feat: add randomSeed argument to COIN_CMD for reproducible CBC solves (#613)

pulp/apis/coin.py

@@ -99,6 +99,7 @@ def __init__(
         logPath=None,
         timeMode="elapsed",
         maxNodes=None,
+        randomSeed=None,
     ):
         """
         :param bool mip: if False, assume LP even if integer variables
@@ -117,6 +118,7 @@ def __init__(
         :param int strong: number of variables to look at in strong branching (range is 0 to 2147483647)
         :param str timeMode: "elapsed": count wall-time to timeLimit; "cpu": count cpu-time
         :param int maxNodes: max number of nodes during branching. Stops the solving when reached.
+        :param int randomSeed: random seed passed to CBC (``-randomSeed``) for reproducible results
         """
         if warmStart and not keepFiles and operating_system == "win":
             warnings.warn(
@@ -141,6 +143,7 @@ def __init__(
             logPath=logPath,
             timeMode=timeMode,
             maxNodes=maxNodes,
+            randomSeed=randomSeed,
         )
 
     def copy(self):
@@ -274,6 +277,7 @@ def getOptions(self):
             strong="strong {}",
             timeMode="timeMode {}",
             maxNodes="maxNodes {}",
+            randomSeed="randomSeed {}",
         )
 
         return [

pulp/tests/test_coin_cmd.py

@@ -220,6 +220,44 @@ def test_strong(self):
         )
         self.assertEqual("10", option_value)
 
+    def test_random_seed(self):
+        """
+        Test if setting randomSeed=20 adds randomSeed 20 to the command line.
+        """
+        # randomSeed is a public constructor argument that flows into optionsDict.
+        self.assertEqual(20, solvers.COIN_CMD(randomSeed=20).optionsDict["randomSeed"])
+        name = self._testMethodName
+        prob = LpProblem(name, const.LpMinimize)
+        x = prob.add_variable("x", 0, 4)
+        y = prob.add_variable("y", -1, 1)
+        z = prob.add_variable("z", 0)
+        w = prob.add_variable("w", 0)
+        prob += x + 4 * y + 9 * z, "obj"
+        prob += x + y <= 5, "c1"
+        prob += x + z >= 10, "c2"
+        prob += -y + z == 7, "c3"
+        prob += w >= 0, "c4"
+        logFilename = name + ".log"
+        self.solver.optionsDict["logPath"] = logFilename
+        self.solver.optionsDict["randomSeed"] = 20
+        pulpTestCheck(
+            prob,
+            self.solver,
+            [const.LpStatusOptimal],
+            {x: 4, y: -1, z: 6, w: 0},
+        )
+        if not os.path.exists(logFilename):
+            raise PulpError(f"Test failed for solver: {self.solver}")
+        if not os.path.getsize(logFilename):
+            raise PulpError(f"Test failed for solver: {self.solver}")
+        command_line = COIN_CMD_CBCOptionsTest.read_command_line_from_log_file(
+            logFilename
+        )
+        option_value = COIN_CMD_CBCOptionsTest.extract_option_from_command_line(
+            command_line, option="randomSeed", grp_pattern="\\d+"
+        )
+        self.assertEqual("20", option_value)
+
 
 class COIN_CMDTest(BaseSolverTest.PuLPTest):
     solveInst = solvers.COIN_CMD