Effective data distribution and parallelization of computations involving irregular data structures is a challenging task. We address the twin-problems in the context of computations involving block-sparse matrices. The programming model provides a global view of a distributed block-sparse matrix. Abstractions are provided for the user to express the parallel tasks in the computation. The tasks are mapped onto processors to ensure load balance and locality. The abstractions are based on the Aggregate Remote Memory Copy Interface, and are interoperable with the Global Arrays programming suite and MPI. Results are presented that demonstrate the utility of the approach.