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GEOSEARCH BYBOX: Reduce wastefull computation on geohashGetDistanceIfInRectangle and geohashGetDistance (#11535)

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Optimize geohashGetDistanceIfInRectangle when there are many misses.
It calls 3x geohashGetDistance. The first 2 times we call them to produce intermediate results.
This PR focus on optimizing for those 2 intermediate results.

1 Reduce expensive computation on intermediate geohashGetDistance with same long
2 Avoid expensive lon_distance calculation if lat_distance fails beforehand

Co-authored-by: Oran Agra <oran@redislabs.com>
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filipe oliveira 2022-11-24 16:09:56 +00:00 committed by GitHub
parent ca174e1d47
commit ae1de54900
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1 changed files with 13 additions and 4 deletions
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17
src/geohash_helper.c
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@ -225,8 +225,12 @@ double geohashGetDistance(double lon1d, double lat1d, double lon2d, double lat2d
lon2r = deg_rad(lon2d); lon2r = deg_rad(lon2d);
u = sin((lat2r - lat1r) / 2); u = sin((lat2r - lat1r) / 2);
v = sin((lon2r - lon1r) / 2); v = sin((lon2r - lon1r) / 2);
return 2.0 * EARTH_RADIUS_IN_METERS * double a = u * u;
asin(sqrt(u * u + cos(lat1r) * cos(lat2r) * v * v)); /* if v == 0 we can avoid doing expensive math */
if (v != 0.0){
a += cos(lat1r) * cos(lat2r) * v * v;
}
return 2.0 * EARTH_RADIUS_IN_METERS * asin(sqrt(a));
} }
int geohashGetDistanceIfInRadius(double x1, double y1, int geohashGetDistanceIfInRadius(double x1, double y1,
@ -253,9 +257,14 @@ int geohashGetDistanceIfInRadiusWGS84(double x1, double y1, double x2,
*/ */
int geohashGetDistanceIfInRectangle(double width_m, double height_m, double x1, double y1, int geohashGetDistanceIfInRectangle(double width_m, double height_m, double x1, double y1,
double x2, double y2, double *distance) { double x2, double y2, double *distance) {
double lon_distance = geohashGetDistance(x2, y2, x1, y2); /* latitude distance is less expensive to compute than longitude distance
* so we check first for the latitude condition */
double lat_distance = geohashGetDistance(x2, y2, x2, y1); double lat_distance = geohashGetDistance(x2, y2, x2, y1);
if (lon_distance > width_m/2 || lat_distance > height_m/2) { if (lat_distance > height_m/2) {
return 0;
}
double lon_distance = geohashGetDistance(x2, y2, x1, y2);
if (lon_distance > width_m/2) {
return 0; return 0;
} }
*distance = geohashGetDistance(x1, y1, x2, y2); *distance = geohashGetDistance(x1, y1, x2, y2);