Warp wrote:

>   Perhaps you shouldn't rely on the ability of the compiler to realize
> that the exact same sqrt() is being performed here, and instead calculate
> it only once into a variable. That way you remove the risk of the
> code actually calculating the slow sqrt() twice for no reason.
> 

Good point, thanks for the suggestion. I checked the assembly output and
g++ produces better results with a temporary variable. Less code and
less jumps. Few questions:

1. I understand that sqrtsd takes the square root. What does "call sqrt"
do? Calls a subroutine called "sqrt"? Why on earth are they both needed?
The version with temp variable used one "call sqrt" and the original
version used 2 calls. And both had one sqrtsd.

2. What does "ucomisd %xmm0, %xmm0" effectively do? It compares the same
register.

(Last time I really programmed assembly was 10 years ago when I did a
burning flame demo program..."


Anyway, this was the best version:

        double halfChord = sqrt(halfChord2);

        double a = nearestPointDistance - halfChord;
        if(a > EPSILON)
            return a;
        else
            return nearestPointDistance + halfChord;

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