Author: Robert Hyatt
Date: 06:58:34 02/10/06
Go up one level in this thread
On February 09, 2006 at 08:41:37, h.g.muller wrote: >On February 08, 2006 at 16:17:37, Robert Hyatt wrote: > >>Makes the code look ugly and awkward as hell, but it runs on "cachey" systems... > >I agree, it makes for ugly code. As a first step you have to 'stratify' all >natural loops into one that runs over a cache-size block and one that does the >courser steps, and then move all the former to the inside of nested loop >constructs. And be very aware when defining multi-dimensional array boundaries >to avoid unnecessary cache collisions, by inserting spacer elements. (But that >was important on the Cray too, although any stride was possible, memory bandwith >dropped like a stone if you took a power-of-two stride.) > >But it really pays off, on a PC it can easily make your code run 10 times >faster. For solving partial differential equations on multi-dimensional grids I >could achieve speeds of 60 MFLOPS even in the days of the 200MHz Pentium 1, >despite the fact that half the time was taken up by the 1% or so divisions among >the FLOPS. That was very competative, even with respect to collegues who had >their own private Cray that they could run 24/7. Because to beat those, I simply >bought 4 more PCs, something they could never hope to do with Crays. ;-) that's the reason there is no "cray crafty" in fact. :)
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.