Quang, You do start the persistent send requests as well right ? Assuming this is the case, that means you will start about 100K requests in one go. One of the problems might be the perception that the process is stuck, when in fact it simply progresses extremely slowly. Indeed, the MPI_Startall is a linear operation on the number of requests, and depending on the order in which you start them you might see behaviors you might not expect, but that are normal once you see understand the linear nature of the operation.
If you start first the 50K sends then you will end having 50k unexpected messages. If on the opposite you start first the receive, you will fail all the initial matching, and then when the send arrives you will potentially have to do again a linear search to identify the correct matching receive. Can you provide a replicator for this issue ? George. On Sat, Jul 1, 2017 at 4:22 PM, Quang Ha <quang.t.ha...@gmail.com> wrote: > Hi MPI-users, > > I am currently facing some troubles with persitance calling. The following > code describe the abstract I am trying to get out of: > > I am trying to implement some form of persistent calling. Somehow the > following code keeps hanging - I guessed I must have introduced a deadlock > but can't really wrap my head around it... > > MPI_Request r[2]; > MPI_Request s[2]; > int num_send = 1000; > [...] > MPI_Send_init(&Arr[1][1], num_send, MPI_DOUBLE, 1, A, MPI_COMM_WORLD, > &s[0]); > MPI_Recv_init(&Arr[1][0], num_send, MPI_DOUBLE, 0, A, MPI_COMM_WORLD, > &r[0]); > > MPI_Send_init(&Arr[2][1], num_send, MPI_DOUBLE, 0, B, MPI_COMM_WORLD, > &s[1]); > MPI_Recv_init(&Arr[2][0], num_send, MPI_DOUBLE, 1, B, MPI_COMM_WORLD, > &r[1]); > [...] > MPI_Startall(2, r); > MPI_Waitall(2, r, MPI_STATUSES_IGNORE); > > > This works kinda-fine if num_send is acceptably small. Once I reached > something like 10,000 or 50,000, the code just hang there without changing > anything. > > Is this phenomenon kinda expected? May I have some explanation for this > behaviour please? > > Many thanks, > Quang > > _______________________________________________ > users mailing list > users@lists.open-mpi.org > https://rfd.newmexicoconsortium.org/mailman/listinfo/users >
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