The Zoltan project focuses on parallel algorithms for parallel combinatorial scientific computing, including partitioning, load balancing, task placement, graph coloring, matrix ordering, distributed data directories, and unstructured communication plans.

The Zoltan toolkit is an open-source library of MPI-based distributed memory algorithms.  It includes geometric and hypergraph partitioners, global graph coloring, distributed data directories using rendezvous algorithms, primitives to simplify data movement and unstructured communication, and interfaces to the ParMETIS, Scotch and PaToH partitioning libraries.  It is written in C and can be used as a stand-alone library.

The Zoltan2 toolkit is the next-generation toolkit for multicore architectures.  It includes MPI+OpenMP algorithms for geometric partitioning, architecture-aware task placement, and local matrix ordering.  It is written in templated C++ and is tightly integrated with the Trilinos toolkit.