From: ptkwt@... (Phil Tomson)
Date: 2005-02-09T23:00:08+09:00
Subject: Re: math changes from 1.8.1 to 1.8.2?(G4's fault?)

In article <20050209114012.F3646D50.ocean@m2.ccsnet.ne.jp>,
H.Yamamoto <ocean@m2.ccsnet.ne.jp> wrote:
>Hello.
>
>ptkwt@aracnet.com (Phil Tomson) wrote:
>(2005/02/08 19:00)
>
>>>fp = FixedPt.new(Math.exp(-5),18,18)
>>>
>>>Which defines an 18bit register with the binary point at bit 18 and stuffs 
>>>the result of Math.exp(-5) into it (shifting the result to the left 18 
>>>times).
>>>
>>>fp.to_f #=> 0.00673675537109375
>>>fp.raw  #=> 1766  
>>>fp.to_i #=> 0
>
>>I loaded up 1.8.2 on my powerbook last night and had the same problem 
>>(which doesn't exist on the Pentium IV).  I suspect it's a difference in 
>>the FPU between the G4 and PIV.  I'm doing lots of summations and 
>>conversions between floating point and fixed point, so I suspect it's the 
>>fault of the G4's FPU..... unless someone else has any other theories.
>
>Interesting. Can I see the code of FixedPt?

To see the problem, I suspect you'll need more than the FixedPt class.  
You'll probably also need the entire application.  It's a support vector 
machine implementation (kind of like a neural network). I could send it to 
you in a tar file if you wish.

Phil