Proper way to use opl.set_input() of doopl for parameters (not tuple)

Question

I'm trying to run the CPLEX .mod file within Python. An instructor on how to do this exists in the following link:

How to run a .mod file (CPLEX) using python?

But it seems that (maybe) only the tuple is sent from Python into CPLEX. In my case, there is a loop in the CPLEX .mod file like the following:

for (var i = lowerBound; i <= upperBound; i++) {
...
} 

I want to send parameters lowerBound and upperBound from Python to CPLEX .mod file. For this aim, I define a variable inside the CPLEX .mod file, before the for loop, as follows:

var lowerBound = ...;
var upperBound = ...;

Then, I use the following command in Python:

from doopl.factory import *
with create_opl_model(model="model.mod") as opl:
    opl.set_input("upperBound", 50)
    opl.set_input("lowerBound", 1)
    opl.run()

but the following error comes out:

ERROR at 17:18 model.mod: Scripting parser error: missing expression.

I would like to say that in the CPLEX .mod lines 17 and 18 are:

var lowerBound = ...; 
var upperBound = ...;

Question: I wonder if only tuples are sent with opl.set_input ()? To understand this, I did something like the followings:

Inside CPLEX .mod:

tuple bounds {
        int lowerBound;
        int upperBound;
        
    }

    
for (var i = lowerBound; i <= upperBound; i++) {
    ...
}

Inside Python:

from doopl.factory import *

Bounds = [
    (1, 50),
    ]

with create_opl_model(model=" model.mod") as opl:
    opl.set_input("bounds", Bounds)
    opl.run()

But this time, there is an error like the following:

ERROR at 20:7 model.mod: Scripting parser error: missing ';' or newline between statements.

I would like to say that in the CPLEX .mod file line 20 is related to the definition of tuple bounds, which is:

tuple bounds {
        int lowerBound;
        int upperBound;
        
    }

What could be the solution to this?

Answer 1

you need to use tuple sets but in

tuple bounds {
        int lowerBound;
        int upperBound;
        
    }

that s not what you do.

You should write

tuple typebounds {
        int lowerBound;
        int upperBound;
        
    }

{typebounds} bounds=...;

in your .mod file

Let me share a full example:

from doopl.factory import *
# Data

Buses=[
        (40,500),
        (30,400)
        ]

MinAndMax=[(1,5)]

# Create an OPL model from a .mod file
with create_opl_model(model="zootuplesetwithminandmax.mod") as opl:
    # tuple can be a list of tuples, a pandas dataframe...
    opl.set_input("buses", Buses)
    opl.set_input("singletonMinAndMax", MinAndMax)

    # Generate the problem and solve it.
    opl.run()

    # Get the names of post processing tables
    print("Table names are: "+ str(opl.output_table_names))

    # Get all the post processing tables as dataframes.
    for name, table in iteritems(opl.report):
        print("Table : " + name)
    for t in table.itertuples(index=False):
            print(t)

    # nicer display
    for t in table.itertuples(index=False):
        print(t[0]," buses ",t[1], "seats")

with zootuplesetwithminandmax.mod

int nbKids=300;

// a tuple is like a struct in C, a class in C++ or a record in Pascal
tuple bus
{
key int nbSeats;
float cost;
}

// This is a tuple set
{bus} buses=...;

tuple minandmax
{
int m;
int M;
}

{minandmax} singletonMinAndMax=...;

int minBuses=first(singletonMinAndMax).m;
int maxBuses=first(singletonMinAndMax).M;


// asserts help make sure data is fine
assert forall(b in buses) b.nbSeats>0;
assert forall(b in buses) b.cost>0;

// decision variable array
dvar int+ nbBus[buses] in minBuses..maxBuses;

// objective
minimize
 sum(b in buses) b.cost*nbBus[b];
 
// constraints
subject to
{
 sum(b in buses) b.nbSeats*nbBus[b]>=nbKids;
}

tuple solution
{
  int nbBus;
  int sizeBus;
}

{solution} solutions={<nbBus[b],b.nbSeats> | b in buses};