Bash

git add builder/src/build_index.cpp && git commit --amend --no-edit 2>&1 | tail -1 && cat builder/src/build_index.cpp | ssh node3 "cat > /tmp/traccar-geocoder/builder/src/build_index.cpp" && ssh node3 "cd /tmp/traccar-geocoder/builder/build && make -j\$(nproc) 2>&1 | tail -3" 2>&1

Fix, amend, rebuild


 1 file changed, 17 insertions(+)
      |           ^~~~~~~~
[100%] Linking CXX executable build-index
[100%] Built target build-index


Now test Germany with timers:


ssh node3 "rm -rf /tmp/de-fast && mkdir -p /tmp/de-fast && /tmp/traccar-geocoder/builder/build/build-index /tmp/de-fast ~/pbf/germany.osm.pbf --parallel-admin 2>&1 | grep '\\['" 2>&1

Germany with timers


  [2.0s] Pass 1: relation scanning
  [18.6s] Pass 2: node processing
  [13.4s] Pass 3: way processing
  DEBUG '55546': ways: [w197101541 first=323927596 last=738639324 n=23] [w83390312 first=323540614 last=323927596 n=9] [w103519615 first=323919977 last=323540614 n=18] [w82453211 first=324144479 last=323919977 n=22] [w82854344 first=323737093 last=324144479 n=8] [w82854343 first=323784639 last=323737093 n=7] [w82453274 first=323780057 last=323784639 n=26] [w82854356 first=959665468 last=323780057 n=12] [w82453061 first=323487874 last=959665468 n=2] [w361392255 first=323909831 last=323487874 n=19] [w361478038 first=3658742726 last=323909831 n=3] [w83115016 first=323669620 last=3658742726 n=2] [w83115024 first=323704447 last=323669620 n=13] [w56448456 first=323573335 last=323704447 n=2] [w83115034 first=323909506 last=323573335 n=7] [w82453250 first=323401725 last=323909506 n=5] [w56448464 first=323815636 last=323401725 n=7] [w1483473381 first=323815636 last=707478473 n=12] [w56448380 first=707478473 last=707478654 n=23] [w1483472544 first=3567905940 last=707478654 n=14] [w56448434 first=707478639 last=3567905940 n=28] [w56448471 first=707478639 last=707478477 n=5] [w56448407 first=707478477 last=471546024 n=7] [w528981686 first=471546024 last=1350759928 n=3] [w561236996 first=1350759928 last=1351705259 n=15] [w528981687 first=5139522515 last=1674576244 n=3] [w82825205 first=1674576244 last=707478678 n=19] [w1066405302 first=707478678 last=1675165086 n=2] [w56448447 first=1675165086 last=707478696 n=13] [w458921334 first=4548475758 last=707478696 n=9] [w56448381 first=707478517 last=4548475758 n=2] [w561236986 first=5412056105 last=707478517 n=6] [w56448426 first=707478448 last=5412056105 n=17] [w56448410 first=9792474559 last=707478448 n=3] [w1066405304 first=324139588 last=9792474559 n=3] [w83831219 first=324129352 last=324139588 n=10] [w82854354 first=323433111 last=324129352 n=25] [w1066405307 first=9846633421 last=323433111 n=17] [w29412137 first=323931327 last=9846633421 n=24] [w82854348 first=567185861 last=323931327 n=50] [w58282350 first=323634440 last=567185861 n=13] [w195958923 first=738639324 last=323634440 n=3]
  DEBUG '55543': ways: [w82825295 first=707478661 last=471546024 n=45] [w528981686 first=471546024 last=1350759928 n=3] [w561236996 first=1350759928 last=1351705259 n=15] [w528981687 first=5139522515 last=1674576244 n=3] [w82825205 first=1674576244 last=707478678 n=19] [w1066405302 first=707478678 last=1675165086 n=2] [w56448447 first=1675165086 last=707478696 n=13] [w56448444 first=707478696 last=963915167 n=5] [w1105647627 first=963915167 last=3660345646 n=8] [w1455858600 first=3660345646 last=10117529738 n=3] [w1483477594 first=10117529738 last=10117524960 n=2] [w82825119 first=10117524960 last=963916503 n=21] [w82825081 first=963916503 last=707478661 n=10]
  DEBUG 'Düren': ways: [w438390200 first=428892823 last=4635989132 n=41] [w438397122 first=4635989132 last=4361440131 n=52]
  WARN: relation 'Düren' (level 10, 2 members): 0 rings from 2 ways (  DEBUG 'Derichsweiler': ways: [w438397123 first=4361440131 last=4361440133 n=3] [w564331877 first=5437479801 last=4361440133 n=24]
  DEBUG 'Hehlingen': ways: [w101559114 first=323472371 last=323654339 n=16] [w1447944003 first=323945148 last=323654339 n=18] [w1448056004 first=323945148 last=13285066168 n=78] [w1448056003 first=13285066170 last=13285066176 n=7] [w283748979 first=13285066176 last=13285066239 n=64] [w1465686506 first=13285066239 last=13285066279 n=41] [w1447964139 first=13285066279 last=13285066293 n=15] [w1447964141 first=13285066293 last=13285049425 n=9] [w1466781881 first=13285049425 last=13285049499 n=75] [w101559287 first=13285049499 last=13285066069 n=71] [w1466781877 first=13285066069 last=323472371 n=8]
  DEBUG 'Neuhaus-Reislingen': ways: [w1448056000 first=13286085007 last=324014593 n=34] [w186015071 first=323945148 last=324014593 n=42] [w1448056004 first=323945148 last=13285066168 n=78] [w1448056003 first=13285066170 last=13285066176 n=7] [w1465686504 first=13285066176 last=13286085229 n=33] [w1448056002 first=13286085229 last=13286085123 n=107] [w1448056006 first=13286085123 last=13286085007 n=89]
  [33.3s] Admin assembly
  [31.4s] S2 cell computation
  [3.1s] Deduplication
  [8.7s] Index file writing


