我正在尝试使用 IBM 的 CPLEX Python API 解决线性规划问题。它涉及两组等式约束。当我们使用两组约束中的任何一组时,下面的代码工作正常,但在使用两组约束时无法找到解决方案。约束条件是: 第一个约束条件: Wx' = c', where W = [[20,0,0],[0,20,30]], x = [a,b,c],c=[20,30] 第二个约束条件:Vx' = e', where V = [[1,1,0],[0,0,1]], x = [a,b,c],c=[1,1]目标函数: minimize a + c满足两组约束的一种解决方案是a=1, b=0, c=1。我在 Cplex Python 中引入两组约束的方式存在错误。我的代码如下。要检查代码本身是否适用于任一组约束,请注释掉一组约束。import cplexfrom cplex.exceptions import CplexErrorimport sysdef populatebynonzero(prob): my_obj = [1.0, 0.0, 1.0] my_ub = [1.0] * len(my_obj) my_lb = [0.0] * len(my_obj) my_colnames = ["a", "b", "c"] prob.objective.set_sense(prob.objective.sense.minimize) prob.variables.add(obj = my_obj, ub = my_ub, lb = my_lb ,names = my_colnames) # first set of equality constraints: Wx' = c', where W = [[20,0,0],[0,20,30]], x = [a,b,c], c=[20,30] my_rhs = [20.0, 30.0] my_rownames = ["c1", "c2"] my_sense = "E" * len(my_rownames) rows = [0,1,1] cols = [0,1,2] vals = [20.0,20.0,30.0] prob.linear_constraints.add(rhs = my_rhs, senses = my_sense,names = my_rownames) prob.linear_constraints.set_coefficients(zip(rows, cols, vals)) # second set of equality constraints: Vx' = e', where V = [[1,1,0],[0,0,1]], x = [a,b,c], c=[1,1] my_rhs = [1.0, 1.0] my_rownames = ["e1", "e2"] my_sense = "E" * len(my_rownames) rows = [0,0,1] cols = [0,1,2] vals = [1.0,1.0,1.0] prob.linear_constraints.add(rhs = my_rhs, senses = my_sense,names = my_rownames) prob.linear_constraints.set_coefficients(zip(rows, cols, vals))def lpex1(): try: my_prob = cplex.Cplex() handle = populatebynonzero(my_prob) my_prob.solve() except CplexError, exc: print exc return numrows = my_prob.linear_constraints.get_num() numcols = my_prob.variables.get_num()
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