15 Nov
2005
15 Nov
'05
9:49 a.m.
On Tue, Nov 15, 2005 at 02:12:55PM +0100, Jens M Andreasen wrote:
(good to see you're back on line :-)
On a related subject: How is level one cache replaced
with new data,
should one (or ones compiler) decide to use some of the prefetch
instructions available from Intel PII and up? It would make sense to
fetch the next dataset while doing what has to be done "now". On the
other hand, overwriting the current dataset is somewhat counter
productive.
Unless you're hand-coding assembly it's probably wisest to leave this
to the compiler. OTOH, I've no idea how smart gcc/g++ is in this respect.
It could be quite interesting to -S some familiar DSP code and have a
look at the result.
The only place where I've seen prefetch used explicitly is in Brutefir's
sse and 3dnow routines which I recently modified for use in one of my own
projects.
The layout of the data would influence these
decisions, no?
And conversely, considerations relating to cache use (and possible sse
optimisations) may influence your choice of data formats.
--
FA