Timers work. **Index file writing: 8.7s** (down from 13.1s before optimization — **33% faster**).

Now planet test:


ssh node3 "rm -rf ~/planet-fast && mkdir -p ~/planet-fast && nohup /tmp/traccar-geocoder/builder/build/build-index ~/planet-fast ~/pbf/planet.osm.pbf --parallel-admin > ~/planet-fast.log 2>&1 & echo started" 2>&1

Start planet build with optimized writes


Command running in background with ID: bdspw0sw7. Output is being written to: /tmp/claude-0/-root-traccar-geocoder/af1c4baa-0f9a-4420-a8b3-ce20dc28c8b9/tasks/bdspw0sw7.output


sleep 300 && ssh node3 "grep '\\[' ~/planet-fast.log | head -5" 2>&1

Check after 5 min


  [50.9s] Pass 1: relation scanning
  [179.7s] Pass 2: node processing


sleep 300 && ssh node3 "grep '\\[' ~/planet-fast.log" 2>&1

Check after 5 more min


<persisted-output>
Output too large (850KB). Full output saved to: /root/.claude/projects/-root-traccar-geocoder/af1c4baa-0f9a-4420-a8b3-ce20dc28c8b9/tool-results/bw93uhxt8.txt

Preview (first 2KB):
  [50.9s] Pass 1: relation scanning
  [179.7s] Pass 2: node processing
  [154.7s] Pass 3: way processing
  DEBUG 'Västerhiske': ways: [w457539038 first=220346 last=4536695971 n=5] [w457539037 first=294065990 last=220346 n=2] [w121177158 first=1357160449 last=294065990 n=3] [w457539004 first=1357160453 last=1357160449 n=2] [w28445305 first=312514646 last=1357160453 n=3] [w102156069 first=1983283071 last=312514646 n=3] [w457539035 first=1179039271 last=1983283071 n=2] [w457639802 first=4536695974 last=1179039271 n=4] [w28533849 first=4536695974 last=301742553 n=7] [w457639827 first=4536695971 last=286071787 n=3] [w457639815 first=286071787 last=286071789 n=13] [w26557540 first=286071789 last=286103957 n=9]
  DEBUG 'Katku küla': ways: [w45485188 first=579537007 last=579537014 n=8] [w45485189 first=579537015 last=579537017 n=3] [w45485190 first=579537014 last=579537015 n=9] [w445528618 first=579537029 last=4429409531 n=4] [w445528612 first=4429409531 last=4429409532 n=2] [w445528613 first=4429409532 last=579537026 n=2] [w45485191 first=579537026 last=579537017 n=3] [w45485192 first=579537034 last=579537029 n=4]
  DEBUG 'Koovälja küla': ways: [w45485188 first=579537007 last=579537014 n=8] [w45488494 first=579574029 last=579595441 n=112] [w45488495 first=579595570 last=579595574 n=7] [w45488496 first=579537014 last=579595574 n=8] [w45488498 first=579595593 last=579595592 n=2] [w93247204 first=579595593 last=579595611 n=21] [w45488499 first=579595441 last=579595611 n=2] [w45488500 first=579595625 last=579574029 n=2] [w45488501 first=579595570 last=579595592 n=3]
...
</persisted-output>


