[petsc-users] Vecscatter question

[Barry Smith]

On Aug 29, 2011, at 8:32 PM, Tabrez Ali wrote:

> Hello
> 
> If during Vecscatter (say from a global vector x to a local vector y) if 'is' and 'iy' are such that almost all values being scattered happen to be on the local proc then almost 0 or very little MPI calls would be made internally. Is this correct?

  Yes, it does not use MPI to move the values locally. In fact, when possible it uses an efficient memcpy.

> 
> Such a setup would not cause scalability problems except consuming some local proc memory due to 'y', 'is' and 'iy' being larger than required.
> 
> Thanks in advance.
> 
> Tabrez
> 
>