distributed array

[Berend van Wachem]

Dear Mat,


> One other thing,
> 
> in your function VecOverGlobalToBlockGlobalBegin and 
> VecOverGlobalToBlockGlobalEnd:
> 
> i assume that Vec *A is a the pointer to the blockglobal Vector?
> further Vec **B is an array of pointers to MPI vectors where each element of 
> the array is a MPI vector associated with one subblock?


A is the pointer to the single vector over the complete problem. This is 
the vector that will be used for the matrix computation. Indeed, *B is 
the pointer to an array of vectors which each correspond with a block.


> if that is so, then this is what i believe your functions are doing (please 
> correct me if i am wrong):
> 
> VecOverGlobalToBlockGlobalBegin: splits the blockglobal vector A into its MPI 
> subblock vectors
> 
> VecOverGlobalToBlockGlobalEnd: restores the vectors
> 
> And in between these two function calls you can mess with the MPI subblock 
> vectors?


Exactly.

> 
> then you iterate over all blocks (i assume this is the glueing part? )

I am not sure what you precisely mean. For glueing the blocks, I create 
an array of IS's which I scatter over. In my problem it's even more 
complicated than just that, because the I-direction in one block can be 
another direction in a neighbouring block which makes the 
neighbour-seeking a little more difficult. Once the IS are created, a 
scatter makes the neighbour values available to the current block. I use 
the same scatter once in the beginning to find out the addresses of the 
matrix locations.

Good luck,

Berend.