Re: [Boost-users] About naming of integer log in base 2

Subject: Re: [Boost-users] About naming of integer log in base 2
From: Murilo Adriano Vasconcelos (muriloufg_at_[hidden])
Date: 2010-07-20 10:39:25

Hi,

>
> Maybe, it depends on the relative cost of two: the reason for
> unchecked_factorial is that low-order factorials are often used inside the
> inner loop of a computation, where anything more expensive than a simple
> table lookup is out of the question (and the check can easily be moved
> outside the loop anyway).  Does the same thing apply here.... or is the cost
> of the check trivial compared to the bit manipulations?  I don't know the
> answers to these BTW, just some questions you might want to think about ;-)
>
>
Thank you John!

I thought better and followed Paul's recommendations and implemented
math::policies on ilog2() [0], and also changed the count_leading_zeros(T
value) to return the size in bits of T when value is equal to 0 (all bits
are leading 0's).

So I've added two ifs, but think that the design of the functions are
better.

[0] -
https://svn.boost.org/trac/boost/browser/sandbox/SOC/2010/bits_and_ints/boost/integer/ilog2.hpp?rev=64198

> ilog2 isn't a bad name BTW, John.
>
>
I think ilog2 won.

Best,
-- 
Murilo Adriano Vasconcelos
http://murilo.wordpress.com