Google OR-Tools 库：类型错误 GetOrMakeIndex

Question

我正在研究 google OR-Tools 库，我遇到了这个我无法理解的问题。首先，如果我将 nqueens 示例中的代码复制并粘贴到 official guide.

中，我会得到同样的错误

我以经典的 n 皇后问题为例：

def main(board_size):

   #1) Declare CP-SAT model
   model = cp_model.CpModel()

   #2) Create the variables
   # queens[j]=i --> j = colonna, i (valore) = riga
   queens = [model.NewIntVar(0, board_size - 1, "queens%i" %i) for i in range(board_size)]

   #3) Constraints
   # Row constraint
   model.AddAllDifferent(queens)

   # Diagonal constraint
   model.AddAllDifferent([queens[j] - j for j in range(board_size)])
   model.AddAllDifferent([queens[j] + j for j in range(board_size)])

   #4) Call the solver and display the results
   solver = cp_model.CpSolver()
   solution_printer = NQueenSolutionPrinter(queens)
   solver.parameters.enumerate_all_solutions = True
   solver.Solve(model, solution_printer)

if __name__ == '__main__':
   size = 4
   if len(sys.argv) > 1:
      size = int(sys.argv[1])
   main(size)

控制台给我这个错误：

Traceback (most recent call last):

File "C:\Users\W\.spyder-py3\temp.py", line 90, in <module>
  main(size)

File "C:\Users\W\.spyder-py3\temp.py", line 67, in main
  model.AddAllDifferent([queens[j] - j for j in range(board_size)])

File "C:\ProgramData\Anaconda3\lib\site-packages\ortools\sat\python\cp_model.py", line 926, in AddAllDifferent
  [self.GetOrMakeIndex(x) for x in variables])

File "C:\ProgramData\Anaconda3\lib\site-packages\ortools\sat\python\cp_model.py", line 926, in <listcomp>
  [self.GetOrMakeIndex(x) for x in variables])

File "C:\ProgramData\Anaconda3\lib\site-packages\ortools\sat\python\cp_model.py", line 1583, in GetOrMakeIndex
  raise TypeError('NotSupported: model.GetOrMakeIndex(' + str(arg) +

TypeError: NotSupported: model.GetOrMakeIndex((queens0))

因此，查看 GetOrMakeIndex 方法的定义：

def GetOrMakeIndex(self, arg):
    """Returns the index of a variable, its negation, or a number."""
    if isinstance(arg, IntVar):
        return arg.Index()
    elif (isinstance(arg, _ProductCst) and
          isinstance(arg.Expression(), IntVar) and arg.Coefficient() == -1):
        return -arg.Expression().Index() - 1
    elif isinstance(arg, numbers.Integral):
        cp_model_helper.AssertIsInt64(arg)
        return self.GetOrMakeIndexFromConstant(arg)
    else:
        raise TypeError('NotSupported: model.GetOrMakeIndex(' + str(arg) +

我想到变量无法识别它作为参数接收的变量类型。知道如何解决这个问题吗？

Answer 1

这需要最新版本的库。你用的是哪一个？

Google OR-Tools 库：类型错误 GetOrMakeIndex

Google OR-Tools library: Type Error GetOrMakeIndex

or-tools

cp-sat-solver