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Reduce tile-join overzooming memory usage (#162)

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* 16 bits is enough for tile numbers

* Revert "16 bits is enough for tile numbers"

This reverts commit 71a0c4e1cf.

* Check what child tiles each overzoomed tile will have

and don't queue further overzooming of empty tiles

* Clean up naming; use std::move to avoid copying large arrays
This commit is contained in:
Erica Fischer
2023-11-08 12:51:28 -08:00
committed by GitHub
parent 2c56187530
commit d359461e61
6 changed files with 56 additions and 13 deletions
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tile-join.cpp
+19 -6
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@@ -434,7 +434,8 @@ struct tileset_reader {
// for overzooming
int maxzoom_so_far = -1;
std::vector<std::pair<unsigned, unsigned>> tiles_at_maxzoom_so_far;
std::vector<std::pair<unsigned, unsigned>> overzoomed_tiles;
std::vector<std::pair<unsigned, unsigned>> overzoomed_tiles; // tiles at `zoom`
std::vector<std::pair<unsigned, unsigned>> next_overzoomed_tiles; // tiles at `zoom + 1`
bool overzoom_consumed_at_this_zoom = false;
// parent tile cache
@@ -642,12 +643,24 @@ struct tileset_reader {
long long scale = (1LL << zoom) / (1LL << maxzoom_so_far);
for (auto const &xy : tiles_at_maxzoom_so_far) {
for (long long xx = 0; xx < scale; xx++) {
for (long long yy = 0; yy < scale; yy++) {
overzoomed_tiles.push_back(std::pair<unsigned, unsigned>(xy.first * scale + xx, xy.second * scale + yy));
// If this is the first overzoomed level, we don't know yet
// which tiles will be useful, so spell out all 4 child tiles
// from each parent tile.
//
// If it is further overzoomed than that, we have a list of
// which child tiles will have features in them, so use that.
if (zoom == maxzoom_so_far + 1) {
for (auto const &xy : tiles_at_maxzoom_so_far) {
for (long long xx = 0; xx < scale; xx++) {
for (long long yy = 0; yy < scale; yy++) {
overzoomed_tiles.push_back(std::pair<unsigned, unsigned>(xy.first * scale + xx, xy.second * scale + yy));
}
}
}
} else {
overzoomed_tiles = std::move(next_overzoomed_tiles);
next_overzoomed_tiles.clear();
}
std::sort(overzoomed_tiles.begin(), overzoomed_tiles.end(), tilecmp);
@@ -769,7 +782,7 @@ struct tileset_reader {
}
if (source.layers.size() != 0) {
std::string ret = overzoom(source, parent_tile.z, parent_tile.x, parent_tile.y, tile.z, tile.x, tile.y, -1, buffer, std::set<std::string>(), false);
std::string ret = overzoom(source, parent_tile.z, parent_tile.x, parent_tile.y, tile.z, tile.x, tile.y, -1, buffer, std::set<std::string>(), false, &next_overzoomed_tiles);
return ret;
}