Past Pass 3 (154.7s). Admin assembly in progress. Let me wait for the write phase timing.


sleep 600 && ssh node3 "grep '\\[.*s\\]' ~/planet-fast.log" 2>&1

Check after 10 min


  [50.9s] Pass 1: relation scanning
  [179.7s] Pass 2: node processing
  [154.7s] Pass 3: way processing
  [309.7s] Admin assembly


Admin assembly done in 309.7s (5.2 min) — that's slower than the segment branch's 158.7s because we're using the greedy+backtracking approach with retry logic. In S2 cell computation now.


sleep 600 && ssh node3 "grep '\\[.*s\\]' ~/planet-fast.log" 2>&1

Check after 10 more min


  [50.9s] Pass 1: relation scanning
  [179.7s] Pass 2: node processing
  [154.7s] Pass 3: way processing
  [309.7s] Admin assembly
  [1012.9s] S2 cell computation
  [95.2s] Deduplication


S2: 1012.9s, Dedup: 95.2s. Now writing — the phase we optimized.


sleep 120 && ssh node3 "grep '\\[.*s\\]' ~/planet-fast.log; tail -2 ~/planet-fast.log" 2>&1

Check after 2 min


  [50.9s] Pass 1: relation scanning
  [179.7s] Pass 2: node processing
  [154.7s] Pass 3: way processing
  [309.7s] Admin assembly
  [1012.9s] S2 cell computation
  [95.2s] Deduplication
  [95.2s] Deduplication
Writing index files to /home/michtest/planet-fast...


sleep 300 && ssh node3 "grep '\\[.*s\\]' ~/planet-fast.log; tail -2 ~/planet-fast.log; ls ~/planet-fast/ | wc -l" 2>&1

Check after 5 min


  [50.9s] Pass 1: relation scanning
  [179.7s] Pass 2: node processing
  [154.7s] Pass 3: way processing
  [309.7s] Admin assembly
  [1012.9s] S2 cell computation
  [95.2s] Deduplication
  [95.2s] Deduplication
Writing index files to /home/michtest/planet-fast...
2


sleep 300 && ssh node3 "grep '\\[.*s\\]' ~/planet-fast.log; ls ~/planet-fast/ | wc -l" 2>&1

Check after 5 more min


  [50.9s] Pass 1: relation scanning
  [179.7s] Pass 2: node processing
  [154.7s] Pass 3: way processing
  [309.7s] Admin assembly
  [1012.9s] S2 cell computation
  [95.2s] Deduplication
  [577.2s] Index file writing
14


**Planet write phase: 577.2s** (9.6 min) — down from **853.9s** (14.2 min) on the segment branch. That's a **32% speedup** on the write phase.

Full planet timing comparison:

| Phase | Before optimization | After optimization | Improvement |
|---|---|---|---|
| Pass 1: relations | 47.8s | 50.9s | — |
| Pass 2: nodes | 174.4s | 179.7s | — |
| Pass 3: ways | 149.0s | 154.7s | — |
| Admin assembly | 158.7s (segment) / 309.7s (greedy) | 309.7s | — |
| S2 cells | 1016.1s | 1012.9s | — |
| Deduplication | 94.9s | 95.2s | — |
| **Index writing** | **853.9s** | **577.2s** | **32% faster** |
| **Total** | ~41 min | ~40 min | ~2.5 min saved |

The S2 cell computation (1013s = 17 min) is now the biggest bottleneck, taking 42% of total time. The write phase went from 35% to 24% of total. Further optimization would focus on S2 parallelization.


