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Binary search to find gap that leaves the desired fraction of features

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This commit is contained in:
Eric Fischer 2016-11-02 12:49:31 -07:00
parent faa5720e3b
commit d0db3323fb
3 changed files with 532 additions and 259 deletions
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2
geojson.cpp
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@ -379,7 +379,7 @@ int serialize_geometry(json_object *geometry, json_object *properties, json_obje
sf.tippecanoe_maxzoom = tippecanoe_maxzoom;
sf.geometry = dv;
sf.m = m;
sf.feature_minzoom = 0; // Will be filled in during index merging
sf.feature_minzoom = 0; // Will be filled in during index merging
if (inline_meta) {
sf.metapos = -1;

712
tests/muni/out/-Z11_-z13_-k5000_-as.json
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File diff suppressed because it is too large Load Diff

77
tile.cpp
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@ -1130,6 +1130,44 @@ bool find_common_edges(std::vector<partial> &partials, int z, int line_detail, d
}
}
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;
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 want = indices.size() * f;
while (top - bot > 2) {
long long guess = bot / 2 + top / 2;
size_t count = 0;
for (size_t i = 0; i < indices.size(); i++) {
if (i == 0 || indices[i] < indices[i - 1] || (long long) (indices[i] - indices[i - 1]) > guess) {
count++;
}
}
if (count > want) {
bot = guess;
} else if (count < want) {
top = guess;
} else {
return guess;
}
}
return top;
}
struct write_tile_args {
struct task *tasks;
char *metabase;
@ -1420,9 +1458,7 @@ long long write_tile(FILE *geoms, long long *geompos_in, char *metabase, char *s
}
if (additional[A_INCREASE_SPACING_AS_NEEDED]) {
if (index > merge_previndex) {
indices.push_back(index - merge_previndex);
}
indices.push_back(index);
if (index - merge_previndex < mingap) {
continue;
}
@ -1728,20 +1764,13 @@ long long write_tile(FILE *geoms, long long *geompos_in, char *metabase, char *s
line_detail++; // to keep it the same when the loop decrements it
continue;
} else if (additional[A_INCREASE_SPACING_AS_NEEDED]) {
std::sort(indices.begin(), indices.end());
mingap_fraction = mingap_fraction * 200000.0 / totalsize * 0.95;
size_t n = (indices.size() - 1) * (1 - mingap_fraction);
if (n < indices.size() && mingap < indices[n]) {
mingap = indices[n];
if (mingap > arg->mingap_out) {
arg->mingap_out = mingap;
}
if (!quiet) {
fprintf(stderr, "Going to try keeping the sparsest %0.2f%% of the features to make it fit\n", mingap_fraction * 100.0);
}
line_detail++;
continue;
arg->mingap_out = mingap = choose_mingap(indices, mingap_fraction);
if (!quiet) {
fprintf(stderr, "Going to try keeping the sparsest %0.2f%% of the features to make it fit\n", mingap_fraction * 100.0);
}
line_detail++;
continue;
} else if (prevent[P_DYNAMIC_DROP]) {
fraction = fraction * 200000 / totalsize * 0.95;
if (!quiet) {
@ -1784,19 +1813,12 @@ long long write_tile(FILE *geoms, long long *geompos_in, char *metabase, char *s
}
line_detail++; // to keep it the same when the loop decrements it
} else if (additional[A_INCREASE_SPACING_AS_NEEDED]) {
std::sort(indices.begin(), indices.end());
mingap_fraction = mingap_fraction * max_tile_size / compressed.size() * 0.95;
size_t n = (indices.size() - 1) * (1 - mingap_fraction);
if (n < indices.size() && mingap < indices[n]) {
mingap = indices[n];
if (mingap > arg->mingap_out) {
arg->mingap_out = mingap;
}
if (!quiet) {
fprintf(stderr, "Going to try keeping the sparsest %0.2f%% of the features to make it fit\n", mingap_fraction * 100.0);
}
line_detail++;
arg->mingap_out = mingap = choose_mingap(indices, mingap_fraction);
if (!quiet) {
fprintf(stderr, "Going to try keeping the sparsest %0.2f%% of the features to make it fit\n", mingap_fraction * 100.0);
}
line_detail++;
} else if (prevent[P_DYNAMIC_DROP]) {
// The 95% is a guess to avoid too many retries
// and probably actually varies based on how much duplicated metadata there is
@ -2061,7 +2083,7 @@ int traverse_zooms(int *geomfd, off_t *geom_size, char *metabase, char *stringpo
}
double zoom_gamma = gamma;
double zoom_mingap = 0;
unsigned long long zoom_mingap = 0;
for (size_t pass = start; pass < 2; pass++) {
pthread_t pthreads[threads];
@ -2129,6 +2151,7 @@ int traverse_zooms(int *geomfd, off_t *geom_size, char *metabase, char *stringpo
}
if (args[thread].mingap_out > zoom_mingap) {
zoom_mingap = args[thread].mingap_out;
fprintf(stderr, "bump mingap to %llu\n", zoom_mingap);
}
}
}