René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Segmentation fault when running LPs repeatedly","articleBody":"Hello I am using a MAC OS Big Sur Version 11.3.1 \r\n\r\nWhen I run the solver multiple times SOMETIMES it segmentation faults, I dont know if this is because of qsopt_ex or because of the cython library. Just copy the code below into a file called `reproducing_seg_fault.py` and run the program like 20 or so times consecutively. One of the times will result in a segfault (see here) \r\n\u003cimg width=\"738\" alt=\"Screen Shot 2023-03-24 at 8 20 21 PM\" src=\"https://user-images.githubusercontent.com/5061556/227667055-e091b53e-aa03-4197-a068-489729020300.png\"\u003e\r\n\r\nCode here:\r\n\r\n```\r\nimport qsoptex\r\n\r\nimport faulthandler\r\nfaulthandler.enable()\r\n\r\n#import logging\r\n#logging.basicConfig(level=logging.NOTSET)\r\n\r\nclass Polytope:\r\n    def __init__(self, A, b):\r\n        self.A = A\r\n        self.b = b\r\n        self.status = None\r\n        \"\"\"\r\n            The status variable carries the status of a most recent solve, if it is set to None then an LP run has not occurred yet \r\n        \"\"\"\r\n        self.p = None\r\n\r\n    def dimension(self):\r\n        return len(self.A[0])\r\n    \r\n    def inequality_count(self):\r\n        return len(self.A)\r\n\r\n    #given an objective array c we attempt to maximize it and return the status, surprising the \"c\" tells us what the dimension of the problem is \r\n    def maximize(self, c, flag_integers=True): \r\n        self.p = qsoptex.ExactProblem()\r\n        for var_number in range(len(c)):\r\n            self.p.add_variable(name='x' + str(var_number), \r\n                objective=c[var_number], \r\n                lower=0, upper=1)\r\n\r\n        for constraint_number in range(self.inequality_count()):\r\n            self.p.add_linear_constraint(qsoptex.ConstraintSense.LESS, \r\n                dict(('x' + str(var_number), self.A[constraint_number][var_number]) for var_number in range(len(c))), \r\n                rhs = self.b[constraint_number], \r\n                name='c' + str(constraint_number))\r\n\r\n        self.p.set_objective_sense(qsoptex.ObjectiveSense.MAXIMIZE)\r\n        self.p.set_param(qsoptex.Parameter.SIMPLEX_DISPLAY, 1)\r\n        print(\"before seg fault: \")\r\n        self.status = self.p.solve()\r\n        print(\"after seg fault: \")\r\n\r\n\r\n    \r\n\r\nif __name__ == '__main__':\r\n\r\n    #running one at a time never results in a segfault\r\n    #running both of these repeatedly results in a segfault \r\n\r\n \r\n    A_matrix =  [[1037066, 2074132, 1648264, 796528, 1593056, 686112, 1372224, 244448, 488896, 977792, 1955584, 1411168, 322336, 644672, 1289344, 78688, 157376, 314752, 629504, 1259008], [-1037066, -2074132, -1648264, -796528, -1593056, -686112, -1372224, -244448, -488896, -977792, -1955584, -1411168, -322336, -644672, -1289344, -78688, -157376, -314752, -629504, -1259008]]\r\n    b_matrix =  [2463098, -2463098]\r\n    c_matrix =  [0, -1, 1, -1, 1, -1, 0, 0, 0, 0, -1, 0, -1, -1, 0, 1, 0, 1, 1, -1]\r\n\r\n    test_polyhedron = Polytope(A_matrix, b_matrix)\r\n    \r\n    test_polyhedron.maximize( c_matrix)\r\n\r\n    A_matrix =  [[1037066, 2074132, 1648264, 796528, 1593056, 686112, 1372224, 244448, 488896, 977792, 1955584, 1411168, 322336, 644672, 1289344, 78688, 157376, 314752, 629504, 1259008], [-1037066, -2074132, -1648264, -796528, -1593056, -686112, -1372224, -244448, -488896, -977792, -1955584, -1411168, -322336, -644672, -1289344, -78688, -157376, -314752, -629504, -1259008]]\r\n    b_matrix =  [2463098, -2463098]\r\n    c_matrix =  [0, -1, 1, -1, 1, -1, 0, 0, 0, 0, -1, 0, -1, -1, 0, 1, 0, 1, 1, -1]\r\n\r\n    test_polyhedron = Polytope(A_matrix, b_matrix)\r\n\r\n    test_polyhedron.maximize( c_matrix)\r\n```","author":{"url":"https://github.com/frogeyedpeas","@type":"Person","name":"frogeyedpeas"},"datePublished":"2023-03-25T00:21:00.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/8/python-qsoptex/issues/8"}