Hi Dougal,

Many (experts) have spoken before you on the optimization topic to include SSEx. The more optimized the less cross comparable results become from different computers, yes really when it gets down to folding and best energy calculations. Eventually a point will be reached that the lowest common denominator will no longer be supported and e.g. SSE2/3 becomes the new lowest minimum. Essentially though for each optimization, WCG has to add/debug 5/6/7 more science compiles per Operating System. At 3 commonly supported OSses that adds 15/18/21 applications to maintain and verify that the result is useful for the scientists.

Similarly follow discussion on optimization for 64 bit computers.

So picture, 32 bit + 64 bit versions for SSE and none SSE capable computers and you already got 4 versions for 1 science on 1 operating system. Why 64 bit also counts double though all have SSEx, is because a result in e.g. 32 bit without SSE gets pooled with 64 bit machines in e.g. HPF2 quorums. Every optimized compile requires a separate distribution and validation cycle, a monster support and management task at the scale WCG is running at.

They'll come, but then when is a big question mark.

cheers