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Re: [Scheme-reports] Bitwise operations on bytes

On Thu, 2012-03-29 at 12:11 -0700, Per Bothner wrote:
> I would expect the opposite: On modern systems arithmetic (including
> bitwise operations) is effectively free, but cache misses are
> expensive,
> so compact data structures are what counts.
> You wouldn't use a read-modify-write instruction except for "volatile"
> accesses. 

I can report at least one system (not Scheme) that I know promotes
bitvectors to bytevectors for speed purposes precisely because masking
out the bits is too expensive.  In my own tests this has been born out
as well.  

Aaron W. Hsu | arcfide@x | http://www.sacrideo.us
Programming is just another word for the lost art of thinking.

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