backend/src/utils/optimizer.py

@@ -59,20 +59,25 @@ class Optimizer:
 
     def init_ub_time(self, prob: pl.LpProblem, x: pl.LpVariable, L: int, landmarks: list[Landmark], max_time: int):
         """
-        Initialize the objective function coefficients and inequality constraints.
+        Initialize the objective function and inequality constraints for the linear program.
-        -> Adds 1 row of constraints
-        -> Pre-allocates A_ub for the rest of the computations with L + (L*L-L)/2 rows
 
-        This function computes the distances between all landmarks and stores
+        This function sets up the objective to maximize the attractiveness of visiting landmarks,
-        their attractiveness to maximize sightseeing. The goal is to maximize 
+        while ensuring that the total time (including travel and visit duration) does not exceed
-        the objective function subject to the constraints A*x < b and A_eq*x = b_eq.
+        the maximum allowed time. It calculates the pairwise travel times between landmarks and
+        incorporates visit duration to form the inequality constraints.
+
+        The objective is to maximize sightseeing by selecting the most attractive landmarks within
+        the time limit.
 
         Args:
-            landmarks (list[Landmark]): List of landmarks.
+            prob (pl.LpProblem): The linear programming problem where constraints and the objective will be added.
-            max_time (int): Maximum time of visit allowed.
+            x (pl.LpVariable): A decision variable representing whether a landmark is visited.
+            L (int): The number of landmarks.
+            landmarks (list[Landmark]): List of landmarks to visit.
+            max_time (int): Maximum allowable time for sightseeing, including travel and visit duration.
 
         Returns:
-            tuple[list[float], list[float], list[int]]: Objective function coefficients, inequality
+            None: Adds the objective function and constraints to the LP problem directly.
             constraint coefficients, and the right-hand side of the inequality constraint.
         """
         L = len(landmarks)
@@ -117,14 +122,20 @@ class Optimizer:
 
     def respect_number(self, prob: pl.LpProblem, x: pl.LpVariable, L: int, max_landmarks: int):
         """
-        Generate constraints to ensure each landmark is visited only once and cap the total number of visited landmarks.
+        Generate constraints to ensure each landmark is visited at most once and cap the total number of visited landmarks.
-        -> Adds L-1 rows of constraints
+
+        This function adds the following constraints to the linear program:
+        1. Each landmark is visited at most once by creating L-2 constraints (one for each landmark).
+        2. The total number of visited landmarks is capped by the specified maximum number (`max_landmarks`) plus 2.
 
         Args:
-            L (int): Number of landmarks.
+            prob (pl.LpProblem): The linear programming problem where constraints will be added.
+            x (pl.LpVariable): Decision variable indicating whether a landmark is visited.
+            L (int): The total number of landmarks.
+            max_landmarks (int): The maximum number of landmarks that can be visited.
 
         Returns:
-            tuple[np.ndarray, list[int]]: Inequality constraint coefficients and the right-hand side of the inequality constraints.
+            None: This function directly modifies the `prob` object by adding constraints.
         """
         # L-2 constraints: each landmark is visited exactly once
         for i in range(1, L-1):
@@ -137,16 +148,20 @@ class Optimizer:
     def break_sym(self, prob: pl.LpProblem, x: pl.LpVariable, L: int):
         """
         Generate constraints to prevent simultaneous travel between two landmarks
-        in both directions. Constraint to not have d14 and d41 simultaneously. 
+        in both directions. This constraint ensures that, for any pair of landmarks,
-        Does not prevent cyclic paths with more elements
+        travel from landmark i to landmark j (dij) and travel from landmark j to landmark i (dji)
-        -> Adds (L*L-L)/2 rows of constraints (some of which might be zero)
+        cannot happen simultaneously.
+
+        This method adds constraints to break symmetry, specifically to prevent
+        cyclic paths with only two elements. It does not prevent cyclic paths involving more than two elements.
 
         Args:
-            L (int): Number of landmarks.
+            prob (pl.LpProblem): The linear programming problem where constraints will be added.
+            x (pl.LpVariable): Decision variable representing travel between landmarks.
+            L (int): The total number of landmarks.
 
         Returns:
-            tuple[np.ndarray, list[int]]:   Inequality constraint coefficients and 
+            None: This function modifies the `prob` object by adding constraints in-place.
-                                            the right-hand side of the inequality constraints.
         """
         upper_ind = np.triu_indices(L, 0, L)  # Get the upper triangular indices
         up_ind_x = upper_ind[0]
@@ -161,15 +176,20 @@ class Optimizer:
 
     def init_eq_not_stay(self, prob: pl.LpProblem, x: pl.LpVariable, L: int):
         """
-        Generate constraints to prevent staying in the same position (e.g., removing d11, d22, d33, etc.).
+        Generate constraints to prevent staying at the same position during travel. 
-        -> Adds 1 row of constraints
+        Specifically, it removes travel from a landmark to itself (e.g., d11, d22, d33, etc.).
-        -> Pre-allocates A_eq for the rest of the computations with (L+ 2 + dynamic incr) rows
+
+        This function adds one equality constraint to the optimization problem that ensures 
+        no decision variable corresponding to staying at the same landmark is included 
+        in the solution. This helps in ensuring that the path does not include self-loops.
 
