3 new mac VMs + pending Mac VM...

John M McIntosh johnmci at smalltalkconsulting.com
Wed Oct 11 01:40:30 UTC 2000


>Hi guys,
>
>I too was wondering if the Squeak VM was taking advantage of the 
>architecture in such things as the G4 processor...  It is 1/3 
>General purpose registers, 1/3 Floating Point registers and 1/3 
>Vector registers...  The vectors can do 4, 8 or 16 way paralleism... 
>That is 4 time faster, 8 times faster and 16 times faster guys...
>
>Squeak seems to be goofing around in areas I think could go much 
>faster with the use of the additional architecture in the G4... 
>Signal and image processing tasks like FFTs and Compression, crypto, 
>3D and more...  And what of the workings of the VM itself?  Did I 
>see a Vector plugin somewhere?
>
>Mabe Dan or Ian could jump in here...
>
>-Rick-
>


Well take for example vector math v[] <- x[] + y[]  where x and y are 
two float arrays. I looked at this last winter and found that the 
setup time for Squeak to process the +, which it first attempts as an 
integer to integer, then float/float, then falls back to a send which 
then calls the primitive in the plugin to do the math this takes 999 
milliseconds, the other 1 millisecond is taken to do the math for say 
10,000 elements. Now these numbers aren't correct, but you get the 
idea, so if I save 50% off the time to do the math then instead of 
1000 milliseconds it takes 999.5... Soooo you must find other areas, 
like graphics were you mix millions of bits to save some real time.



PS Somewhere on my list is to think about changing the math 
primitives to fallback to vector processing if integer then float 
doesn't work... However time constraints have prevented it. Besides 
the usage of vector math isn't high in Squeak, Alice for example does 
do as much vector math as one would first think... Say a couple of 
100 thousand iterations over a billion or two CPU cycles...


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John M. McIntosh <johnmci at smalltalkconsulting.com> 1-800-477-2659
Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
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Custom Macintosh programming & various Smalltalk dialects
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