1: static char help[] = "Solves DAE with integrator only on non-algebraic terms \n";

  3: #include <petscts.h>

  5: /*
  6:         \dot{U} = f(U,V)
  7:         F(U,V)  = 0

  9:     Same as ex6.c and ex7.c except calls the ARKIMEX integrator on the entire DAE
 10: */


 15: /*
 16:    f(U,V) = U + V

 18: */
 19: PetscErrorCode f(PetscReal t,Vec U,Vec V,Vec F)
 20: {

 24:   VecWAXPY(F,1.0,U,V);
 25:   return(0);
 26: }

 30: /*
 31:    F(U,V) = U - V

 33: */
 34: PetscErrorCode F(PetscReal t,Vec U,Vec V,Vec F)
 35: {

 39:   VecWAXPY(F,-1.0,V,U);
 40:   return(0);
 41: }


 44: typedef struct {
 45:   Vec            U,V;
 46:   Vec            UF,VF;
 47:   VecScatter     scatterU,scatterV;
 48:   PetscErrorCode (*f)(PetscReal,Vec,Vec,Vec);
 49:   PetscErrorCode (*F)(PetscReal,Vec,Vec,Vec);
 50: } AppCtx;

 52: extern PetscErrorCode TSFunctionRHS(TS,PetscReal,Vec,Vec,void*);
 53: extern PetscErrorCode TSFunctionI(TS,PetscReal,Vec,Vec,Vec,void*);

 57: int main(int argc,char **argv)
 58: {
 60:   AppCtx         ctx;
 61:   TS             ts;
 62:   Vec            tsrhs,UV;
 63:   IS             is;
 64:   PetscInt       I;
 65:   PetscMPIInt    rank;


 68:   PetscInitialize(&argc,&argv,(char*)0,help);
 69:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 70:   TSCreate(PETSC_COMM_WORLD,&ts);
 71:   TSSetProblemType(ts,TS_NONLINEAR);
 72:   TSSetType(ts,TSROSW);
 73:   TSSetFromOptions(ts);
 74:   VecCreateMPI(PETSC_COMM_WORLD,2,PETSC_DETERMINE,&tsrhs);
 75:   VecCreateMPI(PETSC_COMM_WORLD,2,PETSC_DETERMINE,&UV);
 76:   TSSetRHSFunction(ts,tsrhs,TSFunctionRHS,&ctx);
 77:   TSSetIFunction(ts,NULL,TSFunctionI,&ctx);
 78:   ctx.f = f;
 79:   ctx.F = F;

 81:   VecCreateMPI(PETSC_COMM_WORLD,1,PETSC_DETERMINE,&ctx.U);
 82:   VecCreateMPI(PETSC_COMM_WORLD,1,PETSC_DETERMINE,&ctx.V);
 83:   VecCreateMPI(PETSC_COMM_WORLD,1,PETSC_DETERMINE,&ctx.UF);
 84:   VecCreateMPI(PETSC_COMM_WORLD,1,PETSC_DETERMINE,&ctx.VF);
 85:   I    = 2*rank;
 86:   ISCreateGeneral(PETSC_COMM_WORLD,1,&I,PETSC_COPY_VALUES,&is);
 87:   VecScatterCreate(ctx.U,NULL,UV,is,&ctx.scatterU);
 88:   ISDestroy(&is);
 89:   I    = 2*rank + 1;
 90:   ISCreateGeneral(PETSC_COMM_WORLD,1,&I,PETSC_COPY_VALUES,&is);
 91:   VecScatterCreate(ctx.V,NULL,UV,is,&ctx.scatterV);
 92:   ISDestroy(&is);

 94:   VecSet(UV,1.0);
 95:   TSSolve(ts,UV);
 96:   VecDestroy(&tsrhs);
 97:   VecDestroy(&UV);
 98:   VecDestroy(&ctx.U);
 99:   VecDestroy(&ctx.V);
100:   VecDestroy(&ctx.UF);
101:   VecDestroy(&ctx.VF);
102:   VecScatterDestroy(&ctx.scatterU);
103:   VecScatterDestroy(&ctx.scatterV);
104:   TSDestroy(&ts);
105:   PetscFinalize();
106:   return 0;
107: }

111: /*
112:    Defines the RHS function that is passed to the time-integrator. 

114: */
115: PetscErrorCode TSFunctionRHS(TS ts,PetscReal t,Vec UV,Vec F,void *actx)
116: {
117:   AppCtx         *ctx = (AppCtx*)actx;

121:   VecSet(F,0.0);
122:   VecScatterBegin(ctx->scatterU,UV,ctx->U,INSERT_VALUES,SCATTER_REVERSE);
123:   VecScatterEnd(ctx->scatterU,UV,ctx->U,INSERT_VALUES,SCATTER_REVERSE);
124:   VecScatterBegin(ctx->scatterV,UV,ctx->V,INSERT_VALUES,SCATTER_REVERSE);
125:   VecScatterEnd(ctx->scatterV,UV,ctx->V,INSERT_VALUES,SCATTER_REVERSE);
126:   (*ctx->f)(t,ctx->U,ctx->V,ctx->UF);
127:   VecScatterBegin(ctx->scatterU,ctx->UF,F,INSERT_VALUES,SCATTER_FORWARD);
128:   VecScatterEnd(ctx->scatterU,ctx->UF,F,INSERT_VALUES,SCATTER_FORWARD);
129:   return(0);
130: }

134: /*
135:    Defines the nonlinear function that is passed to the time-integrator

137: */
138: PetscErrorCode TSFunctionI(TS ts,PetscReal t,Vec UV,Vec UVdot,Vec F,void *actx)
139: {
140:   AppCtx         *ctx = (AppCtx*)actx;

144:   VecCopy(UVdot,F);
145:   VecScatterBegin(ctx->scatterU,UV,ctx->U,INSERT_VALUES,SCATTER_REVERSE);
146:   VecScatterEnd(ctx->scatterU,UV,ctx->U,INSERT_VALUES,SCATTER_REVERSE);
147:   VecScatterBegin(ctx->scatterV,UV,ctx->V,INSERT_VALUES,SCATTER_REVERSE);
148:   VecScatterEnd(ctx->scatterV,UV,ctx->V,INSERT_VALUES,SCATTER_REVERSE);
149:   (*ctx->F)(t,ctx->U,ctx->V,ctx->VF);
150:   VecScatterBegin(ctx->scatterV,ctx->VF,F,INSERT_VALUES,SCATTER_FORWARD);
151:   VecScatterEnd(ctx->scatterV,ctx->VF,F,INSERT_VALUES,SCATTER_FORWARD);
152:   return(0);
153: }