Date: 2021-09-20T09:44:06+00:00

Actual source code: test11.c
slepc-3.15.2 2021-09-20
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-2021, 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;
     50:   PetscViewer    viewer;
     51:   PetscInt       n=30,Istart,Iend,i,mpd;
     52:   PetscReal      mu=1.0,tau=10.0,kappa=5.0;

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

     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=%D 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) {
     74:       MatSetValue(K,i,i-1,-kappa,INSERT_VALUES);
     75:     }
     76:     MatSetValue(K,i,i,kappa*3.0,INSERT_VALUES);
     77:     if (i<n-1) {
     78:       MatSetValue(K,i,i+1,-kappa,INSERT_VALUES);
     79:     }
     80:   }
     81:   MatAssemblyBegin(K,MAT_FINAL_ASSEMBLY);
     82:   MatAssemblyEnd(K,MAT_FINAL_ASSEMBLY);

     84:   /* C is a tridiagonal */
     85:   MatCreate(PETSC_COMM_WORLD,&C);
     86:   MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,n,n);
     87:   MatSetFromOptions(C);
     88:   MatSetUp(C);
     89:   MatGetOwnershipRange(C,&Istart,&Iend);
     90:   for (i=Istart;i<Iend;i++) {
     91:     if (i>0) {
     92:       MatSetValue(C,i,i-1,-tau,INSERT_VALUES);
     93:     }
     94:     MatSetValue(C,i,i,tau*3.0,INSERT_VALUES);
     95:     if (i<n-1) {
     96:       MatSetValue(C,i,i+1,-tau,INSERT_VALUES);
     97:     }
     98:   }
     99:   MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
    100:   MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);

    102:   /* M is a diagonal matrix */
    103:   MatCreate(PETSC_COMM_WORLD,&M);
    104:   MatSetSizes(M,PETSC_DECIDE,PETSC_DECIDE,n,n);
    105:   MatSetFromOptions(M);
    106:   MatSetUp(M);
    107:   MatGetOwnershipRange(M,&Istart,&Iend);
    108:   for (i=Istart;i<Iend;i++) {
    109:     MatSetValue(M,i,i,mu,INSERT_VALUES);
    110:   }
    111:   MatAssemblyBegin(M,MAT_FINAL_ASSEMBLY);
    112:   MatAssemblyEnd(M,MAT_FINAL_ASSEMBLY);

    114:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    115:                 Create the eigensolver and set various options
    116:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    118:   PEPCreate(PETSC_COMM_WORLD,&pep);
    119:   A[0] = K; A[1] = C; A[2] = M;
    120:   PEPSetOperators(pep,3,A);
    121:   PEPSetProblemType(pep,PEP_GENERAL);
    122:   PEPSetTolerances(pep,PETSC_SMALL,PETSC_DEFAULT);

    124:   /*
    125:      Define the region containing the eigenvalues of interest
    126:   */
    127:   PEPGetRG(pep,&rg);
    128:   RGSetType(rg,RGINTERVAL);
    129:   RGIntervalSetEndpoints(rg,-0.5057,-0.5052,-0.001,0.001);
    130:   PEPSetTarget(pep,-0.43);
    131:   PEPSetWhichEigenpairs(pep,PEP_TARGET_MAGNITUDE);
    132:   PEPGetST(pep,&st);
    133:   STSetType(st,STSINVERT);

    135:   /*
    136:      Set solver options. In particular, we must allocate sufficient
    137:      storage for all eigenpairs that may converge (ncv). This is
    138:      application-dependent.
    139:   */
    140:   mpd = 40;
    141:   PEPSetDimensions(pep,2*mpd,3*mpd,mpd);
    142:   PEPSetTolerances(pep,PETSC_DEFAULT,2000);
    143:   PetscNew(&ctx);
    144:   ctx->lastnconv = 0;
    145:   ctx->nreps     = 0;
    146:   PEPSetStoppingTestFunction(pep,MyStoppingTest,(void*)ctx,NULL);

    148:   PEPSetFromOptions(pep);

    150:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    151:                       Solve the eigensystem
    152:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    154:   PEPSolve(pep);

    156:   /* show detailed info unless -terse option is given by user */
    157:   PetscViewerASCIIGetStdout(PETSC_COMM_WORLD,&viewer);
    158:   PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INFO_DETAIL);
    159:   PEPConvergedReasonView(pep,viewer);
    160:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
    161:   if (!terse) {
    162:     PEPErrorView(pep,PEP_ERROR_BACKWARD,viewer);
    163:   }
    164:   PetscViewerPopFormat(viewer);

    166:   PEPDestroy(&pep);
    167:   MatDestroy(&M);
    168:   MatDestroy(&C);
    169:   MatDestroy(&K);
    170:   PetscFree(ctx);
    171:   SlepcFinalize();
    172:   return ierr;
    173: }

    175: /*
    176:     Function for user-defined stopping test.

    178:     Ignores the value of nev. It only takes into account the number of
    179:     eigenpairs that have converged in recent outer iterations (restarts);
    180:     if no new eigenvalues have converged in the last few restarts,
    181:     we stop the iteration, assuming that no more eigenvalues are present
    182:     inside the region.
    183: */
    184: PetscErrorCode MyStoppingTest(PEP pep,PetscInt its,PetscInt max_it,PetscInt nconv,PetscInt nev,PEPConvergedReason *reason,void *ptr)
    185: {
    187:   CTX_SPRING     *ctx = (CTX_SPRING*)ptr;

    190:   /* check usual termination conditions, but ignoring the case nconv>=nev */
    191:   PEPStoppingBasic(pep,its,max_it,nconv,PETSC_MAX_INT,reason,NULL);
    192:   if (*reason==PEP_CONVERGED_ITERATING) {
    193:     /* check if nconv is the same as before */
    194:     if (nconv==ctx->lastnconv) ctx->nreps++;
    195:     else {
    196:       ctx->lastnconv = nconv;
    197:       ctx->nreps     = 0;
    198:     }
    199:     /* check if no eigenvalues converged in last 10 restarts */
    200:     if (nconv && ctx->nreps>10) *reason = PEP_CONVERGED_USER;
    201:   }
    202:   return(0);
    203: }

    205: /*TEST

    207:    test:
    208:       args: -terse
    209:       suffix: 1

    211: TEST*/