See https://github.com/nmslib/nmslib/issues/324#issuecomment-404524969
1.7.3.1
Resolving issue 327
1.7.2
1. Improving concurrency in Python (preventing hanging in a certain situation https://github.com/searchivarius/nmslib/issues/291) 2. Improving ParallelFor : passing thread ID and not starting threads in a single-thread mode.