Take a look at S2 cells and index writing to see if there are any further optimisations we can make there


Grep

Computing S2 cells|S2 cell computation|cover_edge|point_to_cell


283:static std::vector<S2CellId> cover_edge(double lat1, double lng1, double lat2, double lng2) {
302:static S2CellId point_to_cell(double lat, double lng) {
798:    S2CellId cell = point_to_cell(lat, lng);
1023:        // Defer S2 cell computation to parallel phase
1054:        // Defer S2 cell computation to parallel phase
2331:                                                // Store coords for later S2 cell computation
2771:        // --- Parallel S2 cell computation for ways and interpolation ---
2774:            std::cerr << "Computing S2 cells for ways with " << num_threads << " threads..." << std::endl;
2799:                                auto edge_cells = cover_edge(n1.lat, n1.lng, n2.lat, n2.lng);
2830:                                auto edge_cells = cover_edge(n1.lat, n1.lng, n2.lat, n2.lng);
2864:            std::cerr << "S2 cell computation complete." << std::endl;
2872:        log_phase("S2 cell computation", _pt);

[Showing results with pagination = limit: 15, offset: 0]


   283→static std::vector<S2CellId> cover_edge(double lat1, double lng1, double lat2, double lng2) {
   284→    S2Point p1 = S2LatLng::FromDegrees(lat1, lng1).ToPoint();
   285→    S2Point p2 = S2LatLng::FromDegrees(lat2, lng2).ToPoint();
   286→
   287→    if (p1 == p2) {
   288→        return {S2CellId(p1).parent(kStreetCellLevel)};
   289→    }
   290→
   291→    std::vector<S2Point> points = {p1, p2};
   292→    S2Polyline polyline(points);
   293→
   294→    S2RegionCoverer::Options options;
   295→    options.set_fixed_level(kStreetCellLevel);
   296→
   297→    S2RegionCoverer coverer(options);
   298→    S2CellUnion covering = coverer.GetCovering(polyline);
   299→    return covering.cell_ids();
   300→}
   301→
   302→static S2CellId point_to_cell(double lat, double lng) {
   303→    return S2CellId(S2LatLng::FromDegrees(lat, lng)).parent(kStreetCellLevel);
   304→}
   305→
   306→// Approximate polygon area in square degrees
   307→static float polygon_area(const std::vector<std::pair<double,double>>& vertices) {
   308→    double area = 0;
   309→    size_t n = vertices.size();
   310→    for (size_t i = 0; i < n; i++) {
   311→        size_t j = (i + 1) % n;
   312→        area += vertices[i].first * vertices[j].second;

static std::vector<S2CellId> cover_edge(double lat1, double lng1, double lat2, double lng2) {
    S2Point p1 = S2LatLng::FromDegrees(lat1, lng1).ToPoint();
    S2Point p2 = S2LatLng::FromDegrees(lat2, lng2).ToPoint();

    if (p1 == p2) {
        return {S2CellId(p1).parent(kStreetCellLevel)};
    }

    std::vector<S2Point> points = {p1, p2};
    S2Polyline polyline(points);

    S2RegionCoverer::Options options;
    options.set_fixed_level(kStreetCellLevel);

    S2RegionCoverer coverer(options);
    S2CellUnion covering = coverer.GetCovering(polyline);
    return covering.cell_ids();
}

static S2CellId point_to_cell(double lat, double lng) {
    return S2CellId(S2LatLng::FromDegrees(lat, lng)).parent(kStreetCellLevel);
}

// Approximate polygon area in square degrees
static float polygon_area(const std::vector<std::pair<double,double>>& vertices) {
    double area = 0;
    size_t n = vertices.size();
    for (size_t i = 0; i < n; i++) {
        size_t j = (i + 1) % n;
        area += vertices[i].first * vertices[j].second;


Now let me see the S2 cell computation loop — the 1013s bottleneck.


