Actual source code: test27.c
slepc-3.18.3 2023-03-24
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[] = "Illustrates feeding exact eigenvectors as initial vectors of a second solve.\n\n"
12: "Based on ex2.\n"
13: "The command line options are:\n"
14: " -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
15: " -m <m>, where <m> = number of grid subdivisions in y dimension.\n\n";
17: #include <slepceps.h>
19: int main(int argc,char **argv)
20: {
21: Mat A;
22: EPS eps;
23: PetscInt N,n=10,m,Istart,Iend,II,nev,nconv,i,j,neigs=5;
24: PetscBool flag,terse;
25: Vec v,*X;
28: SlepcInitialize(&argc,&argv,(char*)0,help);
29: PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
30: PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag);
31: if (!flag) m=n;
32: N = n*m;
33: PetscOptionsGetInt(NULL,NULL,"-neigs",&neigs,NULL);
34: PetscPrintf(PETSC_COMM_WORLD,"\n2-D Laplacian Eigenproblem, N=%" PetscInt_FMT " (%" PetscInt_FMT "x%" PetscInt_FMT " grid), neigs=%" PetscInt_FMT "\n\n",N,n,m,neigs);
36: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
37: Create the 2-D Laplacian
38: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
40: MatCreate(PETSC_COMM_WORLD,&A);
41: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
42: MatSetFromOptions(A);
43: MatSetUp(A);
44: MatGetOwnershipRange(A,&Istart,&Iend);
45: for (II=Istart;II<Iend;II++) {
46: i = II/n; j = II-i*n;
47: if (i>0) MatSetValue(A,II,II-n,-1.0,INSERT_VALUES);
48: if (i<m-1) MatSetValue(A,II,II+n,-1.0,INSERT_VALUES);
49: if (j>0) MatSetValue(A,II,II-1,-1.0,INSERT_VALUES);
50: if (j<n-1) MatSetValue(A,II,II+1,-1.0,INSERT_VALUES);
51: MatSetValue(A,II,II,4.0,INSERT_VALUES);
52: }
53: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
54: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
55: MatCreateVecs(A,&v,NULL);
57: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
58: Create the eigensolver and set various options
59: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
61: EPSCreate(PETSC_COMM_WORLD,&eps);
62: EPSSetOperators(eps,A,NULL);
63: EPSSetProblemType(eps,EPS_HEP);
64: EPSSetWhichEigenpairs(eps,EPS_SMALLEST_REAL);
65: EPSSetDimensions(eps,neigs,PETSC_DEFAULT,PETSC_DEFAULT);
66: EPSSetFromOptions(eps);
68: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
69: Solve the eigensystem for the first time
70: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
72: EPSSolve(eps);
73: EPSGetDimensions(eps,&nev,NULL,NULL);
74: PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %" PetscInt_FMT "\n",nev);
76: EPSGetConverged(eps,&nconv);
78: VecDuplicateVecs(v,neigs,&X);
79: for (i=0;i<neigs;i++) EPSGetEigenvector(eps,i,X[i],NULL);
81: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
82: Display solution of first solve
83: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
85: PetscOptionsHasName(NULL,NULL,"-terse",&terse);
86: if (terse) EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
87: else {
88: PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
89: EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
90: EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
91: PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
92: }
94: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
95: Solve the eigensystem again, feeding the initial vectors
96: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
98: PetscPrintf(PETSC_COMM_WORLD," Solving again with eigenvectors as initial guesses\n");
99: EPSSetInitialSpace(eps,neigs,X);
100: EPSSolve(eps);
102: if (terse) EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
103: else {
104: PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
105: EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
106: EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
107: PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
108: }
110: VecDestroy(&v);
111: VecDestroyVecs(neigs,&X);
112: EPSDestroy(&eps);
113: MatDestroy(&A);
114: SlepcFinalize();
115: return 0;
116: }
118: /*TEST
120: test:
121: suffix: 1
122: args: -eps_type {{gd jd rqcg lobpcg}} -terse
124: testset:
125: args: -eps_interval .17,1.3 -terse
126: filter: grep -v "requested"
127: output_file: output/test27_2.out
128: test:
129: suffix: 2
130: args: -st_type filter -st_filter_degree 150 -eps_nev 1
131: requires: !single
132: test:
133: suffix: 2_evsl
134: nsize: {{1 2}}
135: args: -eps_type evsl
136: requires: evsl
138: TEST*/