We present an improved approximation algorithm for the covering 0-1 integer program (CIP), a well-known problem as a natural generalization of the set cover problem. Our algorithm uses a primal-dual algorithm for CIP by Fujito (2004) as a subroutine and achieves an approximation ratio of (f- (f-1)/m) when m is greater than or equal to 2, where m is the number of the constraints and f is the maximum number of non-zero entries in the constraints. In addition, when m=1 our algorithm can be regarded as a PTAS. These results improve the previously known approximation ratio f.
to appear in department of Industrial Engineering and Economics Working Paper, Tokyo Institute of Technology.