speciesIdx<numSurfaceSpecies; speciesIdx++) for(int reactionIdx=0; reactionIdx<numSurfaceReactions; reactionIdx++) A2[0][0][reactionIdx][speciesIdx] = ... HOW TO ASSIGN VALUES??? I get a segmentation fault from the last line. Is there better information on BCRS matrices somewhere? Any hints on how to set up this matrix are greatly appreciated! Best regards Georg Futter -------------------------- German Aerospace Center (DLR) Institute of Engineering Thermodynamics | Computational Electrochemistry | Pfaffenwaldring 38-40 | 70569 Stuttgart Dipl.-Ing. Georg Futter | Ph.D. student Telefon 0711/6862-8135 | georg.fut...@dlr.de<mailto:georg.fut...@dlr.de> www.DLR.de<http://www.dlr.de/>
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