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

[Rajeev Thakur]

I don't fully understand your use case, but:

The window memory passed to MPI_Win_create on each process must be a contiguous memory. You can internally manage it in whatever way.

If you create a datatype on a process, the datatype is local to that process. Other processes can't use that datatype.

Also the MPI standard says the following about the target datatype passed to put/get/accumulate (MPI-3, pg 420, line 33):
"The target datatype must contain only relative displacements, not absolute addresses."

Rajeev


On May 23, 2014, at 9:44 AM, Ted Sariyski <tsariysk at craft-tech.com> wrote:

> I need a little bit more help. My question relates to the structure of the array (referred below as A), for which a window object will be created.  
> 
> Let say that particles are of type particle_t:
> 
> type particle_t
>       integer :: host, id,...
>       real,pointer :: data(:)=>null()
> end type particle_t
> 
> I built two corresponding mpi types, one with data allocated, mpi_particles_t, and mpi_particles_null_t, when p%data=>null().
> 
> What I want to do is the following:
> 	•  All processes allocates an array of type particles_t for all particles, but data is allocated only if a particle is assigned to  the domain:
>             allocate(A(tot_num_particles))
>                do n=1,tot_num_particles
>                    if ( particle(n)%host == myid)    allocate(particle(n)%data(data_size))
>                 enddo
> 
>     2. All processes create their mpi data type mpi_A_t:
> 
>       do n=1,tot_num_particles
> 
>             if ( particle(n)%host == myid)  then   
>                   blockcounts(n) = 1 ; oldtypes(n) = mpi_particles_t
>               else   
>                   blockcounts(n) = 1 ; oldtypes(n) = mpi_particles_null_t
>            endif
>             call MPI_GET_ADDRESS(A(n), offsets(n), ierr)
>         enddo
> 
>        call mpi_type_create_struct(tot_num_particles,blockcounts,offsets,oldtypes,mpi_A_myid_t,ierr)
>         call mpi_type_commit(mpi_A_myid_t,ierr)
>         
> I gave a try but it fails. Before I proceed I want to make sure that there is nothing fundamentally wrong with this approach. Besides, even if it is correct, I am not sure that this is the 'best' solution. I will highly appreciate your comments.
> 
> Thanks in advance,
> --Ted
> 
> 
> 
> 
> 
> On 05/22/2014 03:31 PM, Ted Sariyski wrote:
>> I see.  Thanks a lot. 
>> --Ted 
>> 
>> 
>> On 05/22/2014 03:15 PM, Rajeev Thakur wrote: 
>>>> What do you mean with: "Why can’t all processes open one large window?" I guess I miss something. 
>>> If each process has an array of objects that belong to it (called array A say) , then with a single call to MPI_Win_create you can create a window object that has everyone's A arrays in it. 
>>> 
>>> Rajeev 
>>> 
>>> 
>>> 
>>> On May 22, 2014, at 9:46 AM, Ted Sariyski <tsariysk at craft-tech.com> wrote: 
>>> 
>>>> 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: 
>>>>     • Assign each object to a process. 
>>>>     • 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. 
>>>>     • All processes 
>>>>         • Each particle identify which object it belongs to, and PUTs its data there. 
>>>>     • After assembly is done, objects are passed to a solver. 
>>>>     • Repeat 
>>>> What do you mean with: "Why can’t all processes open one large window?" I guess I miss something. 
>>>> Thanks, 
>>>> --Ted 
>>>> 
>>>> 
>>>> 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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