SV: [ODE] Iterative solution

[Martin C. Martin]

Russ Smith wrote:
> 
> as far as constraint order goes, i'm not convinced it makes any
> difference (but i've not verified it one way or the other).

Imagine a stack of boxes sitting on the ground.  First you apply gravity,
so they all fall a little bit and the bottom one goes through the ground. 
If you process them bottom -> top, then the bottom one will be moved up so
it sits on the ground and intersects the 2nd lowest.  Then the lowest will
be moved down and the 2nd up, then the 2nd down and the 3rd up, etc. 
Although the magnitudes will decrease as you go up, you'll get net upward
movement in all boxes in one iteration.

Instead, if you did all the odd boxes then all the even boxes, it would
take many iterations for the bottom box to communicate with the top box. 
So the order can drastically affect the "speed of sound" of the system.

- Martin