Actual source code: test3.c

slepc-3.18.3 2023-03-24
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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.
  7:    SLEPc is distributed under a 2-clause BSD license (see LICENSE).
  8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  9: */

 11: static char help[] = "Test the SLP solver with a user-provided EPS.\n\n"
 12:   "This is a simplified version of ex20.\n"
 13:   "The command line options are:\n"
 14:   "  -n <n>, where <n> = number of grid subdivisions.\n";

 16: /*
 17:    Solve 1-D PDE
 18:             -u'' = lambda*u
 19:    on [0,1] subject to
 20:             u(0)=0, u'(1)=u(1)*lambda*kappa/(kappa-lambda)
 21: */

 23: #include <slepcnep.h>

 25: /*
 26:    User-defined routines
 27: */
 28: PetscErrorCode FormFunction(NEP,PetscScalar,Mat,Mat,void*);
 29: PetscErrorCode FormJacobian(NEP,PetscScalar,Mat,void*);

 31: /*
 32:    User-defined application context
 33: */
 34: typedef struct {
 35:   PetscScalar kappa;   /* ratio between stiffness of spring and attached mass */
 36:   PetscReal   h;       /* mesh spacing */
 37: } ApplicationCtx;

 39: int main(int argc,char **argv)
 40: {
 41:   NEP            nep;
 42:   EPS            eps;
 43:   KSP            ksp;
 44:   PC             pc;
 45:   Mat            F,J;
 46:   ApplicationCtx ctx;
 47:   PetscInt       n=128;
 48:   PetscReal      deftol;
 49:   PetscBool      terse,flag,ts;

 52:   SlepcInitialize(&argc,&argv,(char*)0,help);
 53:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
 54:   PetscPrintf(PETSC_COMM_WORLD,"\n1-D Nonlinear Eigenproblem, n=%" PetscInt_FMT "\n\n",n);
 55:   ctx.h = 1.0/(PetscReal)n;
 56:   ctx.kappa = 1.0;

 58:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 59:         Create a standalone EPS with appropriate settings
 60:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 62:   EPSCreate(PETSC_COMM_WORLD,&eps);
 63:   EPSSetType(eps,EPSGD);
 64:   EPSSetFromOptions(eps);

 66:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 67:         Create a standalone KSP with appropriate settings
 68:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 70:   KSPCreate(PETSC_COMM_WORLD,&ksp);
 71:   KSPSetType(ksp,KSPBCGS);
 72:   KSPGetPC(ksp,&pc);
 73:   PCSetType(pc,PCBJACOBI);
 74:   KSPSetFromOptions(ksp);

 76:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 77:                Prepare nonlinear eigensolver context
 78:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 80:   NEPCreate(PETSC_COMM_WORLD,&nep);

 82:   /* Create Function and Jacobian matrices; set evaluation routines */
 83:   MatCreate(PETSC_COMM_WORLD,&F);
 84:   MatSetSizes(F,PETSC_DECIDE,PETSC_DECIDE,n,n);
 85:   MatSetFromOptions(F);
 86:   MatSeqAIJSetPreallocation(F,3,NULL);
 87:   MatMPIAIJSetPreallocation(F,3,NULL,1,NULL);
 88:   MatSetUp(F);
 89:   NEPSetFunction(nep,F,F,FormFunction,&ctx);

 91:   MatCreate(PETSC_COMM_WORLD,&J);
 92:   MatSetSizes(J,PETSC_DECIDE,PETSC_DECIDE,n,n);
 93:   MatSetFromOptions(J);
 94:   MatSeqAIJSetPreallocation(J,3,NULL);
 95:   MatMPIAIJSetPreallocation(F,3,NULL,1,NULL);
 96:   MatSetUp(J);
 97:   NEPSetJacobian(nep,J,FormJacobian,&ctx);

 99:   /* Set options */
100:   NEPSetType(nep,NEPSLP);
101:   NEPSLPSetEPS(nep,eps);
102:   NEPSLPSetKSP(nep,ksp);
103:   NEPSetFromOptions(nep);

105:   /* Print some options */
106:   PetscObjectTypeCompare((PetscObject)nep,NEPSLP,&flag);
107:   if (flag) {
108:     NEPGetTwoSided(nep,&ts);
109:     if (ts) {
110:       NEPSLPGetDeflationThreshold(nep,&deftol);
111:       PetscPrintf(PETSC_COMM_WORLD," Two-sided solve with deflation threshold=%g\n",(double)deftol);
112:     }
113:   }

115:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
116:                       Solve the eigensystem
117:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

119:   NEPSolve(nep);

121:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
122:                     Display solution and clean up
123:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

125:   /* show detailed info unless -terse option is given by user */
126:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
127:   if (terse) NEPErrorView(nep,NEP_ERROR_RELATIVE,NULL);
128:   else {
129:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
130:     NEPConvergedReasonView(nep,PETSC_VIEWER_STDOUT_WORLD);
131:     NEPErrorView(nep,NEP_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
132:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
133:   }

135:   NEPDestroy(&nep);
136:   EPSDestroy(&eps);
137:   KSPDestroy(&ksp);
138:   MatDestroy(&F);
139:   MatDestroy(&J);
140:   SlepcFinalize();
141:   return 0;
142: }

144: /* ------------------------------------------------------------------- */
145: /*
146:    FormFunction - Computes Function matrix  T(lambda)

148:    Input Parameters:
149: .  nep    - the NEP context
150: .  lambda - the scalar argument
151: .  ctx    - optional user-defined context, as set by NEPSetFunction()

