Heuristic for bottleneck: estimate on sampled diagram

Sample input diagrams and use the distance between samples as initial guess
in binary search.

Relevant variables:
bottleneck_dist.cpp:10 useSamplingHeur (if false, heuristic is never applied)
bottleneck_dist.cpp:11 heurThreshold (heuristic is not applid to diagrams with
        fewer points)
TODO: add command-line parameters instead

Sampling strategy: sort points by multiplicity, set cutting value to be
the multiplicity where the increase of the next one is maximal and only keep
points whose multiplicity is less then the cutting value

1 files changed, 10 insertions, 1 deletions

diff --git a/geom_bottleneck/example/bottleneck_dist.cpp b/geom_bottleneck/example/bottleneck_dist.cpp
index 655de44..b27bdbb 100644
--- a/geom_bottleneck/example/bottleneck_dist.cpp
+++ b/geom_bottleneck/example/bottleneck_dist.cpp
@@ -6,6 +6,11 @@
 
 typedef std::vector<std::pair<double, double>>  PairVector;
 
+// estimate initial guess on sampled diagram?
+constexpr bool useSamplingHeur = false;
+// if diagrams contain fewer points, don't use heuristic
+constexpr int heurThreshold = 30000;
+
 int main(int argc, char* argv[])
 {
     if (argc < 3 ) {
@@ -29,7 +34,11 @@ int main(int argc, char* argv[])
         // return approximate distance (faster)
         double approxEpsilon =  atof(argv[3]);
         if (approxEpsilon > 0.0) {
-            res = geom_bt::bottleneckDistApprox(diagramA, diagramB, approxEpsilon);
+            if (useSamplingHeur && diagramA.size() > heurThreshold && diagramB.size() > heurThreshold) {
+                res = geom_bt::bottleneckDistApproxHeur(diagramA, diagramB, approxEpsilon);
+            } else {
+                res = geom_bt::bottleneckDistApprox(diagramA, diagramB, approxEpsilon);
+            }
         } else if (approxEpsilon == 0.0) {
             res = geom_bt::bottleneckDistExact(diagramA, diagramB, decPrecision);
         } else {