         Args:
-            L (int): Number of landmarks.
+            prob (pl.LpProblem): The linear programming problem where constraints will be added.
+            x (pl.LpVariable): Decision variable representing travel between landmarks.
+            L (int): The total number of landmarks.
 
         Returns:
-            tuple[list[np.ndarray], list[int]]: Equality constraint coefficients and the right-hand side of the equality constraints.
+            None: This function modifies the `prob` object by adding an equality constraint in-place.
         """
         A_eq = np.zeros((L, L), dtype=np.int8)
 
@@ -181,18 +201,23 @@ class Optimizer:
         prob += (pl.lpSum([A_eq[j] * x[j] for j in range(L*L)]) == 0)
 
 
-    # Constraint to ensure start at start and finish at goal
     def respect_start_finish(self, prob: pl.LpProblem, x: pl.LpVariable, L: int):
         """
         Generate constraints to ensure that the optimization starts at the designated 
         start landmark and finishes at the goal landmark.
-        -> Adds 3 rows of constraints
+
+        Specifically, this function adds three equality constraints:
+        1. Ensures that the path starts at the designated start landmark (row 0).
+        2. Ensures that the path finishes at the designated goal landmark (row 1).
+        3. Prevents any arrivals at the start landmark or departures from the goal landmark (row 2).
 
         Args:
-            L (int): Number of landmarks.
+            prob (pl.LpProblem): The linear programming problem where constraints will be added.
+            x (pl.LpVariable): Decision variable representing travel between landmarks.
+            L (int): The total number of landmarks.
 
         Returns:
-            tuple[np.ndarray, list[int]]: Inequality constraint coefficients and the right-hand side of the inequality constraints.
+            None: This function modifies the `prob` object by adding three equality constraints in-place.
         """
         # Fill-in row 0.
         A_eq = np.zeros((3,L*L), dtype=np.int8)
@@ -211,27 +236,24 @@ class Optimizer:
         for i in range(3) :
             prob += (pl.lpSum([A_eq[i][j] * x[j] for j in range(L*L)]) == b_eq[i])
 
+
     def respect_order(self, prob: pl.LpProblem, x: pl.LpVariable, L: int):
         """
         Generate constraints to tie the optimization problem together and prevent 
         stacked ones, although this does not fully prevent circles.
-        -> Adds L-2 rows of constraints
+
+        This function adds constraints to the optimization problem that prevent 
+        simultaneous travel between landmarks in a way that would result in stacked ones.
+        However, it does not fully prevent circular paths.
 
         Args:
-            L (int): Number of landmarks.
+            prob (pl.LpProblem): The linear programming problem where constraints will be added.
+            x (pl.LpVariable): Decision variable representing travel between landmarks.
+            L (int): The total number of landmarks.
 
         Returns:
-            tuple[np.ndarray, list[int]]: Inequality constraint coefficients and the right-hand side of the inequality constraints.
+            None: This function modifies the `prob` object by adding L-2 equality constraints in-place.
         """
-        # A_eq = np.zeros(L*L, dtype=np.int8)
-        # ones = np.ones(L, dtype=np.int8)
-        # # Fill-in rows 4 to L+2
-        # for i in range(1, L-1) :           # Prevent stacked ones
-        #     for j in range(L) :
-        #         A_eq[i + j*L] = -1
-        #     A_eq[i*L:(i+1)*L] = ones
-        #     prob += (pl.lpSum([A_eq[j] * x[j] for j in range(L*L)]) == 0)
-
         # FIXME: weird 0 artifact in the coefficients popping up
         # Loop through rows 1 to L-2 to prevent stacked ones
         for i in range(1, L-1):
@@ -243,14 +265,19 @@ class Optimizer:
     def respect_user_must(self, prob: pl.LpProblem, x: pl.LpVariable, L: int, landmarks: list[Landmark]) :
         """
         Generate constraints to ensure that landmarks marked as 'must_do' are included in the optimization.
-        -> Adds a variable number of rows of constraints BUT CAN BE PRE COMPUTED
 
+        This function adds constraints to the optimization problem to ensure that landmarks marked as 
+        'must_do' are included in the solution. It precomputes the constraints and adds them to the 
+        problem accordingly.
 
         Args:
+            prob (pl.LpProblem): The linear programming problem where constraints will be added.
+            x (pl.LpVariable): Decision variable representing travel between landmarks.
+            L (int): The total number of landmarks.
             landmarks (list[Landmark]): List of landmarks, where some are marked as 'must_do'.
 
