[Trilinos-Users] Question concerning the Epetra BlockMap function : RemoteIDList

[John Jomo]

Hi Mike,

I wrote a small test which shows that the function stalls when the 
function  RemoteIDList()
is not called in a collective operation. The test is attached to this mail.

I managed to find a work around in my algorithm. For my application, I 
first sort out the indices to be queried and make one call to the function
RemoteIDList(). But I would be still interested to know if a 
non-collective call can be made to RemoteIDList().

Short description of the test:
16 indices are divided among 4 processes and a connectivity map which 
defines how the different indices are connected to each other is stored on
every process. This mimics the sparsity pattern of a finite element 
mesh. I chose a non-symmetric map for the test and query the location of 
a set of indices on every process.

thanks for all the help. At least now I can continue developing my code :)

John.


On 18.09.2015 00:52, Heroux, Michael A wrote:
> I believe the collective operation is only performed on the first call for
> any given map.  If this is the case, you should be able to do a pre-call
> of the RemoteIDList() method, making sure that all processes are
> participating.  Then subsequent calls would be safe.
>
> It is worth a try.  If that does not work, please send some output, or if
> making a small test case is possible, please do that.
>
> Thanks.
>
> Mike
>
> On 9/17/15, 3:54 PM, "Trilinos-Users on behalf of John Jomo"
> <trilinos-users-bounces at trilinos.org on behalf of john.jomo at tum.de> wrote:
>
>> Hallo Mike,
>>
>> looked at my algorithm again and found out that not all processes are
>> participating in the call thus the stall.
>> Is there a way to make this call on a subset of processes?
>>
>> Thanks for the help.
>>
>> John.
>>
>> On 17.09.2015 19:32, Heroux, Mike wrote:
>>> John,
>>>
>>> A few thoughts:
>>>
>>> - Generally speaking, this is a collective call, so all MPI processes
>>> need
>>> to participate in the call.  Some logic paths through the function don¹t
>>> require communication if the situation is simple enough to compute with
>>> local data.
>>> - Check error codes to see if there is a non-zero value being returned.
>>>
>>> Mike
>>>
>>> On 9/17/15, 11:09 AM, "Trilinos-Users on behalf of John Jomo"
>>> <trilinos-users-bounces at trilinos.org on behalf of john.jomo at tum.de>
>>> wrote:
>>>
>>>> Hallo everyone,
>>>>
>>>> here is a question concerning Epetra:
>>>>
>>>> I have created a distributed Epetra_BlockMap and I'm trying to find out
>>>> on which processes a set of Ids reside using the RemoteIDList command.
>>>>
>>>> I run a loop over the function  making repeated queries using different
>>>> values of "IdsToQuery"
>>>> int error = myMap->RemoteIDList( numberOfIds, &( IdsToQuery[0] ), &(
>>>> processorIds[0] ), &( localIds[0] ));
>>>>
>>>> For some strange reason some processes find all Ids while others stall
>>>> within the function causing a deadlock  :(
>>>>
>>>> I thought the problem was caused by mutlithreading so I pinned the
>>>> mpi-processes to the cores and made sure that I only used one process
>>>> per core. This however did not solve the problem.
>>>>
>>>> Would really appreciate some help on this.
>>>>
>>>> thanks in advance
>>>>
>>>>
>>>> John.
>>>>
>>>>
>>>>
>>>> -- 
>>>> John Jomo M.Sc.
>>>> Technische Universität München
>>>> Computation in Engineering
>>>> Simulation in Applied Mechanics - SAM
>>>> Arcisstraße 21
>>>> 80333 München
>>>> Tel.:     0049 / 89 / 289 25064
>>>> Fax:      0049 / 89 / 289 25051
>>>> E-Mail:john.jomo at tum.de<mailto:john.jomo at tum.de>
>>>> Internet:www.cie.bgu.tum.de<http://www.cie.bgu.tum.de/>
>>>>
>>>> _______________________________________________
>>>> Trilinos-Users mailing list
>>>> Trilinos-Users at trilinos.org
>>>> https://trilinos.org/mailman/listinfo/trilinos-users
>> -- 
>> John Jomo M.Sc.
>> Technische Universität München
>> Computation in Engineering
>> Simulation in Applied Mechanics - SAM
>> Arcisstraße 21
>> 80333 München
>> Tel.:     0049 / 89 / 289 25064
>> Fax:      0049 / 89 / 289 25051
>> E-Mail:   john.jomo at tum.de<mailto:john.jomo at tum.de>
>> Internet: www.cie.bgu.tum.de<http://www.cie.bgu.tum.de/>
>>
>> _______________________________________________
>> Trilinos-Users mailing list
>> Trilinos-Users at trilinos.org
>> https://trilinos.org/mailman/listinfo/trilinos-users

-- 
John Jomo M.Sc.
Technische Universität München
Computation in Engineering
Simulation in Applied Mechanics - SAM
Arcisstraße 21
80333 München
Tel.:     0049 / 89 / 289 25064
Fax:      0049 / 89 / 289 25051
E-Mail:   john.jomo at tum.de<mailto:john.jomo at tum.de>
Internet: www.cie.bgu.tum.de<http://www.cie.bgu.tum.de/>

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