[petsc-users] some problem with the VecCreateGhost.

[丁老师]

I want to know
1. What is the relationship between Vhat and LocalVhat. Is the LocalVhat a copy 
of the Vhat plus the Ghost values. I think the LocalVhat will consume more 
memeory than the Vhat, am i right?
2. can i direct call VecGetArrary to the Vhat if i do not operate on the ghost 
value.



    Vec Vhat;
    Vec LocalVhat;
    double* VhatVec;

  
VecCreateGhost(PETSC_COMM_WORLD,aMesh->Nx*aMesh->Ny/Commsize,PETSC_DECIDE,aMesh->nghosts,&aMesh->ghosts[0],&Vhat);
      
    VecGhostGetLocalForm(Vhat,&LocalVhat);
    VecGhostUpdateBegin(Vhat,INSERT_VALUES,SCATTER_FORWARD);
    VecGhostUpdateEnd(Vhat,INSERT_VALUES,SCATTER_FORWARD);