Line data Source code
1 : /*
2 : - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
3 : SLEPc - Scalable Library for Eigenvalue Problem Computations
4 : Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain
5 :
6 : This file is part of SLEPc.
7 : SLEPc is distributed under a 2-clause BSD license (see LICENSE).
8 : - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
9 : */
10 : /*
11 : This example implements one of the problems found at
12 : NLEVP: A Collection of Nonlinear Eigenvalue Problems,
13 : The University of Manchester.
14 : The details of the collection can be found at:
15 : [1] T. Betcke et al., "NLEVP: A Collection of Nonlinear Eigenvalue
16 : Problems", ACM Trans. Math. Software 39(2), Article 7, 2013.
17 :
18 : The loaded_string problem is a rational eigenvalue problem for the
19 : finite element model of a loaded vibrating string.
20 : */
21 :
22 : static char help[] = "Test the NLEIGS solver with FNCOMBINE.\n\n"
23 : "This is based on loaded_string from the NLEVP collection.\n"
24 : "The command line options are:\n"
25 : " -n <n>, dimension of the matrices.\n"
26 : " -kappa <kappa>, stiffness of elastic spring.\n"
27 : " -mass <m>, mass of the attached load.\n\n";
28 :
29 : #include <slepcnep.h>
30 :
31 : #define NMAT 3
32 :
33 1 : int main(int argc,char **argv)
34 : {
35 1 : Mat A[NMAT]; /* problem matrices */
36 1 : FN f[NMAT],g; /* functions to define the nonlinear operator */
37 1 : NEP nep; /* nonlinear eigensolver context */
38 1 : PetscInt n=100,Istart,Iend,i;
39 1 : PetscReal kappa=1.0,m=1.0;
40 1 : PetscScalar sigma,numer[2],denom[2];
41 1 : PetscBool terse;
42 :
43 1 : PetscFunctionBeginUser;
44 1 : PetscCall(SlepcInitialize(&argc,&argv,NULL,help));
45 :
46 1 : PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
47 1 : PetscCall(PetscOptionsGetReal(NULL,NULL,"-kappa",&kappa,NULL));
48 1 : PetscCall(PetscOptionsGetReal(NULL,NULL,"-mass",&m,NULL));
49 1 : sigma = kappa/m;
50 1 : PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Loaded vibrating string, n=%" PetscInt_FMT " kappa=%g m=%g\n\n",n,(double)kappa,(double)m));
51 :
52 : /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
53 : Build the problem matrices
54 : - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
55 :
56 : /* initialize matrices */
57 4 : for (i=0;i<NMAT;i++) {
58 3 : PetscCall(MatCreate(PETSC_COMM_WORLD,&A[i]));
59 3 : PetscCall(MatSetSizes(A[i],PETSC_DECIDE,PETSC_DECIDE,n,n));
60 3 : PetscCall(MatSetFromOptions(A[i]));
61 : }
62 1 : PetscCall(MatGetOwnershipRange(A[0],&Istart,&Iend));
63 :
64 : /* A0 */
65 101 : for (i=Istart;i<Iend;i++) {
66 100 : PetscCall(MatSetValue(A[0],i,i,(i==n-1)?1.0*n:2.0*n,INSERT_VALUES));
67 100 : if (i>0) PetscCall(MatSetValue(A[0],i,i-1,-1.0*n,INSERT_VALUES));
68 100 : if (i<n-1) PetscCall(MatSetValue(A[0],i,i+1,-1.0*n,INSERT_VALUES));
69 : }
70 :
71 : /* A1 */
72 101 : for (i=Istart;i<Iend;i++) {
73 100 : PetscCall(MatSetValue(A[1],i,i,(i==n-1)?2.0/(6.0*n):4.0/(6.0*n),INSERT_VALUES));
74 100 : if (i>0) PetscCall(MatSetValue(A[1],i,i-1,1.0/(6.0*n),INSERT_VALUES));
75 100 : if (i<n-1) PetscCall(MatSetValue(A[1],i,i+1,1.0/(6.0*n),INSERT_VALUES));
