fix

src/nano_fmm/network.cpp

@@ -104,7 +104,7 @@ FlatGeobuf::PackedRTree &Network::rtree() const
         auto &polyline = pair.second.polyline();
         for (int64_t seg_idx = 0, N = polyline.rows(); seg_idx < N - 1;
              ++seg_idx) {
-            auto index = std::make_pair(poly_idx, seg_idx);
+            IndexIJ index(poly_idx, seg_idx);
             seg2idx_[index] = segs_.size();
             segs_.push_back(index);
             double x0 = polyline(seg_idx, 0);

src/nano_fmm/network.hpp

@@ -58,8 +58,8 @@ struct Network
     std::shared_ptr<Config> config_;
 
     // spatial index
-    mutable std::vector<std::pair<int64_t, int64_t>> segs_;
-    mutable std::unordered_map<std::pair<int64_t, int64_t>, size_t> seg2idx_;
+    mutable std::vector<IndexIJ> segs_;
+    mutable std::unordered_map<IndexIJ, size_t, hash_eigen<IndexIJ>> seg2idx_;
     mutable std::optional<FlatGeobuf::PackedRTree> rtree_;
     FlatGeobuf::PackedRTree &rtree() const;
 };

src/nano_fmm/types.hpp

@@ -18,5 +18,21 @@ using RowVectorsNx3 = RowVectors;
 using RowVectorsNx2 = Eigen::Matrix<double, Eigen::Dynamic, 2, Eigen::RowMajor>;
 
 using VectorUi64 = Eigen::Matrix<uint64_t, Eigen::Dynamic, 1>;
+using IndexIJ = Eigen::Matrix<int64_t, 1, 2>;
+using IndexIJK = Eigen::Matrix<int64_t, 1, 3>;
 
+// https://github.com/isl-org/Open3D/blob/179886dfd57797b2b0d379062387c60313a58b2b/cpp/open3d/utility/Helper.h#L71
+template <typename T> struct hash_eigen
+{
+    std::size_t operator()(T const &matrix) const
+    {
+        size_t hash_seed = 0;
+        for (int i = 0; i < (int)matrix.size(); i++) {
+            auto elem = *(matrix.data() + i);
+            hash_seed ^= std::hash<typename T::Scalar>()(elem) + 0x9e3779b9 +
+                         (hash_seed << 6) + (hash_seed >> 2);
+        }
+        return hash_seed;
+    }
+};
 } // namespace nano_fmm