Date: 2026-03-09T09:12:32+00:00

Actual source code: ex44.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[] = "Compute rightmost eigenvalues with Lyapunov inverse iteration.\n\n"
     12:   "Loads matrix from a file or builds the same problem as ex36.c (with fixed parameters).\n\n"
     13:   "The command line options are:\n"
     14:   "  -file <filename>, where <filename> = matrix file in PETSc binary form.\n"
     15:   "  -shift <sigma>, shift to make the matrix stable.\n"
     16:   "  -n <n>, block dimension of the 2x2 block matrix (if matrix is generated).\n\n";

     18: #include <slepceps.h>

     20: int main(int argc,char **argv)
     21: {
     22:   Mat            A;               /* operator matrix */
     23:   EPS            eps;             /* eigenproblem solver context */
     24:   EPSType        type;
     25:   PetscScalar    alpha,beta,tau1,tau2,delta1,delta2,L,h,sigma=0.0;
     26:   PetscInt       n=30,i,Istart,Iend,nev;
     27:   char           filename[PETSC_MAX_PATH_LEN];
     28:   PetscViewer    viewer;
     29:   PetscBool      flg,terse;

     31:   PetscFunctionBeginUser;
     32:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

     34:   PetscCall(PetscOptionsGetString(NULL,NULL,"-file",filename,sizeof(filename),&flg));
     35:   if (flg) {

     37:     /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     38:                         Load the matrix from file
     39:        - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
     40:     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nEigenproblem stored in file.\n\n"));
     41: #if defined(PETSC_USE_COMPLEX)
     42:     PetscCall(PetscPrintf(PETSC_COMM_WORLD," Reading COMPLEX matrix from a binary file...\n"));
     43: #else
     44:     PetscCall(PetscPrintf(PETSC_COMM_WORLD," Reading REAL matrix from a binary file...\n"));
     45: #endif
     46:     PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD,filename,FILE_MODE_READ,&viewer));
     47:     PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
     48:     PetscCall(MatSetFromOptions(A));
     49:     PetscCall(MatLoad(A,viewer));
     50:     PetscCall(PetscViewerDestroy(&viewer));

     52:   } else {

     54:     /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     55:           Generate Brusselator matrix
     56:        - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
     57:     PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
     58:     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nBrusselator wave model, n=%" PetscInt_FMT "\n\n",n));

     60:     alpha  = 2.0;
     61:     beta   = 5.45;
     62:     delta1 = 0.008;
     63:     delta2 = 0.004;
     64:     L      = 0.51302;

     66:     h = 1.0 / (PetscReal)(n+1);
     67:     tau1 = delta1 / ((h*L)*(h*L));
     68:     tau2 = delta2 / ((h*L)*(h*L));

     70:     PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
     71:     PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,2*n,2*n));
     72:     PetscCall(MatSetFromOptions(A));

     74:     PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
     75:     for (i=Istart;i<Iend;i++) {
     76:       if (i<n) {  /* upper blocks */
     77:         if (i>0) PetscCall(MatSetValue(A,i,i-1,tau1,INSERT_VALUES));
     78:         if (i<n-1) PetscCall(MatSetValue(A,i,i+1,tau1,INSERT_VALUES));
     79:         PetscCall(MatSetValue(A,i,i,-2.0*tau1+beta-1.0,INSERT_VALUES));
     80:         PetscCall(MatSetValue(A,i,i+n,alpha*alpha,INSERT_VALUES));
     81:       } else {  /* lower blocks */
     82:         if (i>n) PetscCall(MatSetValue(A,i,i-1,tau2,INSERT_VALUES));
     83:         if (i<2*n-1) PetscCall(MatSetValue(A,i,i+1,tau2,INSERT_VALUES));
     84:         PetscCall(MatSetValue(A,i,i,-2.0*tau2-alpha*alpha,INSERT_VALUES));
     85:         PetscCall(MatSetValue(A,i,i-n,-beta,INSERT_VALUES));
     86:       }
     87:     }
     88:     PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
     89:     PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));
     90:   }

     92:   /* Shift the matrix to make it stable, A-sigma*I */
     93:   PetscCall(PetscOptionsGetScalar(NULL,NULL,"-shift",&sigma,NULL));
     94:   PetscCall(MatShift(A,-sigma));

     96:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     97:                 Create the eigensolver and set various options
     98:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    100:   PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));
    101:   PetscCall(EPSSetOperators(eps,A,NULL));
    102:   PetscCall(EPSSetProblemType(eps,EPS_NHEP));
    103:   PetscCall(EPSSetWhichEigenpairs(eps,EPS_LARGEST_REAL));
    104:   PetscCall(EPSSetFromOptions(eps));

    106:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    107:                       Solve the eigensystem
    108:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    110:   PetscCall(EPSSolve(eps));
    111:   PetscCall(EPSGetType(eps,&type));
    112:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type));
    113:   PetscCall(EPSGetDimensions(eps,&nev,NULL,NULL));
    114:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %" PetscInt_FMT "\n",nev));

    116:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    117:                     Display solution and clean up
    118:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    120:   /* show detailed info unless -terse option is given by user */
    121:   PetscCall(PetscOptionsHasName(NULL,NULL,"-terse",&terse));
    122:   if (terse) PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));
    123:   else {
    124:     PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL));
    125:     PetscCall(EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD));
    126:     PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD));
    127:     PetscCall(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD));
    128:   }
    129:   PetscCall(EPSDestroy(&eps));
    130:   PetscCall(MatDestroy(&A));
    131:   PetscCall(SlepcFinalize());
    132:   return 0;
    133: }

    135: /*TEST

    137:    testset:
    138:       args: -eps_nev 6 -shift 0.1 -eps_type {{krylovschur lyapii}} -eps_tol 1e-7 -terse
    139:       requires: double
    140:       filter: grep -v method | sed -e "s/-0.09981-2.13938i, -0.09981+2.13938i/-0.09981+2.13938i, -0.09981-2.13938i/" | sed -e "s/-0.77192-2.52712i, -0.77192+2.52712i/-0.77192+2.52712i, -0.77192-2.52712i/" | sed -e "s/-1.88445-3.02666i, -1.88445+3.02666i/-1.88445+3.02666i, -1.88445-3.02666i/"
    141:       output_file: output/ex44_1.out
    142:       test:
    143:          suffix: 1
    144:       test:
    145:          suffix: 2
    146:          args: -eps_lyapii_ranks 8,20 -options_left no

    148:    test:
    149:       suffix: 3
    150:       args: -file ${SLEPC_DIR}/share/slepc/datafiles/matrices/rdb200.petsc -shift 35 -eps_type {{krylovschur lyapii}} -terse
    151:       requires: double !complex !defined(PETSC_USE_64BIT_INDICES)
    152:       filter: grep -v method

    154: TEST*/