76 : }
77 :
78 : /* A2 */
79 1 : if (Istart<=n-1 && n-1<Iend) PetscCall(MatSetValue(A[2],n-1,n-1,kappa,INSERT_VALUES));
80 :
81 : /* assemble matrices */
82 4 : for (i=0;i<NMAT;i++) PetscCall(MatAssemblyBegin(A[i],MAT_FINAL_ASSEMBLY));
83 4 : for (i=0;i<NMAT;i++) PetscCall(MatAssemblyEnd(A[i],MAT_FINAL_ASSEMBLY));
84 :
85 : /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
86 : Create the problem functions
87 : - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
88 :
89 : /* f1=1 */
90 1 : PetscCall(FNCreate(PETSC_COMM_WORLD,&f[0]));
91 1 : PetscCall(FNSetType(f[0],FNRATIONAL));
92 1 : numer[0] = 1.0;
93 1 : PetscCall(FNRationalSetNumerator(f[0],1,numer));
94 :
95 : /* f2=-lambda */
96 1 : PetscCall(FNCreate(PETSC_COMM_WORLD,&f[1]));
97 1 : PetscCall(FNSetType(f[1],FNRATIONAL));
98 1 : numer[0] = -1.0; numer[1] = 0.0;
99 1 : PetscCall(FNRationalSetNumerator(f[1],2,numer));
100 :
101 : /* f3=lambda/(lambda-sigma)=1+sigma/(lambda-sigma) */
102 1 : PetscCall(FNCreate(PETSC_COMM_WORLD,&g));
103 1 : PetscCall(FNSetType(g,FNRATIONAL));
104 1 : numer[0] = sigma;
105 1 : denom[0] = 1.0; denom[1] = -sigma;
106 1 : PetscCall(FNRationalSetNumerator(g,1,numer));
107 1 : PetscCall(FNRationalSetDenominator(g,2,denom));
108 1 : PetscCall(FNCreate(PETSC_COMM_WORLD,&f[2]));
109 1 : PetscCall(FNSetType(f[2],FNCOMBINE));
110 1 : PetscCall(FNCombineSetChildren(f[2],FN_COMBINE_ADD,f[0],g));
111 :
112 : /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
113 : Create the eigensolver and solve the problem
114 : - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
115 :
116 1 : PetscCall(NEPCreate(PETSC_COMM_WORLD,&nep));
117 1 : PetscCall(NEPSetSplitOperator(nep,3,A,f,SUBSET_NONZERO_PATTERN));
118 1 : PetscCall(NEPSetProblemType(nep,NEP_RATIONAL));
119 1 : PetscCall(NEPSetFromOptions(nep));
120 1 : PetscCall(NEPSolve(nep));
121 :
122 : /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
123 : Display solution and clean up
124 : - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
125 :
126 : /* show detailed info unless -terse option is given by user */
127 1 : PetscCall(PetscOptionsHasName(NULL,NULL,"-terse",&terse));
128 1 : if (terse) PetscCall(NEPErrorView(nep,NEP_ERROR_RELATIVE,NULL));
129 : else {
130 0 : PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL));
131 0 : PetscCall(NEPConvergedReasonView(nep,PETSC_VIEWER_STDOUT_WORLD));
132 0 : PetscCall(NEPErrorView(nep,NEP_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD));
133 0 : PetscCall(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD));
134 : }
135 1 : PetscCall(NEPDestroy(&nep));
136 4 : for (i=0;i<NMAT;i++) {
137 3 : PetscCall(MatDestroy(&A[i]));
138 3 : PetscCall(FNDestroy(&f[i]));
139 : }
140 1 : PetscCall(FNDestroy(&g));
141 1 : PetscCall(SlepcFinalize());
142 : return 0;
143 : }
144 :
145 : /*TEST
146 :
147 : test:
148 : suffix: 1
149 : args: -nep_type nleigs -rg_type interval -rg_interval_endpoints 4,700,-.1,.1 -nep_nev 8 -nep_target 5 -terse
150 : filter: sed -e "s/[+-]0\.0*i//g"
151 : requires: !single
152 :
153 : TEST*/
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