         Returns:
-            tuple[np.ndarray, list[int]]: Inequality constraint coefficients and the right-hand side of the inequality constraints.
+            None: This function modifies the `prob` object by adding equality constraints in-place.
         """
         ones = np.ones(L, dtype=np.int8)
         A_eq = np.zeros(L*L, dtype=np.int8)
@@ -264,52 +291,22 @@ class Optimizer:
                 prob += (pl.lpSum([A_eq[j] * x[j] for j in range(L*L)]) == 2)
 
 
-    # Prevent the use of a particular solution. TODO probably can be done faster just using resx
-    # def prevent_config(self, prob: pl.LpProblem, x: pl.LpVariable, resx):
-    #     """
-    #     Prevent the use of a particular solution by adding constraints to the optimization.
-
-    #     Args:
-    #         resx (list[float]): List of edge weights.
-
-    #     Returns:
-    #         tuple[list[int], list[int]]: A tuple containing a new row for A and new value for ub.
-    #     """
-
-    #     for i, elem in enumerate(resx):
-    #         resx[i] = round(elem)
-
-    #     N = len(resx)               # Number of edges
-    #     L = int(np.sqrt(N))         # Number of landmarks
-
-    #     nonzeroind = np.nonzero(resx)[0]                    # the return is a little funky so I use the [0]
-    #     nonzero_tup = np.unravel_index(nonzeroind, (L,L))
-
-    #     ind_a = nonzero_tup[0].tolist()
-    #     vertices_visited = ind_a
-    #     vertices_visited.remove(0)
-
-    #     ones = np.ones(L, dtype=np.int8)
-    #     h = np.zeros(L*L, dtype=np.int8)
-
-    #     for i in range(L) :
-    #         if i in vertices_visited :
-    #             h[i*L:i*L+L] = ones
-
-    #     return h, len(vertices_visited)-1
-
-
-    # Prevents the creation of the same circle (both directions)
     def prevent_circle(self, prob: pl.LpProblem, x: pl.LpVariable, circle_vertices: list, L: int) :
         """
-        Prevent circular paths by by adding constraints to the optimization.
+        Prevent circular paths by adding constraints to the optimization.
+
+        This function ensures that circular paths in both directions (i.e., forward and reverse) 
+        between landmarks are avoided in the optimization problem by adding the corresponding constraints.
 
         Args:
-            circle_vertices (list): List of vertices forming a circle.
+            prob (pl.LpProblem): The linear programming problem instance to which the constraints will be added.
-            L (int): Number of landmarks.
+            x (pl.LpVariable): Decision variable representing the travel between landmarks in the problem.
+            circle_vertices (list): List of indices representing the landmarks that form a circular path.
+            L (int): The total number of landmarks.
 
         Returns:
-            tuple[np.ndarray, list[int]]: A tuple containing a new row for constraint matrix and new value for upper bound vector.
+            None: This function modifies the `prob` object by adding two equality constraints that 
+                prevent circular paths in both directions for the specified circle vertices.
         """
         l = np.zeros((2, L*L), dtype=np.int8)
 
@@ -544,12 +541,8 @@ class Optimizer:
 
         return prob, x
 
-    def solve_optimization(
+
-            self,
+    def solve_optimization(self, max_time: int, landmarks: list[Landmark], max_landmarks: int = None) -> list[Landmark]:
-            max_time: int,
-            landmarks: list[Landmark],
-            max_landmarks: int = None
-        ) -> list[Landmark]:
         """
         Main optimization pipeline to solve the landmark visiting problem.
 
@@ -563,14 +556,12 @@ class Optimizer:
         Returns:
             list[Landmark]: The optimized tour of landmarks with updated travel times, or None if no valid solution is found.
         """
-        # 1. Setup the optimization proplem.
+        # Setup the optimization proplem.
         L = len(landmarks)
         prob, x = self.pre_processing(L, landmarks, max_time, max_landmarks)
 
-        # 2. Solve the problem
+        # Solve the problem and extract results.
         prob.solve(pl.PULP_CBC_CMD(msg=False, gapRel=0.1))
-
-        # 3. Extract Results
         status = pl.LpStatus[prob.status]
         solution = [pl.value(var) for var in x]  # The values of the decision variables (will be 0 or 1)
 
@@ -588,10 +579,6 @@ class Optimizer:
         timeout = 40
         while circles is not None :
             i += 1
-            # print(f"Iteration {i} of fixing circles")
-            # l, b = self.prevent_config(solution)
-            # prob += (pl.lpSum([l[j] * x[j] for j in range(L*L)]) == b)
-
             if i == timeout :
                 self.logger.error(f'Timeout: No solution found after {timeout} iterations.')
                 raise TimeoutError(f"Optimization took too long. No solution found after {timeout} iterations.")
@@ -611,7 +598,6 @@ class Optimizer:
             if circles is None :
                 break
 
-
         # Sort the landmarks in the order of the solution
         order = self.get_order(solution)
         tour =  [landmarks[i] for i in order]

backend/src/utils/refiner.py

@@ -4,7 +4,6 @@ from math import pi
 import yaml
 from shapely import buffer, LineString, Point, Polygon, MultiPoint, concave_hull
 
-
 from ..structs.landmark import Landmark
 from .get_time_distance import get_time
 from .take_most_important import take_most_important