Actual source code: ex12.c
slepc-3.17.2 2022-08-09
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: */
11: static char help[] = "Compute all eigenvalues in an interval of a symmetric-definite problem.\n\n"
12: "The command line options are:\n"
13: " -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
14: " -m <m>, where <m> = number of grid subdivisions in y dimension.\n\n";
16: #include <slepceps.h>
18: int main(int argc,char **argv)
19: {
20: Mat A,B; /* matrices */
21: EPS eps; /* eigenproblem solver context */
22: ST st; /* spectral transformation context */
23: KSP ksp;
24: PC pc;
25: PetscInt N,n=35,m,Istart,Iend,II,nev,i,j,k,*inertias;
26: PetscBool flag,showinertia=PETSC_TRUE;
27: PetscReal int0,int1,*shifts;
29: SlepcInitialize(&argc,&argv,(char*)0,help);
31: PetscOptionsGetBool(NULL,NULL,"-showinertia",&showinertia,NULL);
32: PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
33: PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag);
34: if (!flag) m=n;
35: N = n*m;
36: PetscPrintf(PETSC_COMM_WORLD,"\nSymmetric-definite problem with two intervals, N=%" PetscInt_FMT " (%" PetscInt_FMT "x%" PetscInt_FMT " grid)\n\n",N,n,m);
38: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
39: Compute the matrices that define the eigensystem, Ax=kBx
40: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
42: MatCreate(PETSC_COMM_WORLD,&A);
43: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
44: MatSetFromOptions(A);
45: MatSetUp(A);
47: MatCreate(PETSC_COMM_WORLD,&B);
48: MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,N,N);
49: MatSetFromOptions(B);
50: MatSetUp(B);
52: MatGetOwnershipRange(A,&Istart,&Iend);
53: for (II=Istart;II<Iend;II++) {
54: i = II/n; j = II-i*n;
55: if (i>0) MatSetValue(A,II,II-n,-1.0,INSERT_VALUES);
56: if (i<m-1) MatSetValue(A,II,II+n,-1.0,INSERT_VALUES);
57: if (j>0) MatSetValue(A,II,II-1,-1.0,INSERT_VALUES);
58: if (j<n-1) MatSetValue(A,II,II+1,-1.0,INSERT_VALUES);
59: MatSetValue(A,II,II,4.0,INSERT_VALUES);
60: MatSetValue(B,II,II,2.0,INSERT_VALUES);
61: }
62: if (Istart==0) {
63: MatSetValue(B,0,0,6.0,INSERT_VALUES);
64: MatSetValue(B,0,1,-1.0,INSERT_VALUES);
65: MatSetValue(B,1,0,-1.0,INSERT_VALUES);
66: MatSetValue(B,1,1,1.0,INSERT_VALUES);
67: }
69: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
70: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
71: MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY);
72: MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY);
74: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
75: Create the eigensolver and set various options
76: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
78: EPSCreate(PETSC_COMM_WORLD,&eps);
79: EPSSetOperators(eps,A,B);
80: EPSSetProblemType(eps,EPS_GHEP);
82: /*
83: Set first interval and other settings for spectrum slicing
84: */
85: EPSSetType(eps,EPSKRYLOVSCHUR);
86: EPSSetWhichEigenpairs(eps,EPS_ALL);
87: EPSSetInterval(eps,1.1,1.3);
88: EPSGetST(eps,&st);
89: STSetType(st,STSINVERT);
90: EPSKrylovSchurGetKSP(eps,&ksp);
91: KSPGetPC(ksp,&pc);
92: KSPSetType(ksp,KSPPREONLY);
93: PCSetType(pc,PCCHOLESKY);
94: EPSSetFromOptions(eps);
96: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
97: Solve for first interval and display info
98: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
100: EPSSolve(eps);
101: EPSGetDimensions(eps,&nev,NULL,NULL);
102: EPSGetInterval(eps,&int0,&int1);
103: PetscPrintf(PETSC_COMM_WORLD," Found %" PetscInt_FMT " eigenvalues in interval [%g,%g]\n",nev,(double)int0,(double)int1);
104: if (showinertia) {
105: EPSKrylovSchurGetInertias(eps,&k,&shifts,&inertias);
106: PetscPrintf(PETSC_COMM_WORLD," Used %" PetscInt_FMT " shifts (inertia):\n",k);
107: for (i=0;i<k;i++) PetscPrintf(PETSC_COMM_WORLD," .. %g (%" PetscInt_FMT ")\n",(double)shifts[i],inertias[i]);
108: PetscFree(shifts);
109: PetscFree(inertias);
110: }
112: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
113: Solve for second interval and display info
114: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
115: EPSSetInterval(eps,1.499,1.6);
116: EPSSolve(eps);
117: EPSGetDimensions(eps,&nev,NULL,NULL);
118: EPSGetInterval(eps,&int0,&int1);
119: PetscPrintf(PETSC_COMM_WORLD," Found %" PetscInt_FMT " eigenvalues in interval [%g,%g]\n",nev,(double)int0,(double)int1);
120: if (showinertia) {
121: EPSKrylovSchurGetInertias(eps,&k,&shifts,&inertias);
122: PetscPrintf(PETSC_COMM_WORLD," Used %" PetscInt_FMT " shifts (inertia):\n",k);
123: for (i=0;i<k;i++) PetscPrintf(PETSC_COMM_WORLD," .. %g (%" PetscInt_FMT ")\n",(double)shifts[i],inertias[i]);
124: PetscFree(shifts);
125: PetscFree(inertias);
126: }
128: EPSDestroy(&eps);
129: MatDestroy(&A);
130: MatDestroy(&B);
131: SlepcFinalize();
132: return 0;
133: }
135: /*TEST
137: test:
138: suffix: 1
139: args: -showinertia 0 -eps_error_relative
140: requires: !single
142: TEST*/