No single ERI algorithm is available to efficiently handle all integral
classes; rather, each tends to have specific integral classes where the
specific algorithm outperforms the alternatives. The PRISM algorithm
389
Int. J. Quantum Chem.
(1991),
40,
pp. 753.
Link
is an intricate collection of pathways and steps in which the
path chosen is that which is the most efficient for a given class. It appears
that the most appropriate path for a given integral class depends on the
relative position of the contraction step (lowly contracted bra-kets prefer
late contraction, highly contracted bra-kets are most efficient with early
contraction steps).
Careful studies have provided FLOP counts which are the current basis of
integral algorithm selection, although care must be taken to ensure that
algorithms are not rate limited by MOPs.
352
Chem. Phys. Lett.
(1993),
206,
pp. 225.
Link
Future algorithm
selection criteria will take greater account of memory, disk, chip
architecture, cache size, vectorization and parallelization characteristics of
the hardware, many of which are already exist within Q-Chem.