<div dir="ltr">Hi,<div><br></div><div>I am having some issues with the boost::mpi::communicator object.</div><div><br></div><div>I am trying to use the constructor call for the communicator object which is supposed to be equivalent to MPI_Comm_Create and I am experiencing deadlock. The plan is to build an vector of communicators, where if I have p^2 processors aligned in a p x p grid, I will build a communicator for every row and column, but, within a row/column with p processors, I will build p-2 more communicators, corresponding to successively removing the leftmost processor, for example if I have a 4 x 4 grid, I want to have:</div>

<div>0 1 2 3 &lt;-- one of these for every row/column</div><div>� �1 2 3 &lt;-- �</div><div>� � � 2 3 &lt;-- �these sub communicators, of course ignoring trivial ones.�</div><div><br></div><div>Originally i just had each processor building all of the groups it would belong to,</div>

<div>making sure that all processors build row communicators before column communicators, and that all processors in the same row/col built there communicators in the same order. This results in a strange deadlock. All processors enter the the correct constructor call, for example, processors 2,5,8 representing one column would attempt to build a sub communicator of the WORLD communicator, and they each have a group which lists 2,5,8, in the same sorted order, but they deadlock and never leave the call.</div>

<div><br></div><div>�When consulting the</div><div>manual page:�<a href="http://www.open-mpi.org/doc/v1.6/man3/MPI_Comm_create.3.php">http://www.open-mpi.org/doc/v1.6/man3/MPI_Comm_create.3.php</a></div><div>It is not clear if all processors in WORLD must execute this call or if only the ones within the group must execute it. When I try to have all processors execute such a call, I get a segmentation fault on the dtor call for the invalid communicator.</div>

<div><br></div><div>I&#39;m hoping someone can explain to me how to do this properly.</div><div><br clear="all"><div><div dir="ltr">Best,<br>-rhl<br></div></div>
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