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From: Christian Siebert (christian.siebert_at_[hidden])
Date: 2006-09-11 18:15:01


I stumbled across a serious bug in the tuned component of Open MPI,
which crashes for example the well-known HPL benchmark in conjunction
with the "native MPI_Bcast() patch" [1].

The problem is within the function ompi_coll_tuned_bcast_intra_chain(),
which does mainly the following:

  ompi_ddt_type_size( datatype, &typelng );
  segcount = segsize / typelng;
  num_segments = count / segcount;

Whenever you have a constructed type with a size larger than 'segsize'
(16384), you'll get a 'seqcount' of zero and finally a division by zero.

Happy fixing!