Actual source code: ex22.c

slepc-3.21.1 2024-04-26
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```  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.
8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
9: */

11: static char help[] = "Delay differential equation.\n\n"
12:   "The command line options are:\n"
13:   "  -n <n>, where <n> = number of grid subdivisions.\n"
14:   "  -tau <tau>, where <tau> is the delay parameter.\n\n";

16: /*
17:    Solve parabolic partial differential equation with time delay tau

19:             u_t = u_xx + a*u(t) + b*u(t-tau)
20:             u(0,t) = u(pi,t) = 0

22:    with a = 20 and b(x) = -4.1+x*(1-exp(x-pi)).

24:    Discretization leads to a DDE of dimension n

26:             -u' = A*u(t) + B*u(t-tau)

28:    which results in the nonlinear eigenproblem

30:             (-lambda*I + A + exp(-tau*lambda)*B)*u = 0
31: */

33: #include <slepcnep.h>

35: int main(int argc,char **argv)
36: {
37:   NEP            nep;             /* nonlinear eigensolver context */
38:   Mat            Id,A,B;          /* problem matrices */
39:   FN             f1,f2,f3;        /* functions to define the nonlinear operator */
40:   Mat            mats[3];
41:   FN             funs[3];
42:   PetscScalar    coeffs[2],b;
43:   PetscInt       n=128,nev,Istart,Iend,i;
44:   PetscReal      tau=0.001,h,a=20,xi;
45:   PetscBool      terse;

47:   PetscFunctionBeginUser;
48:   PetscCall(SlepcInitialize(&argc,&argv,(char*)0,help));
49:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
50:   PetscCall(PetscOptionsGetReal(NULL,NULL,"-tau",&tau,NULL));
51:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\n1-D Delay Eigenproblem, n=%" PetscInt_FMT ", tau=%g\n\n",n,(double)tau));
52:   h = PETSC_PI/(PetscReal)(n+1);

54:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
55:      Create nonlinear eigensolver context
56:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

58:   PetscCall(NEPCreate(PETSC_COMM_WORLD,&nep));

60:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
61:      Create problem matrices and coefficient functions. Pass them to NEP
62:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

64:   /*
65:      Identity matrix
66:   */
67:   PetscCall(MatCreateConstantDiagonal(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,n,n,1.0,&Id));
68:   PetscCall(MatSetOption(Id,MAT_HERMITIAN,PETSC_TRUE));

70:   /*
71:      A = 1/h^2*tridiag(1,-2,1) + a*I
72:   */
73:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
74:   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n));
75:   PetscCall(MatSetFromOptions(A));
76:   PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
77:   for (i=Istart;i<Iend;i++) {
78:     if (i>0) PetscCall(MatSetValue(A,i,i-1,1.0/(h*h),INSERT_VALUES));
79:     if (i<n-1) PetscCall(MatSetValue(A,i,i+1,1.0/(h*h),INSERT_VALUES));
80:     PetscCall(MatSetValue(A,i,i,-2.0/(h*h)+a,INSERT_VALUES));
81:   }
82:   PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
83:   PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));
84:   PetscCall(MatSetOption(A,MAT_HERMITIAN,PETSC_TRUE));

86:   /*
87:      B = diag(b(xi))
88:   */
89:   PetscCall(MatCreate(PETSC_COMM_WORLD,&B));
90:   PetscCall(MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,n,n));
91:   PetscCall(MatSetFromOptions(B));
92:   PetscCall(MatGetOwnershipRange(B,&Istart,&Iend));
93:   for (i=Istart;i<Iend;i++) {
94:     xi = (i+1)*h;
95:     b = -4.1+xi*(1.0-PetscExpReal(xi-PETSC_PI));
96:     PetscCall(MatSetValue(B,i,i,b,INSERT_VALUES));
97:   }
98:   PetscCall(MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY));
99:   PetscCall(MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY));
100:   PetscCall(MatSetOption(B,MAT_HERMITIAN,PETSC_TRUE));

102:   /*
103:      Functions: f1=-lambda, f2=1.0, f3=exp(-tau*lambda)
104:   */
105:   PetscCall(FNCreate(PETSC_COMM_WORLD,&f1));
106:   PetscCall(FNSetType(f1,FNRATIONAL));
107:   coeffs[0] = -1.0; coeffs[1] = 0.0;
108:   PetscCall(FNRationalSetNumerator(f1,2,coeffs));

110:   PetscCall(FNCreate(PETSC_COMM_WORLD,&f2));
111:   PetscCall(FNSetType(f2,FNRATIONAL));
112:   coeffs[0] = 1.0;
113:   PetscCall(FNRationalSetNumerator(f2,1,coeffs));

