diff --git a/src/seg/SemExtractor.hpp b/src/seg/SemExtractor.hpp
index 7a519f7..a968dba 100644
--- a/src/seg/SemExtractor.hpp
+++ b/src/seg/SemExtractor.hpp
@@ -5,32 +5,34 @@
 #include <cassert>
 #include <iostream>
 #include <fstream>
+#include <unordered_map>
 
 using sem_array_t = std::array<seg_t, 3>;
+using sem_dict_t = std::unordered_map<seg_t, size_t>;
 
 template<typename Tseg, typename Tsem, typename Chunk>
 class SemExtractor
 {
 public:
-    SemExtractor(const Chunk & sem)
+    explicit SemExtractor(const Chunk & sem)
         :m_sem(sem){}
     void collectVoxel(Coord c, Tseg segid)
     {
         auto sem_label = m_sem[c[0]][c[1]][c[2]];
-        if (m_labels[segid][1] > 0 or sem_label == 0) {
-            return;
+        if (not m_labels.contains(segid)) {
+            m_labels[segid] = sem_dict_t();
         }
-
-        if (m_labels[segid][0] == 0) {
-            m_labels[segid][0] = sem_label;
-        } else if (m_labels[segid][0] != sem_label){
-            m_labels[segid][1] = 1;
+        auto & sem_dict = m_labels[segid];
+        if (sem_dict.contains(sem_label)) {
+            sem_dict[sem_label] += 1;
+        } else {
+            sem_dict[sem_label] = 1;
         }
     }
 
     void collectBoundary(int face, Coord c, Tseg segid) {}
     void collectContactingSurface(int nv, Coord c, Tseg segid1, Tseg segid2) {}
-    const MapContainer<Tseg, sem_array_t> & sem_labels() {
+    const MapContainer<Tseg, sem_dict_t> & sem_labels() {
         return m_labels;
     }
 
@@ -41,13 +43,12 @@ class SemExtractor
         assert(of.is_open());
         for (const auto & [k, v]: m_labels) {
             auto svid = k;
+            auto sem_labels = mapToArray(v);
             if (chunkMap.count(k) > 0) {
                 svid = chunkMap.at(k);
             }
-            if (remapped_labels.count(svid) == 0 or remapped_labels[svid][0] == 0) {
-                remapped_labels[svid] = v;
-            } else if (v[0] > 0 and remapped_labels[svid][0] != v[0]) {
-                remapped_labels[svid][1] = 1;
+            if ((remapped_labels.count(svid) == 0) or (remapped_labels[svid][1] < sem_labels[1])) {
+                    remapped_labels[svid] = sem_labels;
             }
         }
         for (const auto & [k,v] : remapped_labels) {
@@ -57,6 +58,19 @@ class SemExtractor
     }
 
 private:
+    sem_array_t mapToArray(const sem_dict_t & entries) {
+        std::vector<std::pair<seg_t, size_t> > vec(entries.begin(), entries.end());
+        std::sort(vec.begin(), vec.end(), [](const auto & a, const auto & b) {
+            return a.second > b.second;
+        });
+        auto & top = vec[0];
+        auto sum = std::accumulate(vec.begin(), vec.end(), static_cast<size_t>(0),
+                              [](auto partialSum, const auto & element) {
+                                  return partialSum + element.second;
+                              });
+        return  sem_array_t{top.first, top.second, sum};
+    }
+
     void write_sem(auto & io, const auto & k, const auto & v) {
         io.write(reinterpret_cast<const char *>(&k), sizeof(k));
         io.write(reinterpret_cast<const char *>(&v), sizeof(v));
@@ -68,7 +82,7 @@ class SemExtractor
     // dummy, axon, bv, dendrite, glia, soma
     //static constexpr std::array<int, 6> sem_map = {-1,1,2,0,2,-1};
     const Chunk & m_sem;
-    MapContainer<Tseg, sem_array_t> m_labels;
+    MapContainer<Tseg, sem_dict_t> m_labels;
 };