performance improvements for decimate

tutorial/703_Decimation/main.cpp

@@ -1,7 +1,9 @@
 #include <igl/circulation.h>
 #include <igl/collapse_edge.h>
 #include <igl/edge_flaps.h>
+#include <igl/decimate.h>
 #include <igl/shortest_edge_and_midpoint.h>
+#include <igl/parallel_for.h>
 #include <igl/read_triangle_mesh.h>
 #include <igl/opengl/glfw/Viewer.h>
 #include <Eigen/Core>
@@ -33,9 +35,8 @@ int main(int argc, char * argv[])
   // Prepare array-based edge data structures and priority queue
   VectorXi EMAP;
   MatrixXi E,EF,EI;
-  typedef std::set<std::pair<double,int> > PriorityQueue;
-  PriorityQueue Q;
-  std::vector<PriorityQueue::iterator > Qit;
+  igl::min_heap< std::tuple<double,int,int> > Q;
+  Eigen::VectorXi EQ;
   // If an edge were collapsed, we'd collapse it to these points:
   MatrixXd C;
   int num_collapsed;
@@ -46,19 +47,28 @@ int main(int argc, char * argv[])
     F = OF;
     V = OV;
     edge_flaps(F,E,EMAP,EF,EI);
-    Qit.resize(E.rows());
-
     C.resize(E.rows(),V.cols());
     VectorXd costs(E.rows());
-    Q.clear();
-    for(int e = 0;e<E.rows();e++)
+    // https://stackoverflow.com/questions/2852140/priority-queue-clear-method
+    // Q.clear();
+    Q = {};
+    EQ = Eigen::VectorXi::Zero(E.rows());
     {
-      double cost = e;
-      RowVectorXd p(1,3);
-      shortest_edge_and_midpoint(e,V,F,E,EMAP,EF,EI,cost,p);
-      C.row(e) = p;
-      Qit[e] = Q.insert(std::pair<double,int>(cost,e)).first;
+      Eigen::VectorXd costs(E.rows());
+      igl::parallel_for(E.rows(),[&](const int e)
+      {
+        double cost = e;
+        RowVectorXd p(1,3);
+        shortest_edge_and_midpoint(e,V,F,E,EMAP,EF,EI,cost,p);
+        C.row(e) = p;
+        costs(e) = cost;
+      },10000);
+      for(int e = 0;e<E.rows();e++)
+      {
+        Q.emplace(costs(e),e,0);
+      }
     }
+
     num_collapsed = 0;
     viewer.data().clear();
     viewer.data().set_mesh(V,F);
@@ -75,8 +85,7 @@ int main(int argc, char * argv[])
       const int max_iter = std::ceil(0.01*Q.size());
       for(int j = 0;j<max_iter;j++)
       {
-        if(!collapse_edge(
-          shortest_edge_and_midpoint, V,F,E,EMAP,EF,EI,Q,Qit,C))
+        if(!collapse_edge(shortest_edge_and_midpoint,V,F,E,EMAP,EF,EI,Q,EQ,C))
         {
           break;
         }