[mpich-discuss] Error: "MPIR_Get_contextid_sparse_group(1193): Too many communicators (0/2048)"

Ted Sariyski tsariysk at craft-tech.com
Thu May 22 09:46:39 CDT 2014

It is about MPI_win. Here is the problem as it relates to MPI (it is a 
Boltzmann type equation).

There are N particles interacting with each other. Interaction is 
directional, so that a particle interacts only with those particles, 
which are within a narrow cone. The first step is to segregate the 
initial set of N particles into subsets of particles  (I called it 
'objects'),  which interact with each other. Here is what I do:

 1. Assign each object to a process.
 2. The process which owns a object:
      * Makes a guess for the maximum number of particles expected in
        this object.
      * Allocates memory for it.
      * Opens a shared window.
 3. All processes
      * Each particle identify which object it belongs to, and PUTs its
        data there.
 4. After assembly is done, objects are passed to a solver.
 5. Repeat

What do you mean with: "Why can’t all processes open one large window?" 
I guess I miss something.

On 05/21/2014 11:03 PM, Balaji, Pavan wrote:
> On May 21, 2014, at 6:02 PM, Ted Sariyski <tsariysk at craft-tech.com> wrote:
>> Memory limitations. With one large window all processes have to allocate memory for the objects they own as well as for objects assigned to other process.
> Are we talking about the same thing here?  I’m referring to an MPI_Win.  What objects do processes need to keep track of?
>    — Pavan
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