Date: 2026-05-01T10:02:08+00:00

Actual source code: test4.c

      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain

      6:    This file is part of SLEPc.
      7:    SLEPc is distributed under a 2-clause BSD license (see LICENSE).
      8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      9: */

     11: static char help[] = "Illustrates use of MFNSetBV().\n\n"
     12:   "The command line options are:\n"
     13:   "  -t <sval>, where <sval> = scalar value that multiplies the argument.\n"
     14:   "  -file <filename>, where <filename> = matrix file in PETSc binary form.\n\n";

     16: #include <slepcmfn.h>

     18: int main(int argc,char **argv)
     19: {
     20:   Mat                A;           /* problem matrix */
     21:   MFN                mfn;
     22:   FN                 f;
     23:   BV                 V;
     24:   PetscInt           k=8;
     25:   PetscReal          norm;
     26:   PetscScalar        t=2.0;
     27:   Vec                v,y;
     28:   PetscViewer        viewer;
     29:   PetscBool          flg;
     30:   char               filename[PETSC_MAX_PATH_LEN];
     31:   MFNConvergedReason reason;

     33:   PetscFunctionBeginUser;
     34:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

     36:   PetscCall(PetscOptionsGetScalar(NULL,NULL,"-t",&t,NULL));
     37:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-k",&k,NULL));
     38:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nMatrix exponential y=exp(t*A)*e, loaded from file\n\n"));

     40:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     41:                 Load matrix A from binary file
     42:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     44:   PetscCall(PetscOptionsGetString(NULL,NULL,"-file",filename,sizeof(filename),&flg));
     45:   PetscCheck(flg,PETSC_COMM_WORLD,PETSC_ERR_USER_INPUT,"Must indicate a file name with the -file option");

     47: #if defined(PETSC_USE_COMPLEX)
     48:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Reading COMPLEX matrix from a binary file...\n"));
     49: #else
     50:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Reading REAL matrix from a binary file...\n"));
     51: #endif
     52:   PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD,filename,FILE_MODE_READ,&viewer));
     53:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
     54:   PetscCall(MatSetFromOptions(A));
     55:   PetscCall(MatLoad(A,viewer));
     56:   PetscCall(PetscViewerDestroy(&viewer));

     58:   /* set v = ones(n,1) */
     59:   PetscCall(MatCreateVecs(A,&v,&y));
     60:   PetscCall(VecSet(v,1.0));

     62:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     63:                         Create the BV object
     64:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     66:   PetscCall(BVCreate(PETSC_COMM_WORLD,&V));
     67:   PetscCall(PetscObjectSetName((PetscObject)V,"V"));
     68:   PetscCall(BVSetSizesFromVec(V,v,k));
     69:   PetscCall(BVSetFromOptions(V));

     71:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     72:                 Create the solver and set various options
     73:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     75:   PetscCall(MFNCreate(PETSC_COMM_WORLD,&mfn));
     76:   PetscCall(MFNSetOperator(mfn,A));
     77:   PetscCall(MFNSetBV(mfn,V));
     78:   PetscCall(MFNGetFN(mfn,&f));
     79:   PetscCall(FNSetType(f,FNEXP));
     80:   PetscCall(FNSetScale(f,t,1.0));
     81:   PetscCall(MFNSetDimensions(mfn,k));
     82:   PetscCall(MFNSetFromOptions(mfn));

     84:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     85:                       Solve the problem, y=exp(t*A)*v
     86:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     88:   PetscCall(MFNSolve(mfn,v,y));
     89:   PetscCall(MFNGetConvergedReason(mfn,&reason));
     90:   PetscCheck(reason>=0,PETSC_COMM_WORLD,PETSC_ERR_CONV_FAILED,"Solver did not converge");
     91:   PetscCall(VecNorm(y,NORM_2,&norm));
     92:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Computed vector at time t=%.4g has norm %g\n\n",(double)PetscRealPart(t),(double)norm));

     94:   /*
     95:      Free work space
     96:   */
     97:   PetscCall(BVDestroy(&V));
     98:   PetscCall(MFNDestroy(&mfn));
     99:   PetscCall(MatDestroy(&A));
    100:   PetscCall(VecDestroy(&v));
    101:   PetscCall(VecDestroy(&y));
    102:   PetscCall(SlepcFinalize());
    103:   return 0;
    104: }

    106: /*TEST

    108:    test:
    109:       suffix: 1
    110:       args: -file ${SLEPC_DIR}/share/slepc/datafiles/matrices/bfw62b.petsc -k 12
    111:       requires: double !complex !defined(PETSC_USE_64BIT_INDICES)

    113:    test:
    114:       suffix: 2
    115:       args: -file ${DATAFILESPATH}/matrices/complex/qc324.petsc -k 12
    116:       requires: double complex datafilespath !defined(PETSC_USE_64BIT_INDICES)

    118: TEST*/