It works fine the way I explained it on my PC and my implementation. I am not interested in Kangaroo and never refer to it.
Here is the TEMPLATE for you.
Thx for the template, but I already use that in my PointsBuilder demo.
I think you misunderstood my point though. This batch addition that computes both P + Q and P - Q has no usefulness outside BSGS or simply building that specific array of results.
It simply slows down the processing, since there is nothing useful for having both of those points computed. Maybe you should read again what Akito was asking, but more carefully. The answer to his question is that having a DP obtained via P - Q will never be hit, since the pseudo-random walk ends (the point is not used). RC does use it though, but not always.
And for rho or Kangaroo, you always, always need the Y coordinate, because it's needed to actually do the next jump. So your "let's only compute X" is useless for this case.