[Patch] SimplifyWayAction optimizations.

[shinigami]

I suppose it is not problem in common use case, but this action is used by OpenData plugin, where it is called for every loaded (sometimes very long) way.

It seems that delNodes and newNodes (in simplifyWay) often contains same data. Problem is that in such case AbstractSet.removeAll is processed as repetitive scanning of given collection and it leads to o(n^{2) complexity.}

Another big slowdown is counting of node frequency in method isRequiredNode, it iterates all way for every node. Simple precounted histogram of nodes makes it much faster.

[Don-vip]

Thanks, some questions:

• can you please share the dataset showing the slowdown?
• how much is is faster?
• did you test with java 9?

[shinigami]

One of sets is ​http://efele.net/maps/tz/world/tz_world.zip - borders of all timezones.
I measured time of OsmImporter.createLayer, it id ~4x faster now.

Other data I used to test are borders of countries extracted from OSM, one multipolygon for one country.
OsmImporter.createLayer takes about 16s now, did not measure it before, but it was enough to have
a lunch:).

Both were measured with latest jdk8.

[shinigami]

One little update yet - two invocations of cos(lat2) extracted to variable.

[GerdP]

Please check. I tried your patches with r14469 and found no improvement in performance with tz_world.zip. I assume the changes in r13540 helped already.