Actual source code: ex21.c
1: /*$Id: ex21.c,v 1.11 2001/08/07 03:04:16 balay Exp $*/
3: static char help[] = "Solves PDE optimization problem.nn";
5: #include petscda.h
6: #include petscpf.h
7: #include petscsnes.h
9: /*
11: w - design variables (what we change to get an optimal solution)
12: u - state variables (i.e. the PDE solution)
13: lambda - the Lagrange multipliers
15: U = (w u lambda)
17: fu, fw, flambda contain the gradient of L(w,u,lambda)
19: FU = (fw fu flambda)
21: In this example the PDE is
22: Uxx = 2,
23: u(0) = w(0), thus this is the free parameter
24: u(1) = 0
25: the function we wish to minimize is
26: integral u^{2}
28: The exact solution for u is given by u(x) = x*x - 1.25*x + .25
30: Use the usual centered finite differences.
32: Note we treat the problem as non-linear though it happens to be linear
34: See ex22.c for the same code, but that interlaces the u and the lambda
36: */
38: typedef struct {
39: DA da1,da2;
40: int nredundant;
41: VecPack packer;
42: PetscViewer u_viewer,lambda_viewer;
43: PetscViewer fu_viewer,flambda_viewer;
44: } UserCtx;
46: extern int FormFunction(SNES,Vec,Vec,void*);
47: extern int Monitor(SNES,int,PetscReal,void*);
50: #undef __FUNCT__
52: int main(int argc,char **argv)
53: {
54: int ierr,its;
55: Vec U,FU;
56: SNES snes;
57: UserCtx user;
59: PetscInitialize(&argc,&argv,(char*)0,help);
61: /* Create a global vector that includes a single redundant array and two da arrays */
62: VecPackCreate(PETSC_COMM_WORLD,&user.packer);
63: user.nredundant = 1;
64: VecPackAddArray(user.packer,user.nredundant);
65: DACreate1d(PETSC_COMM_WORLD,DA_NONPERIODIC,-5,1,1,PETSC_NULL,&user.da1);
66: VecPackAddDA(user.packer,user.da1);
67: DACreate1d(PETSC_COMM_WORLD,DA_NONPERIODIC,-5,1,1,PETSC_NULL,&user.da2);
68: VecPackAddDA(user.packer,user.da2);
69: VecPackCreateGlobalVector(user.packer,&U);
70: VecDuplicate(U,&FU);
72: /* create graphics windows */
73: PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"u - state variables",-1,-1,-1,-1,&user.u_viewer);
74: PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"lambda - Lagrange multipliers",-1,-1,-1,-1,&user.lambda_viewer);
75: PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"fu - derivate w.r.t. state variables",-1,-1,-1,-1,&user.fu_viewer);
76: PetscViewerDrawOpen(PETSC_COMM_WORLD,0,"flambda - derivate w.r.t. Lagrange multipliers",-1,-1,-1,-1,&user.flambda_viewer);
79: /* create nonlinear solver */
80: SNESCreate(PETSC_COMM_WORLD,&snes);
81: SNESSetFunction(snes,FU,FormFunction,&user);
82: SNESSetFromOptions(snes);
83: SNESSetMonitor(snes,Monitor,&user,0);
84: SNESSolve(snes,U,&its);
85: SNESDestroy(snes);
87: DADestroy(user.da1);
88: DADestroy(user.da2);
89: VecPackDestroy(user.packer);
90: VecDestroy(U);
91: VecDestroy(FU);
92: PetscViewerDestroy(user.u_viewer);
93: PetscViewerDestroy(user.lambda_viewer);
