Date: 2013-07-02T14:49:40+00:00

Actual source code: aspin.c
petsc-3.4.2 2013-07-02

      1: #include <petsc-private/snesimpl.h>             /*I   "petscsnes.h"   I*/
      2: #include <petscdm.h>

      6: PetscErrorCode MatMultASPIN(Mat m,Vec X,Vec Y)
      7: {
      9:   void           *ctx;
     10:   SNES           snes;
     11:   PetscInt       n,i;
     12:   VecScatter     *oscatter;
     13:   SNES           *subsnes;
     14:   PetscBool      match;
     15:   MPI_Comm       comm;
     16:   KSP            ksp;
     17:   PC             pc;
     18:   Vec            *x,*b;
     19:   Vec            W;
     20:   SNES           npc;

     23:   MatShellGetContext(m,&ctx);
     24:   snes = (SNES)ctx;
     25:   SNESGetPC(snes,&npc);
     26:   SNESGetFunction(npc,&W,NULL,NULL);
     27:   PetscObjectTypeCompare((PetscObject)npc,SNESNASM,&match);
     28:   if (!match) {
     29:     PetscObjectGetComm((PetscObject)snes,&comm);
     30:     SETERRQ(comm,PETSC_ERR_ARG_WRONGSTATE,"MatMultASPIN requires that the nonlinear preconditioner be Nonlinear additive Schwarz");
     31:   }
     32:   SNESNASMGetSubdomains(npc,&n,&subsnes,NULL,&oscatter,NULL);
     33:   SNESNASMGetSubdomainVecs(npc,&n,&x,&b,NULL,NULL);

     35:   VecSet(Y,0);
     36:   MatMult(npc->jacobian_pre,X,W);

     38:   for (i=0;i<n;i++) {
     39:     VecScatterBegin(oscatter[i],W,b[i],INSERT_VALUES,SCATTER_FORWARD);
     40:   }
     41:   for (i=0;i<n;i++) {
     42:     VecScatterEnd(oscatter[i],W,b[i],INSERT_VALUES,SCATTER_FORWARD);
     43:     VecSet(x[i],0.);
     44:     SNESGetKSP(subsnes[i],&ksp);
     45:     KSPGetPC(ksp,&pc);
     46:     PCApply(pc,b[i],x[i]);
     47:     VecScatterBegin(oscatter[i],x[i],Y,ADD_VALUES,SCATTER_REVERSE);
     48:   }
     49:   for (i=0;i<n;i++) {
     50:     VecScatterEnd(oscatter[i],x[i],Y,ADD_VALUES,SCATTER_REVERSE);
     51:   }
     52:   return(0);
     53: }

     57: /* -------------------------------------------------------------------------- */
     58: /*MC
     59:       SNESASPIN - Helper SNES type for Additive-Schwarz Preconditioned Inexact Newton

     61:    Options Database:
     62: +  -npc_snes_ - options prefix of the nonlinear subdomain solver (must be of type NASM)
     63: .  -npc_sub_snes_ - options prefix of the subdomain nonlinear solves
     64: .  -npc_sub_ksp_ - options prefix of the subdomain Krylov solver
     65: -  -npc_sub_pc_ - options prefix of the subdomain preconditioner

     67:     Notes: This routine sets up an instance of NETWONLS with nonlinear left preconditioning.  It differs from other
     68:     similar functionality in SNES as it creates a linear shell matrix that corresponds to the product:

     70:     \sum_{i=0}^{N_b}J_b({X^b_{converged}})^{-1}J(X + \sum_{i=0}^{N_b}(X^b_{converged} - X^b))

     72:     which is the ASPIN preconditioned matrix. Similar solvers may be constructed by having matrix-free differencing of
     73:     nonlinear solves per linear iteration, but this is far more efficient when subdomain sparse-direct preconditioner
     74:     factorizations are reused on each application of J_b^{-1}.

     76:    Level: intermediate

     78: .seealso:  SNESCreate(), SNES, SNESSetType(), SNESNEWTONLS, SNESNASM, SNESGetPC(), SNESGetPCSide()

     80: M*/
     81: PETSC_EXTERN PetscErrorCode SNESCreate_ASPIN(SNES snes)
     82: {
     84:   SNES           npc;
     85:   KSP            ksp;
     86:   PC             pc;
     87:   Mat            aspinmat;
     88:   MPI_Comm       comm;
     89:   Vec            F;
     90:   PetscInt       n;
     91:   SNESLineSearch linesearch;

     94:   /* set up the solver */
     95:   SNESSetType(snes,SNESNEWTONLS);
     96:   SNESSetPCSide(snes,PC_LEFT);
     97:   SNESGetPC(snes,&npc);
     98:   SNESSetType(npc,SNESNASM);
     99:   SNESNASMSetComputeFinalJacobian(npc,PETSC_TRUE);
    100:   SNESGetKSP(snes,&ksp);
    101:   KSPGetPC(ksp,&pc);
    102:   PCSetType(pc,PCNONE);
    103:   PetscObjectGetComm((PetscObject)snes,&comm);
    104:   SNESGetLineSearch(snes,&linesearch);
    105:   SNESLineSearchSetType(linesearch,SNESLINESEARCHBT);

    107:   /* set up the shell matrix */
    108:   SNESGetFunction(snes,&F,NULL,NULL);
    109:   VecGetLocalSize(F,&n);
    110:   MatCreateShell(comm,n,n,PETSC_DECIDE,PETSC_DECIDE,snes,&aspinmat);
    111:   MatSetType(aspinmat,MATSHELL);
    112:   MatShellSetOperation(aspinmat,MATOP_MULT,(void(*)(void))MatMultASPIN);

    114:   SNESSetJacobian(snes,aspinmat,NULL,NULL,NULL);
    115:   MatDestroy(&aspinmat);

    117:   return(0);
    118: }