  2771→        // --- Parallel S2 cell computation for ways and interpolation ---
  2772→        {
  2773→            log_phase("Admin assembly", _pt);
  2774→            std::cerr << "Computing S2 cells for ways with " << num_threads << " threads..." << std::endl;
  2775→
  2776→            // Each thread builds its own local cell maps, then we merge
  2777→            struct ThreadLocalMaps {
  2778→                std::unordered_map<uint64_t, std::vector<uint32_t>> ways;
  2779→                std::unordered_map<uint64_t, std::vector<uint32_t>> interps;
  2780→            };
  2781→            std::vector<ThreadLocalMaps> thread_maps(num_threads);
  2782→
  2783→            // Process streets in parallel
  2784→            std::cerr << "  Processing " << data.deferred_ways.size() << " street ways..." << std::endl;
  2785→            {
  2786→                std::atomic<size_t> way_idx{0};
  2787→                std::vector<std::thread> threads;
  2788→                for (unsigned int t = 0; t < num_threads; t++) {
  2789→                    threads.emplace_back([&, t]() {
  2790→                        auto& local = thread_maps[t].ways;
  2791→                        while (true) {
  2792→                            size_t i = way_idx.fetch_add(1);
  2793→                            if (i >= data.deferred_ways.size()) break;
  2794→                            const auto& dw = data.deferred_ways[i];
  2795→                            std::unordered_set<uint64_t> cells;
  2796→                            for (uint8_t j = 0; j + 1 < dw.node_count; j++) {
  2797→                                const auto& n1 = data.street_nodes[dw.node_offset + j];
  2798→                                const auto& n2 = data.street_nodes[dw.node_offset + j + 1];
  2799→                                auto edge_cells = cover_edge(n1.lat, n1.lng, n2.lat, n2.lng);
  2800→                                for (const auto& c : edge_cells) {
  2801→                                    cells.insert(c.id());
  2802→                                }
  2803→                            }
  2804→                            for (uint64_t cell_id : cells) {
  2805→                                local[cell_id].push_back(dw.way_id);
  2806→                            }
  2807→                        }
  2808→                    });
  2809→                }
  2810→                for (auto& t : threads) t.join();
  2811→            }
  2812→            std::cerr << "  Street ways done." << std::endl;
  2813→
  2814→            // Process interpolations in parallel
  2815→            std::cerr << "  Processing " << data.deferred_interps.size() << " interpolation ways..." << std::endl;
  2816→            {
  2817→                std::atomic<size_t> interp_idx{0};
  2818→                std::vector<std::thread> threads;
  2819→                for (unsigned int t = 0; t < num_threads; t++) {
  2820→                    threads.emplace_back([&, t]() {
  2821→                        auto& local = thread_maps[t].interps;
  2822→                        while (true) {
  2823→                            size_t i = interp_idx.fetch_add(1);
  2824→                            if (i >= data.deferred_interps.size()) break;
  2825→                            const auto& di = data.deferred_interps[i];
  2826→                            std::unordered_set<uint64_t> cells;
  2827→                            for (uint8_t j = 0; j + 1 < di.node_count; j++) {
  2828→                                const auto& n1 = data.interp_nodes[di.node_offset + j];
  2829→                                const auto& n2 = data.interp_nodes[di.node_offset + j + 1];
  2830→                                auto edge_cells = cover_edge(n1.lat, n1.lng, n2.lat, n2.lng);
  2831→                                for (const auto& c : edge_cells) {
  2832→                                    cells.insert(c.id());
  2833→                                }
  2834→                            }
  2835→                            for (uint64_t cell_id : cells) {
  2836→                                local[cell_id].push_back(di.interp_id);
  2837→                            }
  2838→                        }
  2839→                    });
  2840→                }
  2841→                for (auto& t : threads) t.join();
  2842→            }
  2843→            std::cerr << "  Interpolation ways done." << std::endl;
  2844→
  2845→            // Merge thread-local maps into data
  2846→            std::cerr << "  Merging thread-local results..." << std::endl;
  2847→            for (auto& tm : thread_maps) {
  2848→                for (auto& [cell_id, ids] : tm.ways) {
  2849→                    auto& target = data.cell_to_ways[cell_id];
  2850→                    target.insert(target.end(), ids.begin(), ids.end());
  2851→                }
  2852→                for (auto& [cell_id, ids] : tm.interps) {
  2853→                    auto& target = data.cell_to_interps[cell_id];
  2854→                    target.insert(target.end(), ids.begin(), ids.end());
  2855→                }
  2856→            }
  2857→
  2858→            // Free deferred work items
  2859→            data.deferred_ways.clear();
  2860→            data.deferred_ways.shrink_to_fit();
  2861→            data.deferred_interps.clear();
  2862→            data.deferred_interps.shrink_to_fit();
  2863→
  2864→            std::cerr << "S2 cell computation complete." << std::endl;
  2865→        }
  2866→
  2867→        // Resolve interpolation endpoints
  2868→        std::cerr << "Resolving interpolation endpoints..." << std::endl;
  2869→        resolve_interpolation_endpoints(data);
  2870→

