Distance point <=> straight line in space

Hi,

in a program, I've got a straight line in space defined by two points (p1 and p2) on it, and a set (~ 10000) points q_i in space. Then I need to calculate for each of those points the distance to the straight. At the moment I'm doing it like this:

vector g = normalized (p2 - p1) // Find normalized direction
for i = 1 to n
distance_i = norm (cross_product (p2 - q_i, g))

I believe this formula is fairly straight-forward (a single cross-product and a norm); unfortunatelly, my program spents a large amount of time (~ 95% of total runtime) in this routine and the current duration is unacceptable.

Is there a better approach I could take to do this calculation that requires less operations? The output of gcc -O3 seems already reasonably optimized, i.e., the cross-product and norm calculation is fully inlined. I don't think hand-optimized inline-assembly could help here much, right?

Thanks,
Daniel

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