Identity Testing for constant-width, and commutative, read-once oblivious ABPs

We give improved hitting-sets for two special cases of Read-once Oblivious Arithmetic Branching Programs (ROABP). First is the case of an ROABP with known variable order. The best hitting-set known for this case had cost (nw)O(log n) where n is the number of variables and w is the width of the ROABP. Even for a constant-width ROABP, nothing better than a quasi-polynomial bound was known. We improve the hitting-set complexity for the known-order case to nO(log w) . In particular, this gives the first polynomial time hitting-set for constant-width ROABP (known-order). However, our hitting-set works only over those fields whose characteristic is zero or large enough. To construct the hitting-set, we use the concept of the rank of partial derivative matrix. Unlike previous approaches whose basic building block is a monomial map, we use a polynomial map. The second case we consider is that of commutative ROABP. The best known hitting-set for this case had cost dO(log w) (nw)O(log log w) ...

• Type: Journal
• Year: 2016
• Where: ECCC
• Authors: Rohit Gurjar, Arpita Korwar, Nitin Saxena
• Keywords: ECCC 2016