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Make consistent {drop,coalesce}-densest decisions between zooms

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This commit is contained in:
Erica Fischer
2024-07-08 12:04:49 -07:00
parent 31ef904b7a
commit bd1b688f16
6 changed files with 2623 additions and 3522 deletions
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tile.cpp
+18 -65
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@@ -740,48 +740,16 @@ int manage_gap(unsigned long long index, unsigned long long *previndex, double s
}
// This function is called to choose the new gap threshold for --drop-densest-as-needed
// and --coalesce-densest-as-needed. The list that is passed in is the list of indices
// of features that survived the previous gap-choosing, so it first needs to calculate
// and sort the gaps between them before deciding which new gap threshold will satisfy
// the need to keep only the requested fraction of features.
static unsigned long long choose_mingap(std::vector<unsigned long long> const &indices, double f) {
unsigned long long bot = ULLONG_MAX;
unsigned long long top = 0;
// and --coalesce-densest-as-needed.
static unsigned long long choose_mingap(std::vector<unsigned long long> &gaps, double f, unsigned long long existing_gap) {
std::stable_sort(gaps.begin(), gaps.end());
for (size_t i = 0; i < indices.size(); i++) {
if (i > 0 && indices[i] >= indices[i - 1]) {
if (indices[i] - indices[i - 1] > top) {
top = indices[i] - indices[i - 1];
}
if (indices[i] - indices[i - 1] < bot) {
bot = indices[i] - indices[i - 1];
}
}
size_t ix = (gaps.size() - 1) * (1 - f);
while (ix + 1 < gaps.size() && gaps[ix] == existing_gap) {
ix++;
}
size_t want = indices.size() * f;
while (top - bot > 2) {
unsigned long long guess = bot / 2 + top / 2;
size_t count = 0;
unsigned long long prev = 0;
for (size_t i = 0; i < indices.size(); i++) {
if (indices[i] - prev >= guess) {
count++;
prev = indices[i];
}
}
if (count > want) {
bot = guess;
} else if (count < want) {
top = guess;
} else {
return guess;
}
}
return top;
return gaps[ix];
}
// This function is called to choose the new "extent" threshold to try when a tile exceeds the
@@ -1548,7 +1516,8 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
std::map<std::string, layer_features> layers;
std::vector<unsigned long long> indices;
std::vector<unsigned long long> gaps;
size_t gaps_increment = 1;
std::vector<long long> extents;
size_t extents_increment = 1;
std::vector<unsigned long long> drop_sequences;
@@ -1747,18 +1716,8 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
}
}
// Cap the indices, rather than sampling them like extents (areas),
// because choose_mingap cares about the distance between *surviving*
// features, not between *original* features, so we can't just store
// gaps rather than indices to be able to downsample them fairly.
// Hopefully the first 100K features in the tile are reasonably
// representative of the other features in the tile.
const size_t MAX_INDICES = 100000;
if (z <= cluster_maxzoom && cluster_distance != 0) {
if (indices.size() < MAX_INDICES) {
indices.push_back(sf.index);
}
add_sample_to(gaps, sf.index - sf.previndex, gaps_increment, seq);
// This still uses merge_previndex instead of sf.previndex
// because the cluster size in -K is expecting to specify
// distances between points that are subject to dot-dropping,
@@ -1784,10 +1743,8 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
continue;
}
} else if (additional[A_DROP_DENSEST_AS_NEEDED]) {
if (indices.size() < MAX_INDICES) {
indices.push_back(sf.index);
}
if (sf.index - merge_previndex < mingap) {
add_sample_to(gaps, sf.index - sf.previndex, gaps_increment, seq);
if (sf.index - sf.previndex < mingap) {
if (drop_feature_unless_it_can_be_added_to_a_multiplier_cluster(layer, sf, layer_unmaps, multiplier_seq, strategy, drop_rest, arg->attribute_accum)) {
continue;
}
@@ -1795,10 +1752,8 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
} else if (z <= cluster_maxzoom && (additional[A_CLUSTER_DENSEST_AS_NEEDED])) {
// this is now just like coalesce-densest, except that instead of unioning the geometry,
// it averages the point locations
if (indices.size() < MAX_INDICES) {
indices.push_back(sf.index);
}
if (sf.index - merge_previndex < mingap && find_feature_to_accumulate_onto(features, sf, which_serial_feature, layer_unmaps, LLONG_MAX, multiplier_seq)) {
add_sample_to(gaps, sf.index - sf.previndex, gaps_increment, seq);
if (sf.index - sf.previndex < mingap && find_feature_to_accumulate_onto(features, sf, which_serial_feature, layer_unmaps, LLONG_MAX, multiplier_seq)) {
features[which_serial_feature].clustered++;
if (features[which_serial_feature].t == VT_POINT &&
@@ -1818,10 +1773,8 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
continue;
}
} else if (additional[A_COALESCE_DENSEST_AS_NEEDED]) {
if (indices.size() < MAX_INDICES) {
indices.push_back(sf.index);
}
if (sf.index - merge_previndex < mingap && find_feature_to_accumulate_onto(features, sf, which_serial_feature, layer_unmaps, LLONG_MAX, multiplier_seq)) {
add_sample_to(gaps, sf.index - sf.previndex, gaps_increment, seq);
if (sf.index - sf.previndex < mingap && find_feature_to_accumulate_onto(features, sf, which_serial_feature, layer_unmaps, LLONG_MAX, multiplier_seq)) {
coalesce_geometry(features[which_serial_feature], sf);
features[which_serial_feature].coalesced = true;
coalesced_area += sf.extent;
@@ -2402,7 +2355,7 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
continue;
} else if (mingap < ULONG_MAX && (additional[A_DROP_DENSEST_AS_NEEDED] || additional[A_COALESCE_DENSEST_AS_NEEDED] || additional[A_CLUSTER_DENSEST_AS_NEEDED])) {
mingap_fraction = mingap_fraction * max_tile_features / totalsize * 0.90;
unsigned long long mg = choose_mingap(indices, mingap_fraction);
unsigned long long mg = choose_mingap(gaps, mingap_fraction, mingap);
if (mg <= mingap) {
mg = (mingap + 1) * 1.5;
@@ -2509,7 +2462,7 @@ long long write_tile(decompressor *geoms, std::atomic<long long> *geompos_in, ch
line_detail++; // to keep it the same when the loop decrements it
} else if (mingap < ULONG_MAX && (additional[A_DROP_DENSEST_AS_NEEDED] || additional[A_COALESCE_DENSEST_AS_NEEDED] || additional[A_CLUSTER_DENSEST_AS_NEEDED])) {
mingap_fraction = mingap_fraction * scaled_max_tile_size / (kept_adjust * compressed.size()) * 0.90;
unsigned long long mg = choose_mingap(indices, mingap_fraction);
unsigned long long mg = choose_mingap(gaps, mingap_fraction, mingap);
if (mg <= mingap) {
double nmg = (mingap + 1) * 1.5;