This directory contains a Hadoop implementation of sparse matrix multiply. Matrices are described in textual form as a list of nonzero entries, each of the form: row col value ID where row & col are the row & column indices (integers), value is the matrix entry, and ID is the name of the array. The main program, MatrixMultDriver, takes as arguments the file names of the two input matrices, the pathname for the output, and optionally the pathname for the directory in which to store intermediate files. The code was written for Hadoop version 0.13.0. It is not guaranteed to work with more recent versions of Hadoop. Files: MatrixMultDriver.java: Implements the main function BadGraphException.java: Graph.java: GraphEdge.java: Implement a graph suitable for representing sparse matrices P1Mapper.java: P1Reducer.java: P2Mapper.java: P2Reducer.java: Implement map and reduce operations for the two phases of matrix multiplication