Re: [gnugo-devel] ticket 87, floating point comparison

[Arend Bayer]

Hi Alain,

> http://trac.gnugo.org/gnugo/ticket/87 has been closed as a "won't fix"
> 
> One thing i can do is a fixing patch, replacing all unreliable floating 
> equality test by safe inequality tests:
> if (a == b) 
> replaced by 
> epilon=0.000001
> if (abs(a-b) <= epsilon)
> 
> Should i use gg_abs instead of abs ?

I think it is better for readability to leave it as it is; I have reviewed
the complaints and these comparisons are in fact all safe (*). For example,
consider:

if (q->white_strength[ii] == 0.0)

The array white_strength is initialized to 0. Then some of the fields
are set to some numbers like 100.0 or 60.0. A field that was set to
s.th. non-zero will always compare unequal to zero, whereas s.th. left
unchanged will always compare equal to 0.0.

Arend

(*) With the exception 'if (white_score == black_score)' which only affects
debugging output (and only marginally so).