When creating an instance of uneven_block with the distribution [1, 0, 1] then the implementation incorrectly returns process id 1 (counting from 0) to be the owner of element id 1 (counting from zero), because the local starts of processes 1 and 2 are identical (local starts would be [0, 1, 1, 2] in this case).
In general, the implementation incorrectly assigns elements belonging to the first owner after one or more adjacent empty owners to the first of those empty ones.
I would suggest to change the implementation from
|
size_vector::const_iterator lb = std::lower_bound(local_starts.begin(), local_starts.end(), (std::size_t) i); |
|
return ((SizeType)(*lb) == i ? lb : --lb) - local_starts.begin(); |
to
size_vector::const_iterator ub = std::upper_bound(local_starts.begin(), local_starts.end(), (std::size_t) i);
return (--ub) - local_starts.begin();
Edit: Corrected mistake as pointed out below.
When creating an instance of uneven_block with the distribution [1, 0, 1] then the implementation incorrectly returns process id 1 (counting from 0) to be the owner of element id 1 (counting from zero), because the local starts of processes 1 and 2 are identical (local starts would be [0, 1, 1, 2] in this case).
In general, the implementation incorrectly assigns elements belonging to the first owner after one or more adjacent empty owners to the first of those empty ones.
I would suggest to change the implementation from
graph_parallel/include/boost/graph/parallel/distribution.hpp
Lines 225 to 226 in 22385cc
to
Edit: Corrected mistake as pointed out below.