Yet another format is CSF (Compressed Sparse Fiber): http://glaros.dtc.umn.edu/gkhome/node/1177 http://glaros.dtc.umn.edu/gkhome/node/1177 It's a generalized C

Yet another format is CSF (Compressed Sparse Fiber): http://glaros.dtc.umn.edu/gkhome/node/1177 http://glaros.dtc.umn.edu/gkhome/node/1177 It's a generalized CSR/CSC (to ndim > 2) format that uses a tree data structure where each path from root to leaf encodes a nonzero element.