Path: utzoo!attcan!uunet!decwrl!sdd.hp.com!zaphod.mps.ohio-state.edu!sunybcs!uhura.cc.rochester.edu!leadley From: leadley@uhura.cc.rochester.edu (Scott Leadley) Newsgroups: comp.arch Subject: Re: LINPACK 1000x1000 MFLOPS per $$$ Message-ID: <8576@ur-cc.UUCP> Date: 25 Jul 90 15:51:20 GMT References: <2349@crdos1.crd.ge.COM> <37683@ucbvax.BERKELEY.EDU> Reply-To: leadley@uhura.cc.rochester.edu (Scott Leadley) Organization: University of Rochester Lines: 55 In article mccalpin@perelandra.cms.udel.edu (John D. McCalpin) writes: ... >In article <37683@ucbvax.BERKELEY.EDU> elm@sprite.Berkeley.EDU (ethan miller) asks: ... >> Really? That's 5000 hours on a PowerStation (using the 25/1 ratio from >> the table). That's about 200 days, assuming you use every single CPU >> cycle on the machine. Since you'll be doing some I/O, though, I'd be >> surprised to see better than 50-75% utilization, which brings total >> running time to close to a year. Granted, it's cheaper than Cray time, >> but is it practical to wait a year for a single simulation to finish? > >200 days is a good starting estimate. I actually get more like 95% >cpu utilization on this job, so figure 7 months calendar time. The >interesting aspect is that the whole process of proposal review and >funding takes about 6 months from the time the proposal is submitted >to the time that the money is available. If you include the time spent >actually writing the proposal, then 7 months on the calendar is not at >all unreasonable an estimate. ... >In light of this, waiting 7 months for a dedicated server to finish is >not so silly as it first sounded. What is the mean time between crashes on your PowerStation? What is the mean time between power glitches? (Maybe a UPS would be a good investment.) I agree that having a personal PowerStation is the most cost effective per MFLOP for your purposes. However, I don't think that is the only measure of worth in this debate. Here are some other measures of worth: - is the simulation amenable to checkpointing? This is important if you have to worry about the mean time between failure of the system as a whole. - how much effort does it take on the part of the researcher to restart from a checkpoint? This can be a significant time sink with some programs. - does the work require substantial support by a human? Mounting and unmounting tapes, for example. - is the system hardware and software reliable when used for your purposes? All systems require some administrative effort. However, having just one user and a well-behaved task can reduce this effort to close to nothing. - does use of the system require interacting with other people? Having to coordinate your work with other people is sometimes a a hassle (depending on the people or the situation). Having to conform to the procedures of a bureaucracy is always a hassle. - how easy is it to recover from a system failure? If the researcher is not familar with the system and doesn't have access to the services of a knowledgeable systems support person, system failures (due to crashes, file corruption, inept system administration, etc.) can be catastrophic. I'm playing devil's advocate here, in a similar situation I'd make the same choice you did (and probably quicker too since I am a fan of decentralized computing). -- Scott Leadley - leadley@cc.rochester.edu