Actual source code: ex46.c
slepc-3.17.0 2022-03-31
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 passing a sparser matrix to build the preconditioner.\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,A0; /* operator matrix */
21: EPS eps; /* eigenproblem solver context */
22: ST st;
23: PetscInt N,n=24,m,Istart,Iend,II,i,j;
24: PetscBool flag,terse;
26: SlepcInitialize(&argc,&argv,(char*)0,help);
28: PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
29: PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag);
30: if (!flag) m=n;
31: N = n*m;
32: PetscPrintf(PETSC_COMM_WORLD,"\nModified 2-D Laplacian Eigenproblem, N=%" PetscInt_FMT " (%" PetscInt_FMT "x%" PetscInt_FMT " grid)\n\n",N,n,m);
34: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
35: Compute the operator matrix A and a sparser approximation A0
36: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
38: MatCreate(PETSC_COMM_WORLD,&A);
39: MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N);
40: MatSetFromOptions(A);
41: MatSetUp(A);
42: MatGetOwnershipRange(A,&Istart,&Iend);
43: for (II=Istart;II<Iend;II++) {
44: i = II/n; j = II-i*n;
45: if (i>0) MatSetValue(A,II,II-n,-0.2,INSERT_VALUES);
46: if (i<m-1) MatSetValue(A,II,II+n,-0.2,INSERT_VALUES);
47: if (j>0) MatSetValue(A,II,II-1,-3.0,INSERT_VALUES);
48: if (j<n-1) MatSetValue(A,II,II+1,-3.0,INSERT_VALUES);
49: MatSetValue(A,II,II,7.0,INSERT_VALUES);
50: }
51: MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
52: MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
54: MatCreate(PETSC_COMM_WORLD,&A0);
55: MatSetSizes(A0,PETSC_DECIDE,PETSC_DECIDE,N,N);
56: MatSetFromOptions(A0);
57: MatSetUp(A0);
58: MatGetOwnershipRange(A0,&Istart,&Iend);
59: for (II=Istart;II<Iend;II++) {
60: i = II/n; j = II-i*n;
61: if (j>0) MatSetValue(A0,II,II-1,-3.0,INSERT_VALUES);
62: if (j<n-1) MatSetValue(A0,II,II+1,-3.0,INSERT_VALUES);
63: MatSetValue(A0,II,II,7.0,INSERT_VALUES);
64: }
65: MatAssemblyBegin(A0,MAT_FINAL_ASSEMBLY);
66: MatAssemblyEnd(A0,MAT_FINAL_ASSEMBLY);
68: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
69: Create the eigensolver and set various options
70: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
72: EPSCreate(PETSC_COMM_WORLD,&eps);
73: EPSSetOperators(eps,A,NULL);
74: EPSSetProblemType(eps,EPS_HEP);
75: EPSGetST(eps,&st);
76: STSetType(st,STSINVERT);
77: STSetPreconditionerMat(st,A0);
78: EPSSetTarget(eps,0.0);
79: EPSSetWhichEigenpairs(eps,EPS_TARGET_MAGNITUDE);
80: EPSSetFromOptions(eps);
82: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
83: Solve the eigensystem and display solution
84: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
86: EPSSolve(eps);
88: /* show detailed info unless -terse option is given by user */
89: PetscOptionsHasName(NULL,NULL,"-terse",&terse);
90: if (terse) EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
91: else {
92: PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
93: EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
94: EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
95: PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
96: }
97: EPSDestroy(&eps);
98: MatDestroy(&A);
99: MatDestroy(&A0);
100: SlepcFinalize();
101: return 0;
102: }
104: /*TEST
106: testset:
107: args: -eps_nev 4 -terse
108: output_file: output/ex46_1.out
109: requires: !single
110: test:
111: suffix: 1
112: test:
113: suffix: 2
114: args: -st_ksp_type bcgs -st_pc_type bjacobi
116: TEST*/