From 2a4500a4fe2252bebbaacccc115d8d924b47cce9 Mon Sep 17 00:00:00 2001
From: Nikolai Poperechnyi <n.poperechnyi@gmail.com>
Date: Mon, 11 May 2026 21:34:51 +0300
Subject: [PATCH] fix(routing): penalize missing required breaks in route cost

Signed-off-by: Nikolai Poperechnyi <n.poperechnyi@gmail.com>
---
 cpp/src/routing/route/route.cuh               | 36 ++++++++++++++++++-
 .../tests/routing/test_vehicle_properties.py  | 31 ++++++++++++++++
 2 files changed, 66 insertions(+), 1 deletion(-)

diff --git a/cpp/src/routing/route/route.cuh b/cpp/src/routing/route/route.cuh
index b624acb903..919198f533 100644
--- a/cpp/src/routing/route/route.cuh
+++ b/cpp/src/routing/route/route.cuh
@@ -646,7 +646,24 @@ class route_t {
         orig_route, intra_ejection_indices[n_ejections - 1] + 1, route_length + 1, curr_size);
     }
 
-    // extend for other things later
+    /**
+     * @brief Recomputes the objective and infeasibility cost of the current route.
+     *
+     * Resets the route cost accumulators, invokes cost computation for each active
+     * dimension, and returns the resulting objective and infeasibility costs.
+     *
+     * When both BREAK and TIME dimensions are present, this method also adds an
+     * explicit infeasibility penalty for missing required breaks. A break is treated
+     * as required if its latest time is no later than the vehicle arrival time at
+     * the depot. Any deficit between required breaks and breaks present in the
+     * route is added to the BREAK infeasibility component.
+     *
+     * @param check_single_threaded If true, assert that exactly one warp thread is active.
+     *
+     * @return Tuple of `{objective_cost, infeasibility_cost}` for the route.
+     *
+     * @note Mutates and returns `objective_cost[0]` and `infeasibility_cost[0]`.
+     */
     DI thrust::tuple<objective_cost_t, infeasible_cost_t> compute_cost(
       bool check_single_threaded = true)
     {
@@ -663,6 +680,23 @@ class route_t {
           .compute_cost(this->vehicle_info(), *n_nodes, objective_cost[0], infeasibility_cost[0]);
       });
 
+      // Penalize missing required breaks; the per-dim formula only catches excess.
+      if (dimensions_info().has_dimension(dim_t::BREAK) &&
+          dimensions_info().has_dimension(dim_t::TIME)) {
+        auto vinfo         = this->vehicle_info();
+        const i_t n_breaks = vinfo.num_breaks();
+        if (n_breaks > 0) {
+          const double arrival_at_depot = dimensions.time_dim.departure_forward[*n_nodes] +
+                                          dimensions.time_dim.excess_forward[*n_nodes];
+          i_t required = 0;
+          for (i_t i = 0; i < n_breaks; ++i) {
+            required += (vinfo.break_latest[i] <= arrival_at_depot);
+          }
+          const i_t breaks_present = dimensions.break_dim.breaks_forward[*n_nodes];
+          infeasibility_cost[0][dim_t::BREAK] += max(0.0, required - breaks_present);
+        }
+      }
+
       return thrust::make_tuple(objective_cost[0], infeasibility_cost[0]);
     }
 
diff --git a/python/cuopt/cuopt/tests/routing/test_vehicle_properties.py b/python/cuopt/cuopt/tests/routing/test_vehicle_properties.py
index cdf25291f2..fbfe411dbf 100644
--- a/python/cuopt/cuopt/tests/routing/test_vehicle_properties.py
+++ b/python/cuopt/cuopt/tests/routing/test_vehicle_properties.py
@@ -733,3 +733,34 @@ def test_empty_routes_with_breaks():
         h_route = solution_vehicle_x["route"].to_arrow().to_pylist()
         route_len = len(h_route)
         assert route_len > 3
+
+
+def test_required_break_unreachable_is_infeasible():
+    """The problem is infeasible if required break is unreachable"""
+    coords = np.array(
+        [[0.0, 0.0], [10.0, 0.0], [0.0, 200.0]], dtype=np.float32
+    )
+    diff = coords[:, None] - coords[None, :]
+    matrix = cudf.DataFrame(np.linalg.norm(diff, axis=-1).astype(np.float32))
+
+    dm = routing.DataModel(3, n_fleet=1, n_orders=1)
+    dm.add_cost_matrix(matrix)
+    dm.add_transit_time_matrix(matrix)
+    dm.set_order_locations(cudf.Series([1], dtype=np.int32))
+    dm.set_order_time_windows(
+        cudf.Series([0], dtype=np.int32),
+        cudf.Series([1000], dtype=np.int32),
+    )
+    dm.set_vehicle_time_windows(
+        cudf.Series([0], dtype=np.int32),
+        cudf.Series([1000], dtype=np.int32),
+    )
+    dm.set_break_locations(cudf.Series([2], dtype=np.int32))
+    dm.add_break_dimension(
+        cudf.Series([0], dtype=np.int32),
+        cudf.Series([5], dtype=np.int32),
+        cudf.Series([5], dtype=np.int32),
+    )
+
+    sol = routing.Solve(dm)
+    assert sol.get_status() == 1, "break is unreachable, expected status 1"