N-dimensional Sparse Matrices

N-dimensional sparse matrix and circular sparse matrix classes for arbitrary N. The classes support many common matrix operations including algebra, set operations, reduction, and more. All of these methods are efficiently implemented for sparse matrices. Very simple to use and very powerful!

Inspired by and improves on the Sandia National Labs sparse tensor toolbox http://csmr.ca.sandia.gov/~tgkolda/TensorToolbox/. See src_test for example use.