On Wed, Jul 03, 2019 at 10:30:29PM -0700, Mark Begbie wrote:
I totally get that the map updates are getting more complex. I'm
trying to build New Zealand on a Win 10 Core i7 with 8GB of RAM and
struggling.
What I do NOT get at all, is how on the one hand it takes almost a
month to update the map for one group of users and yet for another
group it's done hourly. Something just smells really bad about that.
Not hard to understand at all:
OSM Data for Torrey UT at zoom level 14:
https://www.openstreetmap.org/#map=14/38.3046/-111.4188
OSM Data for a portion of Los Angeles CA also at zoom level 14:
https://www.openstreetmap.org/#map=14/34.0440/-118.2600
Note the significant difference in detail level.
Your i7 w/ 8GB RAM machine would build a map data file for Torrey
UT *much* more quickly than it would build a map data file for Los
Angeles CA. In fact, it likely might build the entire state of Utah
faster than it would build just the city of Los Angeles, much less the
whole state of CA.
So a huge contributor to the speed of map updates is the density of
data to be built (under the reasonable presumption that the OsmAnd
devs. have a single size, likely large, server that is used to build
the updated maps). Areas that are lower density can get built faster
than areas of extreme density for the same size server performing the
build.
As for the hourly builds, they sound like they are built as deltas
against the last monthly build file, so the hourly builds only have to
consume the changes that occurred since the last monthly file was
built, which is a much smaller dataset, no matter the starting area,
than building the whole area from scratch. And OSM itself provides a
service that delivers those changes as just the changes since the last
change file, so OsmAnd does not have to first determine what changed
before building the hourly files.
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