Strategies to vectorize conventional SCF-Cl algorithms

Recent high-performance computers, especially supercomputers, achieve very high-speed operations but bring about serious I/O problems in quantum chemical computations. Strategies to vectorize conventional SCF-CI algorithms are discussed relating to the I/O problems. The conventional SCF-CI algorithm which is proposed here reduces I/O processing by eliminating all sorting routines and redundant integral files and generates directly nonzero and nonredundant PK integrals with a vectorizable canonically-ordered list. The new implementation has been undertaken and successfully realized as a program system named GSCF3. The vector to scalar acceleration rate of GSCF3 on the HITAC S-810 are as follows: 2.5 5 in the AO integral evaluation, 5 12 in the SCF calculation, 15 30 in the four-index integral transformation, 10 20 in the CI matrix diagonalization, and overall 510 through SCF-CI.