PetscErrorCode FormJacobian(SNES snes,Vec X,Mat *J,Mat *B,MatStructure *flag,void *ptr)
{
AppCtx *user = (AppCtx *) ptr;
PetscErrorCode ierr;
KSP ksp;
PC pc;
PetscBool ismg;
*flag = SAME_NONZERO_PATTERN;
ierr = FormJacobian_Grid(user,&user->fine,X,J,B);CHKERRQ(ierr);
/* create coarse grid jacobian for preconditioner */
ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr);
ierr = PetscObjectTypeCompare((PetscObject)pc,PCMG,&ismg);CHKERRQ(ierr);
if (ismg) {
ierr = KSPSetOperators(user->ksp_fine,user->fine.J,user->fine.J,SAME_NONZERO_PATTERN);CHKERRQ(ierr);
/* restrict X to coarse grid */
ierr = MatMult(user->R,X,user->coarse.x);CHKERRQ(ierr);
ierr = VecPointwiseMult(user->coarse.x,user->coarse.x,user->Rscale);CHKERRQ(ierr);
/* form Jacobian on coarse grid */
if (user->redundant_build) {
/* get copy of coarse X onto each processor */
ierr = VecScatterBegin(user->tolocalall,user->coarse.x,user->localall,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
ierr = VecScatterEnd(user->tolocalall,user->coarse.x,user->localall,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
ierr = FormJacobian_Coarse(user,&user->coarse,user->localall,&user->coarse.J,&user->coarse.J);CHKERRQ(ierr);
} else {
/* coarse grid Jacobian computed in parallel */
ierr = FormJacobian_Grid(user,&user->coarse,user->coarse.x,&user->coarse.J,&user->coarse.J);CHKERRQ(ierr);
}
ierr = KSPSetOperators(user->ksp_coarse,user->coarse.J,user->coarse.J,SAME_NONZERO_PATTERN);CHKERRQ(ierr);
}
return 0;
}
int main(int argc,char **argv)
{
PetscErrorCode ierr;
PetscInt its,n,Nx=PETSC_DECIDE,Ny=PETSC_DECIDE,nlocal;
PetscMPIInt size;
PetscScalar one = 1.0;
PetscInt mx,my;
Mat A;
GridCtx fine_ctx;
KSP ksp;
PetscBool flg;
ierr = PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
/* set up discretization matrix for fine grid */
fine_ctx.mx = 9; fine_ctx.my = 9;
ierr = PetscOptionsGetInt(NULL,NULL,"-mx",&mx,&flg);CHKERRQ(ierr);
if (flg) fine_ctx.mx = mx;
ierr = PetscOptionsGetInt(NULL,NULL,"-my",&my,&flg);CHKERRQ(ierr);
if (flg) fine_ctx.my = my;
ierr = PetscPrintf(PETSC_COMM_WORLD,"Fine grid size %D by %D\n",fine_ctx.mx,fine_ctx.my);CHKERRQ(ierr);
n = fine_ctx.mx*fine_ctx.my;
MPI_Comm_size(PETSC_COMM_WORLD,&size);
ierr = PetscOptionsGetInt(NULL,NULL,"-Nx",&Nx,NULL);CHKERRQ(ierr);
ierr = PetscOptionsGetInt(NULL,NULL,"-Ny",&Ny,NULL);CHKERRQ(ierr);
/* Set up distributed array for fine grid */
ierr = DMDACreate2d(PETSC_COMM_WORLD, DM_BOUNDARY_NONE, DM_BOUNDARY_NONE,DMDA_STENCIL_STAR,fine_ctx.mx,
fine_ctx.my,Nx,Ny,1,1,NULL,NULL,&fine_ctx.da);CHKERRQ(ierr);
ierr = DMCreateGlobalVector(fine_ctx.da,&fine_ctx.x);CHKERRQ(ierr);
ierr = VecDuplicate(fine_ctx.x,&fine_ctx.b);CHKERRQ(ierr);
ierr = VecGetLocalSize(fine_ctx.x,&nlocal);CHKERRQ(ierr);
ierr = DMCreateLocalVector(fine_ctx.da,&fine_ctx.localX);CHKERRQ(ierr);
ierr = VecDuplicate(fine_ctx.localX,&fine_ctx.localF);CHKERRQ(ierr);
ierr = MatCreateAIJ(PETSC_COMM_WORLD,nlocal,nlocal,n,n,5,NULL,3,NULL,&A);CHKERRQ(ierr);
ierr = FormJacobian_Grid(&fine_ctx,&A);CHKERRQ(ierr);
/* create linear solver */
ierr = KSPCreate(PETSC_COMM_WORLD,&ksp);CHKERRQ(ierr);
/* set values for rhs vector */
ierr = VecSet(fine_ctx.b,one);CHKERRQ(ierr);
/* set options, then solve system */
ierr = KSPSetFromOptions(ksp);CHKERRQ(ierr); /* calls PCSetFromOptions_ML if 'pc_type=ml' */
ierr = KSPSetOperators(ksp,A,A);CHKERRQ(ierr);