        // --- Parallel S2 cell computation for ways and interpolation ---
        {
            log_phase("Admin assembly", _pt);
            std::cerr << "Computing S2 cells for ways with " << num_threads << " threads..." << std::endl;

            // Each thread builds its own local cell maps, then we merge
            struct ThreadLocalMaps {
                std::unordered_map<uint64_t, std::vector<uint32_t>> ways;
                std::unordered_map<uint64_t, std::vector<uint32_t>> interps;
            };
            std::vector<ThreadLocalMaps> thread_maps(num_threads);

            // Process streets in parallel
            std::cerr << "  Processing " << data.deferred_ways.size() << " street ways..." << std::endl;
            {
                std::atomic<size_t> way_idx{0};
                std::vector<std::thread> threads;
                for (unsigned int t = 0; t < num_threads; t++) {
                    threads.emplace_back([&, t]() {
                        auto& local = thread_maps[t].ways;
                        while (true) {
                            size_t i = way_idx.fetch_add(1);
                            if (i >= data.deferred_ways.size()) break;
                            const auto& dw = data.deferred_ways[i];
                            std::unordered_set<uint64_t> cells;
                            for (uint8_t j = 0; j + 1 < dw.node_count; j++) {
                                const auto& n1 = data.street_nodes[dw.node_offset + j];
                                const auto& n2 = data.street_nodes[dw.node_offset + j + 1];
                                auto edge_cells = cover_edge(n1.lat, n1.lng, n2.lat, n2.lng);
                                for (const auto& c : edge_cells) {
                                    cells.insert(c.id());
                                }
                            }
                            for (uint64_t cell_id : cells) {
                                local[cell_id].push_back(dw.way_id);
                            }
                        }
                    });
                }
                for (auto& t : threads) t.join();
            }
            std::cerr << "  Street ways done." << std::endl;

            // Process interpolations in parallel
            std::cerr << "  Processing " << data.deferred_interps.size() << " interpolation ways..." << std::endl;
            {
                std::atomic<size_t> interp_idx{0};
                std::vector<std::thread> threads;
                for (unsigned int t = 0; t < num_threads; t++) {
                    threads.emplace_back([&, t]() {
                        auto& local = thread_maps[t].interps;
                        while (true) {
                            size_t i = interp_idx.fetch_add(1);
                            if (i >= data.deferred_interps.size()) break;
                            const auto& di = data.deferred_interps[i];
                            std::unordered_set<uint64_t> cells;
                            for (uint8_t j = 0; j + 1 < di.node_count; j++) {
                                const auto& n1 = data.interp_nodes[di.node_offset + j];
                                const auto& n2 = data.interp_nodes[di.node_offset + j + 1];
                                auto edge_cells = cover_edge(n1.lat, n1.lng, n2.lat, n2.lng);
                                for (const auto& c : edge_cells) {
                                    cells.insert(c.id());
                                }
                            }
                            for (uint64_t cell_id : cells) {
                                local[cell_id].push_back(di.interp_id);
                            }
                        }
                    });
                }
                for (auto& t : threads) t.join();
            }
            std::cerr << "  Interpolation ways done." << std::endl;

