Actual source code: ex12.c

slepc-3.7.2 2016-07-19
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  1: /*
  2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
  4:    Copyright (c) 2002-2016, Universitat Politecnica de Valencia, Spain

  6:    This file is part of SLEPc.

  8:    SLEPc is free software: you can redistribute it and/or modify it under  the
  9:    terms of version 3 of the GNU Lesser General Public License as published by
 10:    the Free Software Foundation.

 12:    SLEPc  is  distributed in the hope that it will be useful, but WITHOUT  ANY
 13:    WARRANTY;  without even the implied warranty of MERCHANTABILITY or  FITNESS
 14:    FOR  A  PARTICULAR PURPOSE. See the GNU Lesser General Public  License  for
 15:    more details.

 17:    You  should have received a copy of the GNU Lesser General  Public  License
 18:    along with SLEPc. If not, see <http://www.gnu.org/licenses/>.
 19:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 20: */

 22: static char help[] = "Compute all eigenvalues in an interval of a symmetric-definite problem.\n\n"
 23:   "The command line options are:\n"
 24:   "  -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
 25:   "  -m <m>, where <m> = number of grid subdivisions in y dimension.\n\n";

 27: #include <slepceps.h>

 31: int main(int argc,char **argv)
 32: {
 33:   Mat            A,B;         /* matrices */
 34:   EPS            eps;         /* eigenproblem solver context */
 35:   ST             st;          /* spectral transformation context */
 36:   KSP            ksp;
 37:   PC             pc;
 38:   PetscInt       N,n=35,m,Istart,Iend,II,nev,i,j,k,*inertias;
 39:   PetscBool      flag;
 40:   PetscReal      int0,int1,*shifts;

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

 45:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
 46:   PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag);
 47:   if (!flag) m=n;
 48:   N = n*m;
 49:   PetscPrintf(PETSC_COMM_WORLD,"\nSymmetric-definite problem with two intervals, N=%D (%Dx%D grid)\n\n",N,n,m);

 51:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 52:      Compute the matrices that define the eigensystem, Ax=kBx
 53:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 55:   MatCreate(PETSC_COMM_WORLD,&A);
 56:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
 57:   MatSetFromOptions(A);
 58:   MatSetUp(A);

 60:   MatCreate(PETSC_COMM_WORLD,&B);
 61:   MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,N,N);
 62:   MatSetFromOptions(B);
 63:   MatSetUp(B);

 65:   MatGetOwnershipRange(A,&Istart,&Iend);
 66:   for (II=Istart;II<Iend;II++) {
 67:     i = II/n; j = II-i*n;
 68:     if (i>0) { MatSetValue(A,II,II-n,-1.0,INSERT_VALUES); }
 69:     if (i<m-1) { MatSetValue(A,II,II+n,-1.0,INSERT_VALUES); }
 70:     if (j>0) { MatSetValue(A,II,II-1,-1.0,INSERT_VALUES); }
 71:     if (j<n-1) { MatSetValue(A,II,II+1,-1.0,INSERT_VALUES); }
 72:     MatSetValue(A,II,II,4.0,INSERT_VALUES);
 73:     MatSetValue(B,II,II,2.0,INSERT_VALUES);
 74:   }
 75:   if (Istart==0) {
 76:     MatSetValue(B,0,0,6.0,INSERT_VALUES);
 77:     MatSetValue(B,0,1,-1.0,INSERT_VALUES);
 78:     MatSetValue(B,1,0,-1.0,INSERT_VALUES);
 79:     MatSetValue(B,1,1,1.0,INSERT_VALUES);
 80:   }

 82:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 83:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
 84:   MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY);
 85:   MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY);

 87:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 88:                 Create the eigensolver and set various options
 89:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 91:   EPSCreate(PETSC_COMM_WORLD,&eps);
 92:   EPSSetOperators(eps,A,B);
 93:   EPSSetProblemType(eps,EPS_GHEP);

 95:   /*
 96:      Set first interval and other settings for spectrum slicing
 97:   */
 98:   EPSSetWhichEigenpairs(eps,EPS_ALL);
 99:   EPSSetInterval(eps,1.1,1.3);
100:   EPSGetST(eps,&st);
101:   STSetType(st,STSINVERT);
102:   STGetKSP(st,&ksp);
103:   KSPGetPC(ksp,&pc);
104:   KSPSetType(ksp,KSPPREONLY);
105:   PCSetType(pc,PCCHOLESKY);
106:   EPSSetFromOptions(eps);

108:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
109:                  Solve for first interval and display info
110:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

112:   EPSSolve(eps);
113:   EPSGetDimensions(eps,&nev,NULL,NULL);
114:   EPSGetInterval(eps,&int0,&int1);
115:   PetscPrintf(PETSC_COMM_WORLD," Found %D eigenvalues in interval [%g,%g]\n",nev,(double)int0,(double)int1);
116:   EPSKrylovSchurGetInertias(eps,&k,&shifts,&inertias);
117:   PetscPrintf(PETSC_COMM_WORLD," Used %D shifts (inertia):\n",k);
118:   for (i=0;i<k;i++) {
119:     PetscPrintf(PETSC_COMM_WORLD," .. %g (%D)\n",(double)shifts[i],inertias[i]);
120:   }
121:   PetscFree(shifts);
122:   PetscFree(inertias);

124:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
125:                  Solve for second interval and display info
126:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
127:   EPSSetInterval(eps,1.5,1.6);
128:   EPSSolve(eps);
129:   EPSGetDimensions(eps,&nev,NULL,NULL);
130:   EPSGetInterval(eps,&int0,&int1);
131:   PetscPrintf(PETSC_COMM_WORLD," Found %D eigenvalues in interval [%g,%g]\n",nev,(double)int0,(double)int1);
132:   EPSKrylovSchurGetInertias(eps,&k,&shifts,&inertias);
133:   PetscPrintf(PETSC_COMM_WORLD," Used %D shifts (inertia):\n",k);
134:   for (i=0;i<k;i++) {
135:     PetscPrintf(PETSC_COMM_WORLD," .. %g (%D)\n",(double)shifts[i],inertias[i]);
136:   }
137:   PetscFree(shifts);
138:   PetscFree(inertias);

140:   EPSDestroy(&eps);
141:   MatDestroy(&A);
142:   MatDestroy(&B);
143:   SlepcFinalize();
144:   return ierr;
145: }