I was wondering about a problem in analyzing a social network (counting friends-in-common between all pairs of members) that requires squaring its adjacency matrix, and started reading up on algorithms for multiplying sparse matrices.
However, all I found so far were different ways of arranging the more or less naive "outer product" algorithm between processors - the same total number of multiplications/additions with different amounts of communication and additional algorithmic overhead (which, though, is undoubtedly important).
The most non-trivial algorithm I found was the Yuster-Zwick algorithm described in Fast sparse matrix multiplication, which is basically a combination of the same old naive algorithm and using a fast dense method for the dense part of the problem.
I looked at how sparse matrix multiplication is implemented in MLLib and it, too, appears to use the simple block-based algorithm.
Are there any parallel algorithms for multiplying sparse matrices that are substantially different from the naive one - as different as Strassen's or Coppersmith-Winograd's algorithms are from the naive algorithm for multiplying dense matrices?
For concreteness, let us assume that the matrices are sparse enough that number of non-zeros in the arguments and in the result are both $O(N)$.
