CCL: W:hardware for computational chemistry calculations

["Perry E. Metzger" <perry^^^piermont.com>]

 Sent to CCL by: "Perry E. Metzger" [perry(~)piermont.com]
 "Perry E. Metzger perry===piermont.com"
 <owner-chemistry^_^ccl.net> writes:
 > Lets say you have a computation that is I/O bound on access to a 10G
 > file. Right now, an additional 10G of DRAM will cost ~$1200.
 Er, I'm not being quite 100% careful there. The price can end up being
 twice that or more depending on speed and configuration, and only rare
 AMD64 server motherboards will allow you to put enough in. The
 principle, though, is important (and of course, every year the prices
 will be half what they were and the densities twice what they were, so
 the principle will continue to apply). The way you should figure this
 out is: if I can keep my entire working set of files in RAM (something
 the buffer cache mechanisms can easily do on Linux or NetBSD or
 FreeBSD), will it speed things up so much that I don't need to buy
 enough more machines that the price tradeoff for a "crazy amount of
 memory" is actually not crazy at all. With time, for most problems,
 the needle points more and more often towards "get more RAM" than
 "get
 a faster disk". The obvious exception is stuff where getting things
 onto disk is mandatory (database servers), and where your working set
 is so large (right now past, say, 16G, soon much larger) that it is
 literally not going to be practical to get a machine with that much
 memory. Below that size, you owe it to yourself to do the calculation...
 Perry