Date: 2024-10-28T09:14:05+00:00

Actual source code: test11.c
slepc-3.22.1 2024-10-28
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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;

     53:   PetscFunctionBeginUser;
     54:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

     56:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
     57:   PetscCall(PetscOptionsGetReal(NULL,NULL,"-mu",&mu,NULL));
     58:   PetscCall(PetscOptionsGetReal(NULL,NULL,"-tau",&tau,NULL));
     59:   PetscCall(PetscOptionsGetReal(NULL,NULL,"-kappa",&kappa,NULL));
     60:   PetscCall(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:   PetscCall(MatCreate(PETSC_COMM_WORLD,&K));
     68:   PetscCall(MatSetSizes(K,PETSC_DECIDE,PETSC_DECIDE,n,n));
     69:   PetscCall(MatSetFromOptions(K));
     70:   PetscCall(MatGetOwnershipRange(K,&Istart,&Iend));
     71:   for (i=Istart;i<Iend;i++) {
     72:     if (i>0) PetscCall(MatSetValue(K,i,i-1,-kappa,INSERT_VALUES));
     73:     PetscCall(MatSetValue(K,i,i,kappa*3.0,INSERT_VALUES));
     74:     if (i<n-1) PetscCall(MatSetValue(K,i,i+1,-kappa,INSERT_VALUES));
     75:   }
     76:   PetscCall(MatAssemblyBegin(K,MAT_FINAL_ASSEMBLY));
     77:   PetscCall(MatAssemblyEnd(K,MAT_FINAL_ASSEMBLY));

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

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

    101:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    102:                 Create the eigensolver and set various options
    103:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    105:   PetscCall(PEPCreate(PETSC_COMM_WORLD,&pep));
    106:   A[0] = K; A[1] = C; A[2] = M;
    107:   PetscCall(PEPSetOperators(pep,3,A));
    108:   PetscCall(PEPSetProblemType(pep,PEP_GENERAL));

    110:   /*
    111:      Define the region containing the eigenvalues of interest
    112:   */
    113:   PetscCall(PEPGetRG(pep,&rg));
    114:   PetscCall(RGSetType(rg,RGINTERVAL));
    115:   PetscCall(RGIntervalSetEndpoints(rg,-0.5057,-0.5052,-0.001,0.001));
    116:   PetscCall(PEPSetTarget(pep,-0.43));
    117:   PetscCall(PEPSetWhichEigenpairs(pep,PEP_TARGET_MAGNITUDE));
    118:   PetscCall(PEPGetST(pep,&st));
    119:   PetscCall(STSetType(st,STSINVERT));

    121:   /*
    122:      Set solver options. In particular, we must allocate sufficient
    123:      storage for all eigenpairs that may converge (ncv). This is
    124:      application-dependent.
    125:   */
    126:   mpd = 40;
    127:   PetscCall(PEPSetDimensions(pep,2*mpd,3*mpd,mpd));
    128:   PetscCall(PEPSetTolerances(pep,SLEPC_DEFAULT_TOL,2000));
    129:   PetscCall(PetscNew(&ctx));
    130:   ctx->lastnconv = 0;
    131:   ctx->nreps     = 0;
    132:   PetscCall(PEPSetStoppingTestFunction(pep,MyStoppingTest,(void*)ctx,NULL));

    134:   PetscCall(PEPSetFromOptions(pep));

    136:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    137:                       Solve the eigensystem
    138:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    140:   PetscCall(PEPSolve(pep));

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

    150:   PetscCall(PEPDestroy(&pep));
    151:   PetscCall(MatDestroy(&M));
    152:   PetscCall(MatDestroy(&C));
    153:   PetscCall(MatDestroy(&K));
    154:   PetscCall(PetscFree(ctx));
    155:   PetscCall(SlepcFinalize());
    156:   return 0;
    157: }

    159: /*
    160:     Function for user-defined stopping test.

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

    172:   PetscFunctionBeginUser;
    173:   /* check usual termination conditions, but ignoring the case nconv>=nev */
    174:   PetscCall(PEPStoppingBasic(pep,its,max_it,nconv,PETSC_INT_MAX,reason,NULL));
    175:   if (*reason==PEP_CONVERGED_ITERATING) {
    176:     /* check if nconv is the same as before */
    177:     if (nconv==ctx->lastnconv) ctx->nreps++;
    178:     else {
    179:       ctx->lastnconv = nconv;
    180:       ctx->nreps     = 0;
    181:     }
    182:     /* check if no eigenvalues converged in last 10 restarts */
    183:     if (nconv && ctx->nreps>10) *reason = PEP_CONVERGED_USER;
    184:   }
    185:   PetscFunctionReturn(PETSC_SUCCESS);
    186: }

    188: /*TEST

    190:    test:
    191:       args: -terse
    192:       requires: !single
    193:       suffix: 1

    195: TEST*/