1. Re: Encrypting (and bit-shifting)
- Posted by Pete Eberlein <xseal at HARBORSIDE.COM>
Jul 09, 1997
-
Last edited Jul 10, 1997
Robert Craig wrote:
> > 2. Bit shifting for Euphoria. Much needed Speed increase
>
> The speed ratio between shifting versus multiplying or dividing
> by a power of two, would not be as great in Euphoria as it
> is in C or assembly language. Each operation in Euphoria
> has a bit of overhead attached to it. Nevertheless it's probably
> worth adding shifts. (integer divide by the constant "2" is already done
> as a shift right).
What about dividing by constant powers of 2? Is this done using a
number of shift right's?
I have been using fixed point arithmetic in some graphics routines I
have been working on. The whole number portion of the value is stored
in the upper two bytes of a Euphoria integer and the fractional part in
the lower two bytes. To access the whole number only, I have to divide
the value by 2^16 (65536). My code just screams at me "shift
optimization!" If I knew that this was happening already I might be a
little more comfortable. Or better yet, a integer divide by 65536 would
be the same as moving the the high word into the low word and zeroing
the high word.
> Regards,
> Rob Craig
> Rapid Deployment Software
Thanks for letting me rant about bit-shifting again
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