Date: 2023-01-26T12:19:20+00:00

Actual source code: test11.c
slepc-3.18.2 2023-01-26
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      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: */
     10: /*
     11:    Example based on spring problem in NLEVP collection [1]. See the parameters
     12:    meaning at Example 2 in [2].

     14:    [1] T. Betcke, N. J. Higham, V. Mehrmann, C. Schroder, and F. Tisseur,
     15:        NLEVP: A Collection of Nonlinear Eigenvalue Problems, MIMS EPrint
     16:        2010.98, November 2010.
     17:    [2] F. Tisseur, Backward error and condition of polynomial eigenvalue
     18:        problems, Linear Algebra and its Applications, 309 (2000), pp. 339--361,
     19:        April 2000.
     20: */

     22: static char help[] = "Illustrates the use of a user-defined stopping test.\n\n"
     23:   "The command line options are:\n"
     24:   "  -n <n> ... number of grid subdivisions.\n"
     25:   "  -mu <value> ... mass (default 1).\n"
     26:   "  -tau <value> ... damping constant of the dampers (default 10).\n"
     27:   "  -kappa <value> ... damping constant of the springs (default 5).\n\n";

     29: #include <slepcpep.h>

     31: /*
     32:    User-defined routines
     33: */
     34: PetscErrorCode MyStoppingTest(PEP,PetscInt,PetscInt,PetscInt,PetscInt,PEPConvergedReason*,void*);

     36: typedef struct {
     37:   PetscInt    lastnconv;      /* last value of nconv; used in stopping test */
     38:   PetscInt    nreps;          /* number of repetitions of nconv; used in stopping test */
     39: } CTX_SPRING;

     41: int main(int argc,char **argv)
     42: {
     43:   Mat            M,C,K,A[3];      /* problem matrices */
     44:   PEP            pep;             /* polynomial eigenproblem solver context */
     45:   RG             rg;              /* region object */
     46:   ST             st;
     47:   CTX_SPRING     *ctx;
     48:   PetscBool      terse;
     49:   PetscViewer    viewer;
     50:   PetscInt       n=30,Istart,Iend,i,mpd;
     51:   PetscReal      mu=1.0,tau=10.0,kappa=5.0;

     54:   SlepcInitialize(&argc,&argv,(char*)0,help);

     56:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
     57:   PetscOptionsGetReal(NULL,NULL,"-mu",&mu,NULL);
     58:   PetscOptionsGetReal(NULL,NULL,"-tau",&tau,NULL);
     59:   PetscOptionsGetReal(NULL,NULL,"-kappa",&kappa,NULL);
     60:   PetscPrintf(PETSC_COMM_WORLD,"\nDamped mass-spring system, n=%" PetscInt_FMT " mu=%g tau=%g kappa=%g\n\n",n,(double)mu,(double)tau,(double)kappa);

     62:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     63:      Compute the matrices that define the eigensystem, (k^2*M+k*C+K)x=0
     64:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     66:   /* K is a tridiagonal */
     67:   MatCreate(PETSC_COMM_WORLD,&K);
     68:   MatSetSizes(K,PETSC_DECIDE,PETSC_DECIDE,n,n);
     69:   MatSetFromOptions(K);
     70:   MatSetUp(K);
     71:   MatGetOwnershipRange(K,&Istart,&Iend);
     72:   for (i=Istart;i<Iend;i++) {
     73:     if (i>0) MatSetValue(K,i,i-1,-kappa,INSERT_VALUES);
     74:     MatSetValue(K,i,i,kappa*3.0,INSERT_VALUES);
     75:     if (i<n-1) MatSetValue(K,i,i+1,-kappa,INSERT_VALUES);
     76:   }
     77:   MatAssemblyBegin(K,MAT_FINAL_ASSEMBLY);
     78:   MatAssemblyEnd(K,MAT_FINAL_ASSEMBLY);

     80:   /* C is a tridiagonal */
     81:   MatCreate(PETSC_COMM_WORLD,&C);
     82:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,n,n);
     83:   MatSetFromOptions(C);
     84:   MatSetUp(C);
     85:   MatGetOwnershipRange(C,&Istart,&Iend);
     86:   for (i=Istart;i<Iend;i++) {
     87:     if (i>0) MatSetValue(C,i,i-1,-tau,INSERT_VALUES);
     88:     MatSetValue(C,i,i,tau*3.0,INSERT_VALUES);
     89:     if (i<n-1) MatSetValue(C,i,i+1,-tau,INSERT_VALUES);
     90:   }
     91:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
     92:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