94: PetscViewerDestroy(user.fu_viewer);
95: PetscViewerDestroy(user.flambda_viewer);
96: PetscFinalize();
97: return 0;
98: }
99:
100: /*
101: Evaluates FU = Gradiant(L(w,u,lambda))
103: */
104: int FormFunction(SNES snes,Vec U,Vec FU,void* dummy)
105: {
106: UserCtx *user = (UserCtx*)dummy;
107: int ierr,xs,xm,i,N;
108: PetscScalar *u,*lambda,*w,*fu,*fw,*flambda,d,h;
109: Vec vu,vlambda,vfu,vflambda;
112: VecPackGetLocalVectors(user->packer,&w,&vu,&vlambda);
113: VecPackGetLocalVectors(user->packer,&fw,&vfu,&vflambda);
114: VecPackScatter(user->packer,U,w,vu,vlambda);
116: DAGetCorners(user->da1,&xs,PETSC_NULL,PETSC_NULL,&xm,PETSC_NULL,PETSC_NULL);
117: DAGetInfo(user->da1,0,&N,0,0,0,0,0,0,0,0,0);
118: DAVecGetArray(user->da1,vu,(void**)&u);
119: DAVecGetArray(user->da1,vfu,(void**)&fu);
120: DAVecGetArray(user->da1,vlambda,(void**)&lambda);
121: DAVecGetArray(user->da1,vflambda,(void**)&flambda);
122: d = (N-1.0);
123: h = 1.0/d;
125: /* derivative of L() w.r.t. w */
126: if (xs == 0) { /* only first processor computes this */
127: fw[0] = -2.*d*lambda[0];
128: }
130: /* derivative of L() w.r.t. u */
131: for (i=xs; i<xs+xm; i++) {
132: if (i == 0) flambda[0] = h*u[0] + 2.*d*lambda[0] - d*lambda[1];
133: else if (i == 1) flambda[1] = 2.*h*u[1] + 2.*d*lambda[1] - d*lambda[2];
134: else if (i == N-1) flambda[N-1] = h*u[N-1] + 2.*d*lambda[N-1] - d*lambda[N-2];
135: else if (i == N-2) flambda[N-2] = 2.*h*u[N-2] + 2.*d*lambda[N-2] - d*lambda[N-3];
136: else flambda[i] = 2.*h*u[i] - d*(lambda[i+1] - 2.0*lambda[i] + lambda[i-1]);
137: }
139: /* derivative of L() w.r.t. lambda */
140: for (i=xs; i<xs+xm; i++) {
141: if (i == 0) fu[0] = 2.0*d*(u[0] - w[0]);
142: else if (i == N-1) fu[N-1] = 2.0*d*u[N-1];
143: else fu[i] = -(d*(u[i+1] - 2.0*u[i] + u[i-1]) - 2.0*h);
144: }
146: DAVecRestoreArray(user->da1,vu,(void**)&u);
147: DAVecRestoreArray(user->da1,vfu,(void**)&fu);
148: DAVecRestoreArray(user->da1,vlambda,(void**)&lambda);
149: DAVecRestoreArray(user->da1,vflambda,(void**)&flambda);
151: VecPackGather(user->packer,FU,fw,vfu,vflambda);
152: VecPackRestoreLocalVectors(user->packer,&w,&vu,&vlambda);
153: VecPackRestoreLocalVectors(user->packer,&fw,&vfu,&vflambda);
154: return(0);
155: }
157: int Monitor(SNES snes,int its,PetscReal rnorm,void *dummy)
158: {
159: UserCtx *user = (UserCtx*)dummy;
160: int ierr;
161: PetscScalar *w;
162: Vec u,lambda,U,F;
165: SNESGetSolution(snes,&U);
166: VecPackGetAccess(user->packer,U,&w,&u,&lambda);
167: VecView(u,user->u_viewer);
168: VecView(lambda,user->lambda_viewer);
169: VecPackRestoreAccess(user->packer,U,&w,&u,&lambda);
171: SNESGetFunction(snes,&F,0,0);
172: VecPackGetAccess(user->packer,F,&w,&u,&lambda);
173: VecView(u,user->fu_viewer);
174: VecView(lambda,user->flambda_viewer);
175: VecPackRestoreAccess(user->packer,F,&w,&u,&lambda);
176: return(0);
177: }