ierr = KSPSolve(ksp,fine_ctx.b,fine_ctx.x);CHKERRQ(ierr);
ierr = KSPGetIterationNumber(ksp,&its);CHKERRQ(ierr);
ierr = PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %D\n",its);CHKERRQ(ierr);
/* free data structures */
ierr = VecDestroy(&fine_ctx.x);CHKERRQ(ierr);
ierr = VecDestroy(&fine_ctx.b);CHKERRQ(ierr);
ierr = DMDestroy(&fine_ctx.da);CHKERRQ(ierr);
ierr = VecDestroy(&fine_ctx.localX);CHKERRQ(ierr);
ierr = VecDestroy(&fine_ctx.localF);CHKERRQ(ierr);
ierr = MatDestroy(&A);CHKERRQ(ierr);
ierr = KSPDestroy(&ksp);CHKERRQ(ierr);
ierr = PetscFinalize();
return ierr;
}
int main(int argc,char **argv)
{
PetscErrorCode ierr;
PetscInt its,n,Nx=PETSC_DECIDE,Ny=PETSC_DECIDE,nlocal,i;
PetscMPIInt size;
PC pc;
PetscInt mx,my;
Mat A;
GridCtx fine_ctx;
KSP ksp;
PetscBool flg;
PetscInitialize(&argc,&argv,NULL,help);
/* set up discretization matrix for fine grid */
/* ML requires input of fine-grid matrix. It determines nlevels. */
fine_ctx.mx = 9; fine_ctx.my = 9;
ierr = PetscOptionsGetInt(NULL,"-mx",&mx,&flg);CHKERRQ(ierr);
if (flg) fine_ctx.mx = mx;
ierr = PetscOptionsGetInt(NULL,"-my",&my,&flg);CHKERRQ(ierr);
if (flg) fine_ctx.my = my;
ierr = PetscPrintf(PETSC_COMM_WORLD,"Fine grid size %D by %D\n",fine_ctx.mx,fine_ctx.my);CHKERRQ(ierr);
n = fine_ctx.mx*fine_ctx.my;
MPI_Comm_size(PETSC_COMM_WORLD,&size);
ierr = PetscOptionsGetInt(NULL,"-Nx",&Nx,NULL);CHKERRQ(ierr);
ierr = PetscOptionsGetInt(NULL,"-Ny",&Ny,NULL);CHKERRQ(ierr);
ierr = DMDACreate2d(PETSC_COMM_WORLD, DMDA_BOUNDARY_NONE, DMDA_BOUNDARY_NONE,DMDA_STENCIL_STAR,fine_ctx.mx,
fine_ctx.my,Nx,Ny,1,1,NULL,NULL,&fine_ctx.da);CHKERRQ(ierr);
ierr = DMCreateGlobalVector(fine_ctx.da,&fine_ctx.x);CHKERRQ(ierr);
ierr = VecDuplicate(fine_ctx.x,&fine_ctx.b);CHKERRQ(ierr);
ierr = VecGetLocalSize(fine_ctx.x,&nlocal);CHKERRQ(ierr);
ierr = DMCreateLocalVector(fine_ctx.da,&fine_ctx.localX);CHKERRQ(ierr);
ierr = VecDuplicate(fine_ctx.localX,&fine_ctx.localF);CHKERRQ(ierr);
ierr = MatCreateAIJ(PETSC_COMM_WORLD,nlocal,nlocal,n,n,5,NULL,3,NULL,&A);CHKERRQ(ierr);
ierr = FormJacobian_Grid(&fine_ctx,&A);CHKERRQ(ierr);
/* create linear solver */
ierr = KSPCreate(PETSC_COMM_WORLD,&ksp);CHKERRQ(ierr);
ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr);
ierr = PCSetType(pc,PCML);CHKERRQ(ierr);
/* set options, then solve system */
ierr = KSPSetFromOptions(ksp);CHKERRQ(ierr); /* calls PCSetFromOptions_MG/ML */
for (i=0; i<3; i++) {
if (i<2) { /* test DIFFERENT_NONZERO_PATTERN */
/* set values for rhs vector */
ierr = VecSet(fine_ctx.b,i+1.0);CHKERRQ(ierr);
/* modify A */
ierr = MatShift(A,1.0);CHKERRQ(ierr);
ierr = MatScale(A,2.0);CHKERRQ(ierr);
ierr = KSPSetOperators(ksp,A,A,DIFFERENT_NONZERO_PATTERN);CHKERRQ(ierr);
} else { /* test SAME_NONZERO_PATTERN */
ierr = KSPSetOperators(ksp,A,A,SAME_NONZERO_PATTERN);CHKERRQ(ierr);
}
ierr = KSPSolve(ksp,fine_ctx.b,fine_ctx.x);CHKERRQ(ierr);
ierr = KSPGetIterationNumber(ksp,&its);CHKERRQ(ierr);
ierr = PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %D\n",its);CHKERRQ(ierr);
}
/* free data structures */
ierr = VecDestroy(&fine_ctx.x);CHKERRQ(ierr);
ierr = VecDestroy(&fine_ctx.b);CHKERRQ(ierr);
ierr = DMDestroy(&fine_ctx.da);CHKERRQ(ierr);
ierr = VecDestroy(&fine_ctx.localX);CHKERRQ(ierr);
ierr = VecDestroy(&fine_ctx.localF);CHKERRQ(ierr);
ierr = MatDestroy(&A);CHKERRQ(ierr);
ierr = KSPDestroy(&ksp);CHKERRQ(ierr);
ierr = PetscFinalize();
return 0;
}
