bugfix 2 approximate simplification

Author: Dennis Rohde

setup.py

@@ -80,7 +80,7 @@ def build_extension(self, ext):
 
 setup(
     name='Fred-Frechet',
-    version='1.10.5',
+    version='1.10.6',
     author='Dennis Rohde',
     author_email='[email protected]',
     description='A fast, scalable and light-weight C++ Fréchet distance library, exposed to python and focused on (k,l)-clustering of polygonal curves.',

src/simplification.cpp

@@ -11,11 +11,11 @@ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLI
 #include "simplification.hpp"
 
 Curve Simplification::approximate_minimum_link_simplification(const Curve &pcurve, const distance_t epsilon) {
-    if (Config::verbosity > 1) py::print("ASIMPL: computing approximate minimum link simplification");
+    if (Config::verbosity > 1) py::print("ASIMPL: computing approximate minimum link simplification for curve of complexity ", pcurve.complexity());
     Curve &curve = const_cast<Curve&>(pcurve);
     const curve_size_t complexity = curve.complexity();
 
-    curve_size_t i = 0, j = 0;
+    curve_size_t i = 0, j = 0, low, mid, high;
 
     Curve simplification(curve.dimensions()), segment(2, curve.dimensions());
     simplification.push_back(curve.front());
@@ -28,7 +28,7 @@ Curve Simplification::approximate_minimum_link_simplification(const Curve &pcurv
         j = 0;
         distance = 0;
 
-        if (Config::verbosity > 1) py::print("ASIMPL: computing maximum shortcut starting at ", i);
+        if (Config::verbosity > 1) py::print("ASIMPL: computing maximum length shortcut starting at ", i);
 
         if (Config::verbosity > 1) py::print("ASIMPL: exponential error search");
 
@@ -44,27 +44,30 @@ Curve Simplification::approximate_minimum_link_simplification(const Curve &pcurv
             distance = Frechet::Continuous::distance(curve, segment).value;
         }
 
-        curve_size_t low, mid, high;
-        
-        low = j == 1 ? 0 : std::pow(2, j - 1);
+        low = std::pow(2, j - 1);
         high = std::min(static_cast<curve_size_t>(std::pow(2, j)), complexity - i - 1);
 
-        if (Config::verbosity > 1) py::print("ASIMPL: binary error search");
+        if (Config::verbosity > 1) py::print("ASIMPL: binary error search for low = ", low, " and high = ", high);
+        
         while (low < high) {
-            mid = std::ceil((low + high) / 2.);
+            mid = std::ceil(low + (high - low) * .5);
 
             curve.reset_subcurve();
             segment[1] = curve[i + mid];
             curve.set_subcurve(i, i + mid);
 
             distance = Frechet::Continuous::distance(curve, segment).value;
 
-            if (distance <= epsilon) low = mid;
-            else high = mid - 1;
+            if (distance > epsilon) high = mid - 1;
+            else low = mid;
         }
+        
         if (Config::verbosity > 1) py::print("ASIMPL: shortcutting from ", i, " to ", i+low);
+        
         i += low;
+        
         curve.reset_subcurve();
+        
         simplification.push_back(curve[i]);
     }
     return simplification;