Pulp with Real Numbers in Python

[Shansal]

Hi,

I use pulp module to solve my some optimization problems. With integer numbers, it works like a charm. I wonder if it is possible for pulp to work with real numbers.

Here is a sample optimization problem I build for my project.

prob = pulp.LpProblem("example", pulp.LpMinimize)

    # Variable represent number of times device i is used
    n1 = pulp.LpVariable("n1", 1, 5, pulp.LpInteger)
    n2 = pulp.LpVariable("n2", 0, max_exp, pulp.LpInteger)
    n3 = pulp.LpVariable("n3", 0, max_exp, pulp.LpInteger)
    n4 = pulp.LpVariable("n4", 0, max_exp, pulp.LpInteger)
    n5 = pulp.LpVariable("n5", 0, max_exp, pulp.LpInteger)


    # The objective function that we want to minimize: the total cost
    prob += n1 * Device1[-1] + n2 * Device2[-1] + n3 * Device3[-1] + n4 * Device4[-1] + n5 * Device5[-1], "Minimize total cost"

    # Constraint that we use no more than max. devices per controller device
    prob += n2 + n3 + n4 + n5 <= n1*max_exp

    #Constraint (total_UI >= (target_AI + target_BI))
    prob += n1 * Device1[0] + n2 * Device2[0] + n3 * Device3[0] + n4 * Device4[0] + n5 * Device5[0] >= (Target[0]+Target[2])

    #Constraint ((total_UO + total_BO) >= target_BO)
    prob += n1 * Device1[1] + n2 * Device2[1] + n3 * Device3[1] + n4 * Device4[1] + n5 * Device5[1] + n1 * Device1[3] + n2 * Device2[3] + n3 * Device3[3] + n4 * Device4[3] + n5 * Device5[3]>= (Target[3])

    #Constraint [total_UO + total_AO + total_BO - target_BO] >= target_AO
    prob += n1 * Device1[1] + n2 * Device2[1] + n3 * Device3[1] + n4 * Device4[1] + n5 * Device5[1] + n1 * Device1[2] + n2 * Device2[2] + n3 * Device3[2] + n4 * Device4[2] + n5 * Device5[2] + n1 * Device1[3] + n2 * Device2[3] + n3 * Device3[3] + n4 * Device4[3] + n5 * Device5[3] >= (Target[1]+Target[3])        
    
    # Actually solve the problem, this calls GLPK so you need it installed
    prob.solve()

Lets assume DeviceX[-1] be a real number. Could you make the required changes?

Thanks in advance.

[TrustyTony]

If you would multiply all values by constant, say 1000000, and divide solution accordingly, maybe it could work out to transform the problem to integer realm.

[Gribouillis]

If you would multiply all values by constant, say 1000000, and divide solution accordingly, maybe it could work out to transform the problem to integer realm.

This is not a good idea. LP problems are much easier to solve with real numbers than with integers, so yes I think pulp can work with real numbers, but since I don't use pulp, I can't make the required changes to your code. The solution is in the pulp documentation https://www.coin-or.org/PuLP/ .