new example: pell equation

Author: lperron

examples/python/BUILD.bazel

@@ -58,6 +58,8 @@ code_sample_py("maze_escape_sat")
 
 code_sample_py("no_wait_baking_scheduling_sat")
 
+code_sample_py("pell_equation_sat")
+
 code_sample_py("pentominoes_sat")
 
 code_sample_py("prize_collecting_tsp_sat")
@@ -96,6 +98,8 @@ code_sample_py("task_allocation_sat")
 
 code_sample_py("tasks_and_workers_assignment_sat")
 
+code_sample_py("test_scheduling_sat")
+
 code_sample_py("tsp_sat")
 
 code_sample_py("vendor_scheduling_sat")

examples/python/golomb8.py

@@ -23,11 +23,8 @@
 """
 
 from absl import app
-from absl import flags
 from ortools.constraint_solver import pywrapcp
 
-FLAGS = flags.FLAGS
-
 # We disable the following warning because it is a false positive on constraints
 # like: solver.Add(x == 0)
 # pylint: disable=g-explicit-bool-comparison

examples/python/line_balancing_sat.py

@@ -47,7 +47,7 @@
 )
 
 
-class SectionInfo(object):
+class SectionInfo:
     """Store model information for each section of the input file."""
 
     def __init__(self):

examples/python/no_wait_baking_scheduling_sat.py

@@ -50,7 +50,7 @@
 DISPLAY = "display"
 
 
-class Task(object):
+class Task:
     """A unit baking task.
 
     - Simple baking tasks have a fixed duration. They are performed by workers.
@@ -64,7 +64,7 @@ def __init__(self, name, min_duration, max_duration):
         self.max_duration = max_duration
 
 
-class Skill(object):
+class Skill:
     """The skill of a worker or the capability of a machine."""
 
     def __init__(self, name, efficiency):
@@ -73,7 +73,7 @@ def __init__(self, name, efficiency):
         self.efficiency = efficiency
 
 
-class Recipe(object):
+class Recipe:
     """A recipe is a sequence of cooking tasks."""
 
     def __init__(self, name):
@@ -85,7 +85,7 @@ def add_task(self, resource_name, min_duration, max_duration):
         return self
 
 
-class Resource(object):
+class Resource:
     """A resource is a worker, a machine, or just some space for cakes to rest.
 
     - Workers have a capacity of 1 and can have variable efficiency.
@@ -106,7 +106,7 @@ def add_skill(self, skill_name, efficiency):
         return self
 
 
-class Order(object):
+class Order:
     """An order is a recipe that should be delivered at a given due date."""
 
     def __init__(self, unique_id, recipe_name, due_date, quantity):

examples/python/pentominoes_sat.py

@@ -20,6 +20,9 @@
 
 This problem comes from the game Katamino:
 http://boardgamegeek.com/boardgame/6931/katamino
+
+This example also includes suggestions from
+https://web.ma.utexas.edu/users/smmg/archive/1997/radin.html
 """
 
 from collections.abc import Sequence
@@ -42,6 +45,8 @@
     "pieces", "FILNPTUVWXYZ", "The subset of pieces to consider."
 )
 
+_HEIGHT = flags.DEFINE_integer("height", 5, "The height of the box.")
+
 
 def is_one(mask: List[List[int]], x: int, y: int, orientation: int) -> bool:
     """Returns true if the oriented piece is 1 at position [i][j].
@@ -104,8 +109,9 @@ def orientation_is_redundant(mask: List[List[int]], orientation: int) -> bool:
 
 def generate_and_solve_problem(pieces: Dict[str, List[List[int]]]) -> None:
     """Solves the pentominoes problem."""
-    box_width = len(pieces)
-    box_height = 5
+    box_height = _HEIGHT.value
+    box_width = 5 * len(pieces) // box_height
+    print(f"Box has dimension {box_height} * {box_width}")
 
     model = cp_model.CpModel()
     position_to_variables: List[List[List[cp_model.IntVar]]] = [
@@ -142,8 +148,8 @@ def generate_and_solve_problem(pieces: Dict[str, List[List[int]]]) -> None:
     status = solver.solve(model)
 
     print(
-        f"Problem {_PIECES.value} solved in {solver.wall_time}s with status"
-        f" {solver.status_name(status)}"
+        f"Problem {_PIECES.value} box {box_height}*{box_width} solved in"
+        f" {solver.wall_time}s with status {solver.status_name(status)}"
     )
 
     # Print the solution.
@@ -183,6 +189,16 @@ def main(argv: Sequence[str]) -> None:
             print(f"Piece {p} not found in the list of pieces")
             return
         selected_pieces[p] = pieces[p]
+    if (len(selected_pieces) * 5) % _HEIGHT.value != 0:
+        print(
+            f"The height {_HEIGHT.value} does not divide the total area"
+            f" {5 * len(selected_pieces)}"
+        )
+        return
+    if _HEIGHT.value < 3 or 5 * len(selected_pieces) // _HEIGHT.value < 3:
+        print(f"The height {_HEIGHT.value} is not compatible with the pieces.")
+        return
+
     generate_and_solve_problem(selected_pieces)
 
 

examples/python/single_machine_scheduling_with_setup_release_due_dates_sat.py

@@ -27,7 +27,7 @@
 )
 _PARAMS = flags.DEFINE_string(
     "params",
-    "num_search_workers:16,log_search_progress:false,max_time_in_seconds:45",
+    "num_search_workers:16,log_search_progress:true,max_time_in_seconds:45",
     "Sat solver parameters.",
 )
 _PREPROCESS = flags.DEFINE_bool(