After creating a model and solving the LP with some specialized cuts, I want to solve the IP version of the problem but changing the type of certain variables. In JAVA this uses the function:
IloConversion conversion(IloNumVar var, IloNumVarType type) throws IloException
What is the equivalent in DOCPLEX?
The corresponding API in DOcplex is not documented yet, as it is not well tested enough. This said, you can try
myvar.set_vartype('I')
To switch a variable to integer type (or 'B') for binary. This code is provided as-is for now. Le us know if this works for you. This method accepts either variable type instances (e.g. model.binary_vartype) or one-letter string ('B', 'I', 'C', 'S' for semi continuous, 'N" for semi-integer)
In this sample, I maximize the sum of four binaries , whose sum is less than 3.5.
When I change their type to continuous, one of them is set to 0.5 and the objective is equal to 3.5
code:
def test_vartype():
m = Model()
m.environment.print_information()
bs = m.binary_var_list(4, name='b')
sumbs = m.sum(bs)
m.add(sumbs <= 3.5)
m.maximize(m.sum(bs))
s1 = m.solve()
assert s1
s1.display()
# now switch
for b in bs:
b.set_vartype(m.continuous_vartype)
# m.print_information()
s2 = m.solve(log_output=False)
m.report()
s2.display()
and the output is:
* Python version 3.7.7, located at: C:\python\anaconda2020.02\envs\docplex_dev37\python.exe
* docplex is present, version is 2.19.0
* CPLEX library is present, version is 20.1.0.0, located at: C:\OPTIM\cplex_distrib\cplex2001R1\python\3.7\x64_win64
* pandas is present, version is 1.0.3
* numpy is present, version is 1.18.1
solution for: docplex_model1
objective: 3
b_0 = 1
b_1 = 1
b_2 = 1
* model docplex_model1 solved with objective = 3.500
solution for: docplex_model1
objective: 3.500
b_0 = 1.000
b_1 = 1.000
b_2 = 1.000
b_3 = 0.500