Skip some impossible act ends in optimiser

src/optimiser.cpp

@@ -164,8 +164,8 @@ Optimiser::try_previous_best_subpaths(CacheKey key, const Cache& cache,
 // point.
 class PointPtrRangeSet {
 private:
-    const PointPtr m_start;
-    const PointPtr m_end;
+    PointPtr m_start;
+    PointPtr m_end;
     PointPtr m_min_absent_ptr;
     std::vector<PointPtr> m_abnormal_elements;
 
@@ -230,6 +230,7 @@ Optimiser::CacheValue Optimiser::find_best_subpaths(CacheKey key, Cache& cache,
 
     std::vector<std::tuple<ProtoActivation, CacheKey>> acts;
     PointPtrRangeSet attained_act_ends {key.point, m_song->points().cend()};
+    auto lower_bound_set = false;
     auto best_score_boost = 0;
 
     for (auto p = key.point; p < m_song->points().cend(); ++p) {
@@ -261,6 +262,20 @@ Optimiser::CacheValue Optimiser::find_best_subpaths(CacheKey key, Cache& cache,
             }
             break;
         }
+        // This skips some points that are too early to be an act end for the
+        // earliest possible activation.
+        if (!lower_bound_set) {
+            const Measure act_length {8.0 * std::max(sp_bar.min(), 0.5)};
+            const auto earliest_act_end = starting_pos.measure + act_length;
+            auto earliest_pt_end = std::find_if_not(
+                std::next(p), m_song->points().cend(), [&](const auto& pt) {
+                    return pt.hit_window_end.measure <= earliest_act_end;
+                });
+            --earliest_pt_end;
+            attained_act_ends
+                = PointPtrRangeSet {earliest_pt_end, m_song->points().cend()};
+            lower_bound_set = true;
+        }
         for (auto q = attained_act_ends.lowest_absent_element();
              q < m_song->points().cend();) {
             if (attained_act_ends.contains(q)) {