Actual source code: test11.c

slepc-3.17.2 2022-08-09
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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:   SlepcInitialize(&argc,&argv,(char*)0,help);

 55:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
 56:   PetscOptionsGetReal(NULL,NULL,"-mu",&mu,NULL);
 57:   PetscOptionsGetReal(NULL,NULL,"-tau",&tau,NULL);
 58:   PetscOptionsGetReal(NULL,NULL,"-kappa",&kappa,NULL);
 59:   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);

 61:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 62:      Compute the matrices that define the eigensystem, (k^2*M+k*C+K)x=0
 63:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

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

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

103:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
104:                 Create the eigensolver and set various options
105:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

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

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

137:   PEPSetFromOptions(pep);

139:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
140:                       Solve the eigensystem
141:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

143:   PEPSolve(pep);

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

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

162: /*
163:     Function for user-defined stopping test.

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

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

191: /*TEST

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

197: TEST*/