ate for calculations on large molecules in small basis sets,
or when using machines with very high latencies. The <I>revised
algorithm</I> groups atoms into blocks, looping over quartets of
blocks of atoms, and then evaluating all integrals within a quartet of
blocks of atoms.  Sparsity may still be exploited in the outer loops
and the performance gains include

<UL>
<LI> many fewer, larger messages,
<LI> elimination of sensitivity to message-passing latency,
<LI> reduction of communication costs to less th