     94:   /* M is a diagonal matrix */
     95:   MatCreate(PETSC_COMM_WORLD,&M);
     96:   MatSetSizes(M,PETSC_DECIDE,PETSC_DECIDE,n,n);
     97:   MatSetFromOptions(M);
     98:   MatSetUp(M);
     99:   MatGetOwnershipRange(M,&Istart,&Iend);
    100:   for (i=Istart;i<Iend;i++) MatSetValue(M,i,i,mu,INSERT_VALUES);
    101:   MatAssemblyBegin(M,MAT_FINAL_ASSEMBLY);
    102:   MatAssemblyEnd(M,MAT_FINAL_ASSEMBLY);

    104:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    105:                 Create the eigensolver and set various options
    106:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    108:   PEPCreate(PETSC_COMM_WORLD,&pep);
    109:   A[0] = K; A[1] = C; A[2] = M;
    110:   PEPSetOperators(pep,3,A);
    111:   PEPSetProblemType(pep,PEP_GENERAL);
    112:   PEPSetTolerances(pep,PETSC_SMALL,PETSC_DEFAULT);

    114:   /*
    115:      Define the region containing the eigenvalues of interest
    116:   */
    117:   PEPGetRG(pep,&rg);
    118:   RGSetType(rg,RGINTERVAL);
    119:   RGIntervalSetEndpoints(rg,-0.5057,-0.5052,-0.001,0.001);
    120:   PEPSetTarget(pep,-0.43);
    121:   PEPSetWhichEigenpairs(pep,PEP_TARGET_MAGNITUDE);
    122:   PEPGetST(pep,&st);
    123:   STSetType(st,STSINVERT);

    125:   /*
    126:      Set solver options. In particular, we must allocate sufficient
    127:      storage for all eigenpairs that may converge (ncv). This is
    128:      application-dependent.
    129:   */
    130:   mpd = 40;
    131:   PEPSetDimensions(pep,2*mpd,3*mpd,mpd);
    132:   PEPSetTolerances(pep,PETSC_DEFAULT,2000);
    133:   PetscNew(&ctx);
    134:   ctx->lastnconv = 0;
    135:   ctx->nreps     = 0;
    136:   PEPSetStoppingTestFunction(pep,MyStoppingTest,(void*)ctx,NULL);

    138:   PEPSetFromOptions(pep);

    140:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    141:                       Solve the eigensystem
    142:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    144:   PEPSolve(pep);

    146:   /* show detailed info unless -terse option is given by user */
    147:   PetscViewerASCIIGetStdout(PETSC_COMM_WORLD,&viewer);
    148:   PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INFO_DETAIL);
    149:   PEPConvergedReasonView(pep,viewer);
    150:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
    151:   if (!terse) PEPErrorView(pep,PEP_ERROR_BACKWARD,viewer);
    152:   PetscViewerPopFormat(viewer);

    154:   PEPDestroy(&pep);
    155:   MatDestroy(&M);
    156:   MatDestroy(&C);
    157:   MatDestroy(&K);
    158:   PetscFree(ctx);
    159:   SlepcFinalize();
    160:   return 0;
    161: }

    163: /*
    164:     Function for user-defined stopping test.

    166:     Ignores the value of nev. It only takes into account the number of
    167:     eigenpairs that have converged in recent outer iterations (restarts);
    168:     if no new eigenvalues have converged in the last few restarts,
    169:     we stop the iteration, assuming that no more eigenvalues are present
    170:     inside the region.
    171: */
    172: PetscErrorCode MyStoppingTest(PEP pep,PetscInt its,PetscInt max_it,PetscInt nconv,PetscInt nev,PEPConvergedReason *reason,void *ptr)
    173: {
    174:   CTX_SPRING     *ctx = (CTX_SPRING*)ptr;

    177:   /* check usual termination conditions, but ignoring the case nconv>=nev */
    178:   PEPStoppingBasic(pep,its,max_it,nconv,PETSC_MAX_INT,reason,NULL);
    179:   if (*reason==PEP_CONVERGED_ITERATING) {
    180:     /* check if nconv is the same as before */
    181:     if (nconv==ctx->lastnconv) ctx->nreps++;
    182:     else {
    183:       ctx->lastnconv = nconv;
    184:       ctx->nreps     = 0;
    185:     }
    186:     /* check if no eigenvalues converged in last 10 restarts */
    187:     if (nconv && ctx->nreps>10) *reason = PEP_CONVERGED_USER;
    188:   }
    189:   return 0;
    190: }

    192: /*TEST

    194:    test:
    195:       args: -terse
    196:       suffix: 1

    198: TEST*/