115:   PetscCall(FNCreate(PETSC_COMM_WORLD,&f3));
116:   PetscCall(FNSetType(f3,FNEXP));
117:   PetscCall(FNSetScale(f3,-tau,1.0));

119:   /*
120:      Set the split operator. Note that A is passed first so that
121:      SUBSET_NONZERO_PATTERN can be used
122:   */
123:   mats[0] = A;  funs[0] = f2;
124:   mats[1] = Id; funs[1] = f1;
125:   mats[2] = B;  funs[2] = f3;
126:   PetscCall(NEPSetSplitOperator(nep,3,mats,funs,SUBSET_NONZERO_PATTERN));

128:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
129:              Customize nonlinear solver; set runtime options
130:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

132:   PetscCall(NEPSetTolerances(nep,1e-9,PETSC_DEFAULT));
133:   PetscCall(NEPSetDimensions(nep,1,PETSC_DEFAULT,PETSC_DEFAULT));
134:   PetscCall(NEPRIISetLagPreconditioner(nep,0));

136:   /*
137:      Set solver parameters at runtime
138:   */
139:   PetscCall(NEPSetFromOptions(nep));

141:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
142:                       Solve the eigensystem
143:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

145:   PetscCall(NEPSolve(nep));
146:   PetscCall(NEPGetDimensions(nep,&nev,NULL,NULL));
147:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %" PetscInt_FMT "\n",nev));

149:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
150:                     Display solution and clean up
151:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

153:   /* show detailed info unless -terse option is given by user */
154:   PetscCall(PetscOptionsHasName(NULL,NULL,"-terse",&terse));
155:   if (terse) PetscCall(NEPErrorView(nep,NEP_ERROR_RELATIVE,NULL));
156:   else {
157:     PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL));
158:     PetscCall(NEPConvergedReasonView(nep,PETSC_VIEWER_STDOUT_WORLD));
159:     PetscCall(NEPErrorView(nep,NEP_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD));
160:     PetscCall(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD));
161:   }
162:   PetscCall(NEPDestroy(&nep));
163:   PetscCall(MatDestroy(&Id));
164:   PetscCall(MatDestroy(&A));
165:   PetscCall(MatDestroy(&B));
166:   PetscCall(FNDestroy(&f1));
167:   PetscCall(FNDestroy(&f2));
168:   PetscCall(FNDestroy(&f3));
169:   PetscCall(SlepcFinalize());
170:   return 0;
171: }

173: /*TEST

175:    testset:
176:       suffix: 1
177:       args: -nep_type {{rii slp narnoldi}} -terse
178:       filter: sed -e "s/[+-]0\.0*i//g"
179:       requires: !single

181:    test:
182:       suffix: 1_ciss
183:       args: -nep_type ciss -nep_ciss_extraction {{ritz hankel caa}} -rg_type ellipse -rg_ellipse_center 10 -rg_ellipse_radius 9.5 -nep_ncv 24 -terse
184:       requires: complex !single

186:    test:
187:       suffix: 2
188:       args: -nep_type interpol -nep_interpol_pep_extract {{none norm residual}} -rg_type interval -rg_interval_endpoints 5,20,-.1,.1 -nep_nev 3 -nep_target 5 -terse
189:       filter: sed -e "s/[+-]0\.0*i//g"
190:       requires: !single

192:    testset:
193:       args: -n 512 -nep_target 10 -nep_nev 3 -terse
194:       filter: sed -e "s/[+-]0\.0*i//g"
195:       requires: !single
196:       output_file: output/ex22_3.out
197:       test:
198:          suffix: 3
199:          args: -nep_type {{rii slp narnoldi}}
200:       test:
201:          suffix: 3_simpleu
202:          args: -nep_type {{rii slp narnoldi}} -nep_deflation_simpleu
203:       test:
204:          suffix: 3_slp_thres
205:          args: -nep_type slp -nep_slp_deflation_threshold 1e-8
206:       test:
207:          suffix: 3_rii_thres
208:          args: -nep_type rii -nep_rii_deflation_threshold 1e-8

210:    test:
211:       suffix: 4
212:       args: -nep_type interpol -rg_type interval -rg_interval_endpoints 5,20,-.1,.1 -nep_nev 3 -nep_target 5 -terse -nep_monitor draw::draw_lg
213:       filter: sed -e "s/[+-]0\.0*i//g"
214:       requires: x !single
215:       output_file: output/ex22_2.out

217: TEST*/
```