henry@utzoo.uucp (Henry Spencer) (10/25/89)
In article <2492@munnari.oz.au> ok@cs.mu.oz.au (Richard O'Keefe) writes: >... Let's just stop and calculate for a second. How big a >square matrix of IEEE doubles will fit into 2M? N**2 * 8 = 2 * 1024**2 >means N = 512. (The "2M of programs running at once" has to include the >data they are currently working with!) Ok, linear programming on a >personal computer is out... It's out regardless, actually. "Stop and calculate for a second" becomes "stop and calculate for several days" if you try to operate on arrays that won't fit into memory. Virtual memory does not remove memory limits, it just makes them soft (performance slowly goes to zero) rather than hard (program won't run if it's one byte over the limit). Virtual memory is not magic; there is no substitute for *real* memory if you want performance. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
ok@cs.mu.oz.au (Richard O'Keefe) (10/26/89)
In article <1989Oct24.175530.2663@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes: > In article <2492@munnari.oz.au> ok@cs.mu.oz.au (Richard O'Keefe) writes: > >... Let's just stop and calculate for a second. How big a > >square matrix of IEEE doubles will fit into 2M? > Virtual memory is not > magic; there is no substitute for *real* memory if you want performance. I'm afraid that Henry Spencer missed my point. My reference to wanting to do linear programming on a personal computer was not an argument for virtual memory, but a riposte to a claim that "2M on a personal computer is enough". That more than 2M of real memory may be needed is precisely my point. How much real memory is "enough" for a personal computer? As much as will justify its price.
n62@nikhefh.nikhef.nl (Klamer Schutte) (10/27/89)
In article <2535@munnari.oz.au> ok@cs.mu.oz.au (Richard O'Keefe) writes: >My reference to wanting to do linear programming on a personal computer >was not an argument for virtual memory, but a riposte to a claim that > "2M on a personal computer is enough". >That more than 2M of real memory may be needed is precisely my point. >How much real memory is "enough" for a personal computer? As much as >will justify its price. But, when 2M is not enough, but only the amount equivalent to the money you can (and be willing) to spend, than virtual memory is an item: This will allow you to run the program of somebody else (who is writing all his code himself) who had more money to spend! Yes, i want virtual memory to minix. Yes, i realise it is (virtually) impossible on my ST. Yes, i know it will be unacceptable slow on a stock PC. But people keep dreaming... Klamer. -- _____________________Yes, mail address changed again :-(________________________ Klamer Schutte mcvax!nikhefh!{n62,Schutte} {Schutte,n62}@nikhef.nl