153:    Output Parameters:
154: .  fun - Function matrix
155: .  B   - optionally different preconditioning matrix
156: */
157: PetscErrorCode FormFunction(NEP nep,PetscScalar lambda,Mat fun,Mat B,void *ctx)
158: {
159:   ApplicationCtx *user = (ApplicationCtx*)ctx;
160:   PetscScalar    A[3],c,d;
161:   PetscReal      h;
162:   PetscInt       i,n,j[3],Istart,Iend;
163:   PetscBool      FirstBlock=PETSC_FALSE,LastBlock=PETSC_FALSE;

166:   /*
167:      Compute Function entries and insert into matrix
168:   */
169:   MatGetSize(fun,&n,NULL);
170:   MatGetOwnershipRange(fun,&Istart,&Iend);
171:   if (Istart==0) FirstBlock=PETSC_TRUE;
172:   if (Iend==n) LastBlock=PETSC_TRUE;
173:   h = user->h;
174:   c = user->kappa/(lambda-user->kappa);
175:   d = n;

177:   /*
178:      Interior grid points
179:   */
180:   for (i=(FirstBlock? Istart+1: Istart);i<(LastBlock? Iend-1: Iend);i++) {
181:     j[0] = i-1; j[1] = i; j[2] = i+1;
182:     A[0] = A[2] = -d-lambda*h/6.0; A[1] = 2.0*(d-lambda*h/3.0);
183:     MatSetValues(fun,1,&i,3,j,A,INSERT_VALUES);
184:   }

186:   /*
187:      Boundary points
188:   */
189:   if (FirstBlock) {
190:     i = 0;
191:     j[0] = 0; j[1] = 1;
192:     A[0] = 2.0*(d-lambda*h/3.0); A[1] = -d-lambda*h/6.0;
193:     MatSetValues(fun,1,&i,2,j,A,INSERT_VALUES);
194:   }

196:   if (LastBlock) {
197:     i = n-1;
198:     j[0] = n-2; j[1] = n-1;
199:     A[0] = -d-lambda*h/6.0; A[1] = d-lambda*h/3.0+lambda*c;
200:     MatSetValues(fun,1,&i,2,j,A,INSERT_VALUES);
201:   }

203:   /*
204:      Assemble matrix
205:   */
206:   MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY);
207:   MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY);
208:   if (fun != B) {
209:     MatAssemblyBegin(fun,MAT_FINAL_ASSEMBLY);
210:     MatAssemblyEnd(fun,MAT_FINAL_ASSEMBLY);
211:   }
212:   return 0;
213: }

215: /* ------------------------------------------------------------------- */
216: /*
217:    FormJacobian - Computes Jacobian matrix  T'(lambda)

219:    Input Parameters:
220: .  nep    - the NEP context
221: .  lambda - the scalar argument
222: .  ctx    - optional user-defined context, as set by NEPSetJacobian()

224:    Output Parameters:
225: .  jac - Jacobian matrix
226: .  B   - optionally different preconditioning matrix
227: */
228: PetscErrorCode FormJacobian(NEP nep,PetscScalar lambda,Mat jac,void *ctx)
229: {
230:   ApplicationCtx *user = (ApplicationCtx*)ctx;
231:   PetscScalar    A[3],c;
232:   PetscReal      h;
233:   PetscInt       i,n,j[3],Istart,Iend;
234:   PetscBool      FirstBlock=PETSC_FALSE,LastBlock=PETSC_FALSE;

237:   /*
238:      Compute Jacobian entries and insert into matrix
239:   */
240:   MatGetSize(jac,&n,NULL);
241:   MatGetOwnershipRange(jac,&Istart,&Iend);
242:   if (Istart==0) FirstBlock=PETSC_TRUE;
243:   if (Iend==n) LastBlock=PETSC_TRUE;
244:   h = user->h;
245:   c = user->kappa/(lambda-user->kappa);

247:   /*
248:      Interior grid points
249:   */
250:   for (i=(FirstBlock? Istart+1: Istart);i<(LastBlock? Iend-1: Iend);i++) {
251:     j[0] = i-1; j[1] = i; j[2] = i+1;
252:     A[0] = A[2] = -h/6.0; A[1] = -2.0*h/3.0;
253:     MatSetValues(jac,1,&i,3,j,A,INSERT_VALUES);
254:   }

256:   /*
257:      Boundary points
258:   */
259:   if (FirstBlock) {
260:     i = 0;
261:     j[0] = 0; j[1] = 1;
262:     A[0] = -2.0*h/3.0; A[1] = -h/6.0;
263:     MatSetValues(jac,1,&i,2,j,A,INSERT_VALUES);
264:   }

266:   if (LastBlock) {
267:     i = n-1;
268:     j[0] = n-2; j[1] = n-1;
269:     A[0] = -h/6.0; A[1] = -h/3.0-c*c;
270:     MatSetValues(jac,1,&i,2,j,A,INSERT_VALUES);
271:   }

273:   /*
274:      Assemble matrix
275:   */
276:   MatAssemblyBegin(jac,MAT_FINAL_ASSEMBLY);
277:   MatAssemblyEnd(jac,MAT_FINAL_ASSEMBLY);
278:   return 0;
279: }

281: /*TEST

283:    test:
284:       args: -nep_target 21 -terse
285:       requires: !single
286:       test:
287:          suffix: 1
288:       test:
289:          suffix: 1_ts
290:          args: -nep_two_sided

292: TEST*/