From: Morton Goldberg <m_goldberg@...>
Date: 2007-09-03T11:22:41+09:00
Subject: Re: Bug in % (Float)?

On Sep 2, 2007, at 7:57 PM, Calamitas wrote:

> On 02/09/07, Morton Goldberg <m_goldberg@ameritech.net> wrote:
>> On Sep 2, 2007, at 7:32 AM, Calamitas wrote:
>> I'm not too surprised. It was bound to break for some sufficiently
>> small n;  the discontinuities become denser as n -> 0. My horror over
>> Ruby's (actually I suspect the underlying C math library) result with
>> n = 0.1 is 0.1 is so large. Even 0.00032 is rather a larger n than I
>> would like.
>
> Well, the smallest n for which m_mod_n(1.0, 1.0 / n) is way off is n =
> 93. If it's any consolation though, among the first million n, there
> are only 78161 for which m_mod_n doesn't give something zeroish. There
> are 497886 such n for which Ruby's built-in % is off.

That is a real consolation :)

Seriously, to me, this is the most convincing argument you've come up  
with in support of your position that finding a better method for  
computing % with floats is a lost cause.

<snip>

> Will you let me know what Wolfram Research answers?

Certainly. I'll pass it on directly to your gmail account. It may be  
some time before I get an answer since they are a bit swamped right  
now with problems arising from their new Mathematica 6 release, and  
my query is a minor side-issue from their POV.

Regards, Morton