Efficient way of finding distance between two 3D points

Question

I am writing a code in C++ and want to compute distance between two points. Question 1:

I have two points P(x1, y1, z1) and Q(x2, y2, z2) , where x, y and z are floats/doubles.

I want to find the distance between these two points. One way to do it is :

square_root(x_diffx_diff + y_diffy_diff + z_diff*z_diff)

But this is probably not the most efficient way . (e.g. a better formula or a ready made utility in math.h etc )

Question 2:

Is there a better way if I just want to determine if P and Q are in fact the same points?

My inputs are x, y and z coordinates of both the points.

Thank you

Answer 1

Do you need the actual distance? You could use the distance squared to determine if they are the same, and for many other purposes. (saves on the sqrt operation)