[mkgmap-dev] Polyline base optimisation

Thu Apr 8 16:11:36 BST 2021

Hi Ticker,

Funny, I would have used Integer.MinValue for maxDx/maxDy to make it less confusing.
Do you have an explanation for the change in size? My understanding is that your patch just skips a test which will never find a better encoding?

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
Gesendet: Donnerstag, 8. April 2021 13:58
An: mkgmap development
Betreff: [mkgmap-dev] Polyline base optimisation

Hi Gerd

If starting with unsigned deltas in polyline encoding, and attempting
to reduce the length by testing reduced x/yBase values, there isn't any
point in testing Base-1, as the normal number of bits will be the same
(added sign bit) and there will be some overflows.

Patch attached to change this - it gives me a very slight reduction in
RGN size and might give a performance improvement (I didn't detect
any).

I've also fixed a couple of log. logic errors and changed minDx/y
initial to 0, which is much less confusing because they are symmetric
with maxDx/y which do use 0.

Ticker