Performance profiling results

mapbox / vector-tile-cs

Parses vector tiles with C#.

BSD 3-Clause "New" or "Revised" License

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Performance profiling results #29

Open brnkhy opened 7 years ago

brnkhy commented 7 years ago

I was testing my own changes&performance and decided to share this as well.

2017-03-30_00-16-04

This frame took 981ms GetFeature takes 153 of that. Few things to note;

First of all, I thought we were using clipper for 16+ levels. It seems like it's working at 16 as well? Do we need it at 16- levels?
Yes it's mostly clipper but still there are bunch of easy improvements for slow days
Where & Select, or let's say linq in general, little slow and makes probably unnecessary allocations
List size changes are actually costly, I haven't checked this one but at my side, I started calculating the size and creating them with that size which saved me from all those array copying.
ToList is extremely slow. And it's even following a select statement (for tags). Is ConvertAll slower? (I couldn't re-test as profiler is actually quite slow in deep-profile mode)

I'll post if I can find anything else!

cc @BergWerkGIS

wilhelmberg commented 7 years ago

First of all, I thought we were using clipper for 16+ levels. It seems like it's working at 16 as well?

No, usage of clipper is based on the buffer parameter passed to eg GetFeature() or ToGeoJson().

Passing any not-null value triggers clipper. We currently pass 0.

Do we need it at 16- levels?

Yes, with the current implementation of the mapbox-unity-sdk (no feature filtering or feature de-duping across tile borders) it is needed to prevent duplicates features.

All vector tiles z0 -> zMax contain data that extends beyond the actual tile borders.

You could speed things up a bit (10-30% depending on the data of the vt) by passing validate = false here or here.

With validate = false some extensive checks if the tile itself and its data is valid are skipped.

brnkhy commented 7 years ago

@BergWerkGIS is mapbox data always valid?

wilhelmberg commented 7 years ago

@brnkhy

is mapbox data always valid?

😄 yes it should always be valid. I've enabled the validate flag as default mainly for data from other sources that users known what's going and don't think the this library is faulty.

brnkhy commented 7 years ago

@BergWerkGIS ah I see, it's good to know though as it's small but yet another point of perf improvement when someone asks. I know these are quite small compared to mesh gen performance issues but still it's good to keep track ;)