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perf: add cached CRS variants and benchmarks #2188

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46 changes: 39 additions & 7 deletions benchmark/crs.dart
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@ Future<void> main() async {
const N = 100000000;

const crs = Epsg3857();
final cachedCrs = Epsg3857Cached();
results.add(await timedRun('Concrete type: ${crs.code}.latLngToXY()', () {
double x = 0;
double y = 0;
Expand All @@ -40,6 +41,20 @@ Future<void> main() async {
}
return x + y;
}));
results.add(await timedRun(
'Concrete type (cached): ${cachedCrs.code}.latLngToXY()',
() {
double x = 0;
double y = 0;
for (int i = 0; i < N; ++i) {
final latlng = LatLng((i % 90).toDouble(), (i % 180).toDouble());
final (cx, cy) = cachedCrs.latLngToXY(latlng, 1);
x += cx;
y += cy;
}
return x + y;
},
));

results.add(await timedRun('Concrete type: ${crs.code}.latLngToOffset()', () {
double x = 0;
Expand All @@ -53,13 +68,30 @@ Future<void> main() async {
return x + y;
}));

const crss = <Crs>[
Epsg3857(),
Epsg4326(),
results.add(await timedRun(
'Concrete type (cached): ${cachedCrs.code}.latLngToOffset()',
() {
double x = 0;
double y = 0;
for (int i = 0; i < N; ++i) {
final latlng = LatLng((i % 90).toDouble(), (i % 180).toDouble());
final p = cachedCrs.latLngToOffset(latlng, 1);
x += p.dx;
y += p.dy;
}
return x + y;
},
));

final crss = <(String, Crs)>[
('EPSG:3857', const Epsg3857()),
('EPSG:3857 (cached)', Epsg3857Cached()),
('EPSG:4326', const Epsg4326()),
('EPSG:4326 (cached)', Epsg4326Cached()),
];

for (final crs in crss) {
results.add(await timedRun('${crs.code}.latLngToXY()', () {
for (final (label, crs) in crss) {
results.add(await timedRun('$label.latLngToXY()', () {
double x = 0;
double y = 0;
for (int i = 0; i < N; ++i) {
Expand All @@ -71,7 +103,7 @@ Future<void> main() async {
return x + y;
}));

results.add(await timedRun('${crs.code}.latlngToPoint()', () {
results.add(await timedRun('$label.latlngToPoint()', () {
double x = 0;
double y = 0;
for (int i = 0; i < N; ++i) {
Expand All @@ -83,7 +115,7 @@ Future<void> main() async {
return x + y;
}));

results.add(await timedRun('${crs.code}.pointToLatLng()', () {
results.add(await timedRun('$label.pointToLatLng()', () {
double x = 0;
double y = 0;
for (int i = 0; i < N; ++i) {
Expand Down
44 changes: 42 additions & 2 deletions lib/src/geo/crs.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -61,10 +61,10 @@ abstract class Crs {
LatLng offsetToLatLng(Offset point, double zoom);

/// Zoom to Scale function.
double scale(double zoom) => 256.0 * math.pow(2, zoom);
double scale(double zoom) => 256.0 * math.pow(2.0, zoom);

/// Scale to Zoom function.
double zoom(double scale) => math.log(scale / 256) / math.ln2;
double zoom(double scale) => math.log(scale / 256.0) / math.ln2;

/// Rescales the bounds to a given zoom value.
Rect? getProjectedBounds(double zoom);
Expand All @@ -85,6 +85,31 @@ abstract class Crs {
}
}

mixin _ScaleCacheMixin on Crs {
double _lastScaleZoom = double.nan;
double _lastScaleValue = double.nan;
double _lastZoomScale = double.nan;
double _lastZoomValue = double.nan;

@override
double scale(double zoom) {
if (zoom == _lastScaleZoom) return _lastScaleValue;
final value = super.scale(zoom);
_lastScaleZoom = zoom;
_lastScaleValue = value;
return value;
}

@override
double zoom(double scale) {
if (scale == _lastZoomScale) return _lastZoomValue;
final value = super.zoom(scale);
_lastZoomScale = scale;
_lastZoomValue = value;
return value;
}
}

/// Internal base class for CRS with a single zoom-level independent transformation.
@immutable
@internal
Expand Down Expand Up @@ -159,6 +184,11 @@ class CrsSimple extends CrsWithStaticTransformation {
);
}

/// Non-const CRS with cached scale/zoom.
class CrsSimpleCached extends CrsSimple with _ScaleCacheMixin {
CrsSimpleCached() : super();
}

/// EPSG:3857, The most common CRS used for rendering maps.
@immutable
class Epsg3857 extends CrsWithStaticTransformation {
Expand Down Expand Up @@ -199,6 +229,11 @@ class Epsg3857 extends CrsWithStaticTransformation {
bool get replicatesWorldLongitude => true;
}

/// Non-const CRS with cached scale/zoom.
class Epsg3857Cached extends Epsg3857 with _ScaleCacheMixin {
Epsg3857Cached() : super();
}

/// EPSG:4326, A common CRS among GIS enthusiasts.
/// Uses simple Equirectangular projection.
@immutable
Expand All @@ -214,6 +249,11 @@ class Epsg4326 extends CrsWithStaticTransformation {
);
}

/// Non-const CRS with cached scale/zoom.
class Epsg4326Cached extends Epsg4326 with _ScaleCacheMixin {
Epsg4326Cached() : super();
}

/// Custom CRS
@immutable
class Proj4Crs extends Crs {
Expand Down