Optimization of the MPQS-factoring algorithm on the Cyber 205 and on the NEC SX-2

This paper describes the optimization of a program for the factorization of large integers on two large vector processors: a CDC Cyber 205 and a NEC SX-2. The factoring method used is the so-called multiple polynomial version of the quadratic sieve algorithm. Several large integers in the 48–92 decimal digits range have actually been factorized with these two programs. The largest number, the 92-digit composite (6−1)/(5 ·263 ·3931 ·6551), was factorized in about 95 CPUhours on the NEC SX-2. This result means a new absolute record for general purpose factoring methods. 1980 Mathematics Subject Classification (1985) revision: 11Y05, 11A51, 65F05, 65V05, 65W05.