The speedup curves were obtained on the Intel Paragon for an aryl
nitrenium ion (C4N2H6+) with a 6-31G** basis (C1 symmetry, 135 basis
functions, 25 occupied orbitals, all orbitals correlated). Superlinear
speedups are obtained relative to 2 processors because the number of
integral passes decreases when the number of processors increases (7
passes for nproc=2; 4 for nproc=4; 2 for nproc=8; and 1 for nproc>8).
For speedups measured relative to 16 processors, the ideal speedup curve
is linear as only one integral pass is required.