int main(int argc,char **argv)
{
PetscErrorCode ierr;
Vec v,s; /* vectors */
PetscInt n = 20;
PetscScalar one = 1.0;
PetscInitialize(&argc,&argv,(char*)0,help);
ierr = PetscOptionsGetInt(PETSC_NULL,"-n",&n,PETSC_NULL);CHKERRQ(ierr);
/*
Create multi-component vector with 2 components
*/
ierr = VecCreate(PETSC_COMM_WORLD,&v);CHKERRQ(ierr);
ierr = VecSetSizes(v,PETSC_DECIDE,n);CHKERRQ(ierr);
ierr = VecSetBlockSize(v,2);CHKERRQ(ierr);
ierr = VecSetFromOptions(v);CHKERRQ(ierr);
/*
Create single-component vector
*/
ierr = VecCreate(PETSC_COMM_WORLD,&s);CHKERRQ(ierr);
ierr = VecSetSizes(s,PETSC_DECIDE,n/2);CHKERRQ(ierr);
ierr = VecSetFromOptions(s);CHKERRQ(ierr);
/*
Set the vectors to entries to a constant value.
*/
ierr = VecSet(v,one);CHKERRQ(ierr);
/*
Get the first component from the multi-component vector to the single vector
*/
ierr = VecStrideGather(v,0,s,INSERT_VALUES);CHKERRQ(ierr);
ierr = VecView(s,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
/*
Put the values back into the second component
*/
ierr = VecStrideScatter(s,1,v,ADD_VALUES);CHKERRQ(ierr);
ierr = VecView(v,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
/*
Free work space. All PETSc objects should be destroyed when they
are no longer needed.
*/
ierr = VecDestroy(&v);CHKERRQ(ierr);
ierr = VecDestroy(&s);CHKERRQ(ierr);
ierr = PetscFinalize();
return 0;
}
/*
Here is my custom preconditioner
Capital vectors: X, X1 are global vectors
Small vectors: x, x1 are local ghosted vectors
Prefixed a: ax1, aY1 are arrays that access the vector values (either local (ax1) or global aY1)
*/
PetscErrorCode MyPCApply(PC pc,Vec X,Vec Y)
{
AppCtx *app;
PetscErrorCode ierr;
Vec X1,X2,X3,x1,x2,Y1,Y2,Y3;
DALocalInfo info1,info2,info3;
DA da1,da2,da3;
PetscInt i,j;
FluidField *ax1,*aY1;
PetscScalar **ax2,**aY2;
PetscFunctionBegin;
ierr = PCShellGetContext(pc,(void**)&app);
CHKERRQ(ierr);
/* obtain information about the three meshes */
ierr = DMCompositeGetEntries(app->pack,&da1,&da2,&da3);
CHKERRQ(ierr);
ierr = DAGetLocalInfo(da1,&info1);
CHKERRQ(ierr);
ierr = DAGetLocalInfo(da2,&info2);
CHKERRQ(ierr);
ierr = DAGetLocalInfo(da3,&info3);
CHKERRQ(ierr);
/* get ghosted version of fluid and thermal conduction, global for phi and C */
ierr = DMCompositeGetAccess(app->pack,X,&X1,&X2,&X3);
CHKERRQ(ierr);
ierr = DMCompositeGetLocalVectors(app->pack,&x1,&x2,PETSC_NULL);
CHKERRQ(ierr);
ierr = DAGlobalToLocalBegin(da1,X1,INSERT_VALUES,x1);
CHKERRQ(ierr);
ierr = DAGlobalToLocalEnd(da1,X1,INSERT_VALUES,x1);
CHKERRQ(ierr);
ierr = DAGlobalToLocalBegin(da2,X2,INSERT_VALUES,x2);
CHKERRQ(ierr);
ierr = DAGlobalToLocalEnd(da2,X2,INSERT_VALUES,x2);
CHKERRQ(ierr);
/* get global version of result vector */
ierr = DMCompositeGetAccess(app->pack,Y,&Y1,&Y2,&Y3);
CHKERRQ(ierr);
/* pull out the phi and C values */
ierr = VecStrideGather(X3,0,app->dx,INSERT_VALUES);
CHKERRQ(ierr);
ierr = VecStrideGather(X3,1,app->c,INSERT_VALUES);
CHKERRQ(ierr);
/* update C via formula 38; put back into return vector */
ierr = VecAXPY(app->c,0.0,app->dx);
CHKERRQ(ierr);
ierr = VecScale(app->c,1.0);
CHKERRQ(ierr);
ierr = VecStrideScatter(app->c,1,Y3,INSERT_VALUES);
CHKERRQ(ierr);
/* form the right hand side of the phi equation; solve system; put back into return vector */
ierr = VecAXPBY(app->dx,0.0,1.0,app->c);
CHKERRQ(ierr);
ierr = DMMGSolve(app->fdmmg);
CHKERRQ(ierr);
ierr = VecStrideScatter(app->dy,0,Y3,INSERT_VALUES);
CHKERRQ(ierr);
/* access the ghosted x1 and x2 as arrays */
ierr = DAVecGetArray(da1,x1,&ax1);
CHKERRQ(ierr);
ierr = DAVecGetArray(da2,x2,&ax2);
CHKERRQ(ierr);
/* access global y1 and y2 as arrays */
ierr = DAVecGetArray(da1,Y1,&aY1);
CHKERRQ(ierr);
ierr = DAVecGetArray(da2,Y2,&aY2);
CHKERRQ(ierr);
for (i=info1.xs; i<info1.xs+info1.xm; i++) {
aY1[i].prss = ax1[i].prss;
aY1[i].ergg = ax1[i].ergg;
aY1[i].ergf = ax1[i].ergf;
aY1[i].alfg = ax1[i].alfg;
aY1[i].velg = ax1[i].velg;
aY1[i].velf = ax1[i].velf;
}
for (j=info2.ys; j<info2.ys+info2.ym; j++) {
for (i=info2.xs; i<info2.xs+info2.xm; i++) {
aY2[j][i] = ax2[j][i];
}
}
ierr = DAVecRestoreArray(da1,x1,&ax1);
CHKERRQ(ierr);
ierr = DAVecRestoreArray(da2,x2,&ax2);
CHKERRQ(ierr);
ierr = DAVecRestoreArray(da1,Y1,&aY1);
CHKERRQ(ierr);
ierr = DAVecRestoreArray(da2,Y2,&aY2);
CHKERRQ(ierr);
ierr = DMCompositeRestoreLocalVectors(app->pack,&x1,&x2,PETSC_NULL);
CHKERRQ(ierr);
ierr = DMCompositeRestoreAccess(app->pack,X,&X1,&X2,&X3);
CHKERRQ(ierr);
ierr = DMCompositeRestoreAccess(app->pack,Y,&Y1,&Y2,&Y3);
CHKERRQ(ierr);
PetscFunctionReturn(0);
}
