On Monday 23 January 2006 20:20, Matt Ingalls wrote:

> is that really true?  when i looked into this [ about 5 years ago! ]
> all i found was some bit-wise operations on index increments for
> oscillators and stuff -- it would be no big deal to replace the bit-wise
> stuff with a modulo or  if statement?

Simply replacing a & with a % is not enough, as the latter cannot
deal with negative numbers correctly, so you need an additional
if statement to fix that. Also, a % is much slower than a &.
An if statement is again not enough, as you need at least two to
wrap negative numbers, and more to deal with the possibility of
a very large index.
In any case, using the & operator is the simplest and fastest
way to wrap any integer value to a 0..N-1 range, as long as
N is an integer power of two.
Additionally, more changes are needed to clean up any tricky code
that assumes in some (often non-obvious) way a power of two or at
least even table size. There are many possibilities for introducing
bugs, something that is best avoided when a release is just about
to be made.


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