Sure, if the ring size is a power of two, and a is greater than or equal to 0, then
a `mod` ringSize == a .&. (ringSize - 1)
that is:
a `mod` 8 == a .&. 7
a `mod` 256 == a .&. 255
etc.
On 11/13/07, Justin Bailey <jgbailey@gmail.com> wrote:
On Nov 13, 2007 2:21 PM, Ryan Ingram <ryani.spam@gmail.com> wrote:
> Never mind, I realized this is a ring buffer with `mod` s. That's another
> slow operation when you're doing code as tight as this. If you can
> guarantee the ring is a power of 2 in size you can use a mask instead, or
> use my original suggestion of deriving rules from the previous rule and the
> new bit; the initial state is determined by the last bits in the buffer and
> you never wrap.
I can't guarantee the ring is a power of 2 but do you feel like
explaining the mask suggestion anyways?
Thanks for the bits suggestion - I'll see if that helps performance at
all. It looks like you have to be very careful in which concrete type
you choose or you'll get a lot of conversion going on.
Justin