[gmx-developers] replica exchange

[Berk Hess]

servaas michielssens wrote:

> Dear,
>  
> I have a question about the repl_ex.c file in gromacs-3.3.2, in the 
> function replica_exchange( ) gmx_sum is called (line 10 in this 
> function). If I understood this correctly this function calculates the 
> sum of the potential energy on all nodes. I don't understand why this 
> function is called, why do you need the sum of the potential energies 
> of all the replica. Or is this just something to check that everything 
> is still ok on all the nodes?
>  

No, this is a lazy way of communicating the energies.
Each process fills one entry in an array of size #processes and then the 
array is summed
over the processes.
We already had this call and for this very infrequent event, I did not 
want to implement
another MPI routine to communicate energies.

Berk.