[RC5] Golomb Rulers (was "sexy" projects)

van der Stock, Andrew Andrew.vanderStock at nwhcn.org.au
Tue Mar 3 18:43:00 EST 1998


>Date: Mon, 02 Mar 98 22:29:46 -0500
>From: "Roy Wilson" <emperor at slic.com>
>Subject: Re: [RC5] Golomb Rulers (was "sexy" projects)
>
>On Mon, 02 Mar 1998 21:27:35 -0500, Charles P. Wright wrote:
>
>>This seems like a Bad Thing(tm) I have a decent system with 32 MB of ram
>>and X can take up to 20 or 30 (with lots of netscape windows) it seems
>>like a very bad idea to have a client that would cause so much swapping
>>and performance degradation.
>
>	The effort is based on AOL, what can you expect?  The clients are
>nice, but in comparison to the d.net setup, they're stone-age crude.

Why bag their ISP (or in this case both the ISP and the user)? AOL has
literally millions of users, and some of them have to be intelligent.

Many numerical computations take significant amounts of resources (otherwise
there wouldn't be a market for Crays or SGI's with terabytes of real RAM to
avoid swapping). Trading RAM and disk space for speed just seems a good deal
especially with the many Mkey/s freaks on this list. HD space is trivial
these days, but RAM is still an issue when you want to have a fully
transparent client. 

Maybe the algorithm can be made to search the file in a linear way (I
haven't checked if it already does this). If this is the case, the
choose.dat can be created by the client, and mmap()'d back into memory space
to be demand paged. In low memory situations, the working sets will be
small, which would alleviate memory woes on small memory machines (< 48 MB
of RAM, or less than 10 MB free to run the client). NT and most modern
Linux-like OS's have mmap() or equivalent calls. I'm not sure about Win95 (I
don't use it that often, and I rarely target it as a programming platform).

If choose.dat is constantly read randomly and written to on a regular basis,
it will not work as well, but it will still be better than having all the
RAM mapped at once. On most Linux-like OS's and NT, you can find out if
you're currently in over-committed mode, and maybe back off for a while (if
you put yourself to sleep for say 5 minutes, you'll be swapped out quite
quickly. When returning from sleep, check to see if it's safe to re-allocate
the RAM you freed before starting up again (ie the amount you need and maybe
another 20% on top for safety). 

Andrew
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