Posted by  Chris Dillman on February 10, 2004 at 13:44:08:

>On Tuesday, February 10, 2004, at 07:11 pm, Chris Dillman wrote:
>
>>Would a look up table be faster in some cases or a less accurate sqrt call?
>>Or is the more accurate called really needed in Quesa?
>>
>
>With the current architecture of the Mac at least, using a look up
>table is actually
>slower as the processor has to load four words from main RAM into
>the processor
>cache, and each of the four accesses take so long compared with the speed of
>the processor that is actually quicker to work out the value. I know
>this sounds
>weird as it took a lot of testing before I relegated one of my
>favourite algorithms

Ok cool.

This means I need to check the speed of my look up tables in my own
game engine...

Which has a lot in common with Quesa on the inside.

>- the large look up table - to the pages of history. For small
>tables, after a few
>uses the entire table gets into the cache, but large tables are now a no no.
>Somehow turning off the cache before accessing RAM might help but that is
>something which sounds dangerous, maybe even more so in dual processor Macs.

Now what would you consider a large table?
I mean in size etc?

>Roger Holmes.

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