            // Merge thread-local maps into data
            std::cerr << "  Merging thread-local results..." << std::endl;
            for (auto& tm : thread_maps) {
                for (auto& [cell_id, ids] : tm.ways) {
                    auto& target = data.cell_to_ways[cell_id];
                    target.insert(target.end(), ids.begin(), ids.end());
                }
                for (auto& [cell_id, ids] : tm.interps) {
                    auto& target = data.cell_to_interps[cell_id];
                    target.insert(target.end(), ids.begin(), ids.end());
                }
            }

            // Free deferred work items
            data.deferred_ways.clear();
            data.deferred_ways.shrink_to_fit();
            data.deferred_interps.clear();
            data.deferred_interps.shrink_to_fit();

            std::cerr << "S2 cell computation complete." << std::endl;
        }

        // Resolve interpolation endpoints
        std::cerr << "Resolving interpolation endpoints..." << std::endl;
        resolve_interpolation_endpoints(data);


I see several optimization opportunities:

**S2 Cell Computation (1013s):**

1. **`cover_edge` creates S2 objects per-call** — `S2LatLng::FromDegrees`, `S2Polyline`, `S2RegionCoverer`, `S2CellUnion` are all heap-allocated per edge. For 47.8M ways × ~7 edges/way = ~335M calls. The S2RegionCoverer is especially expensive.

2. **`unordered_set<uint64_t> cells` per way** — allocates/deallocates a hash set for every way.

3. **Thread-local maps use `unordered_map<uint64_t, vector<uint32_t>>`** — millions of hash map insertions with vector growth.

4. **Sequential merge** of thread-local maps at line 2847 — single-threaded.

**Index Writing (577s):**

5. **`write_entries` still iterates 332M sorted cells** with hash lookups into `cell_map` — we improved the output but still do O(n) hash lookups during buffer building.

6. **geo_cells.bin buffer build** is sequential — could be parallelized.

Let me address the biggest wins:


Edit

static std::vector<S2CellId> cover_edge(double lat1, double lng1, double lat2, double lng2) {
    S2Point p1 = S2LatLng::FromDegrees(lat1, lng1).ToPoint();
    S2Point p2 = S2LatLng::FromDegrees(lat2, lng2).ToPoint();

    if (p1 == p2) {
        return {S2CellId(p1).parent(kStreetCellLevel)};
    }

    std::vector<S2Point> points = {p1, p2};
    S2Polyline polyline(points);

    S2RegionCoverer::Options options;
    options.set_fixed_level(kStreetCellLevel);

    S2RegionCoverer coverer(options);
    S2CellUnion covering = coverer.GetCovering(polyline);
    return covering.cell_ids();
}

// Reusable cover_edge that takes an output vector to avoid allocation per call.
// The S2RegionCoverer is expensive to construct — use thread_local to reuse it.
static void cover_edge(double lat1, double lng1, double lat2, double lng2,
                        std::vector<S2CellId>& out) {
    out.clear();
    S2Point p1 = S2LatLng::FromDegrees(lat1, lng1).ToPoint();
    S2Point p2 = S2LatLng::FromDegrees(lat2, lng2).ToPoint();

    if (p1 == p2) {
        out.push_back(S2CellId(p1).parent(kStreetCellLevel));
        return;
    }

    // For a simple edge at a fixed level, we can use a faster approach:
    // walk the cells along the edge instead of full region covering.
    // But S2RegionCoverer with fixed_level is already optimized for this.
    thread_local S2RegionCoverer coverer = []() {
        S2RegionCoverer::Options options;
        options.set_fixed_level(kStreetCellLevel);
        return S2RegionCoverer(options);
    }();

    std::vector<S2Point> points = {p1, p2};
    S2Polyline polyline(points);
    S2CellUnion covering = coverer.GetCovering(polyline);
    out = std::move(covering.cell_ids());
}

// Legacy overload for code that still uses return-by-value
static std::vector<S2CellId> cover_edge(double lat1, double lng1, double lat2, double lng2) {
    std::vector<S2CellId> result;
    cover_edge(lat1, lng1, lat2, lng2, result);
    return result;
}