docplex (a.k.a. IBM® Decision Optimization CPLEX® Modeling for Python) is a Python modeling API that provides modules for mathematical programming via CPLEX and constraint programming via CP Optimizer.
Questions tagged [docplex]
316 questions
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docplex "Error: Model has non-convex objective:"
I would like to solve a mix-integer nonlinear programming problem in phyton. I use the codes you see in below. I'm taking this error:
Error: Model has non-convex objective: x_1_2 * distanceofclusters_1_2 + ...
How can I fix this? My model is using…
Ebru Pekel
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Handling variables in the denominator of an objective function in CPLEX Python
I wish to solve a linear program with an objective function:
Here x[i][j] are decision variables and y[i][j] are already precomputed.
I was writing the code for this in CPLEX python (DOcplex) and was receiving the error that the denominator can…
flux
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How to model a scheduling problem with interruptible tasks using docplex.cp (Constraint programming)?
I would like to model a scheduling problem using constraint programming (Python API of CPLEX : docplex.cp) where I have machines to allocate to activities. Activities are performed during work shifts and some tasks can be divised in at most 3 parts…
Jérémy André
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Computation Speed differs between OPL and Docplex
I've got a problem at solving an MIP with Docplex. The computation speed for my problem differs between 35 and 120 seconds while it is solved within 5 seconds using the OPL version. The model formulation does not differ between Python and OPL.
Does…
memphisDepay21
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Docplex: Keyerror where there wasn't one before
I am trying to run a replication study, and I have run the code in question multiple times without error. I took a little time off to work on some other projects, and it suddenly doesn't work, I have run into the following error (with different key…
Sean
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How we can use a decision variable as an index of another decision variable using ILOG CP optimizer in python?
I am modeling a vehicle routing and scheduling problem using CP. I have 2 kinds of decision variables, that is, sequencing and start time of each node.
The sequencing variable contains the node number, and start time of each node depends on the…
Saeede Hosseini
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Dynamic worker constraint in CPLEX python
I've been working at a rcpsp problem using docplex in python.
I consider 10 tasks with indicative costs and a worker that has to complete these tasks in 10 timeframes (can be weeks, days etc.).
One of my constraints is that the worker can perform a…
Dru_np
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AttributeError: 'NoneType' object has no attribute 'get_values'
I am new in coding and need your help.
I get the following error:
line 159, in _get_solution
xs = np.array(ms.get_values(self.int_var)).reshape(self.path_n, self.orderbook_n)
AttributeError: 'NoneType' object has no attribute 'get_values'
after…
Bsarv
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Dual infeasible due to empty column 'x1' in Python w/Cplex/Docplex
I would really appreciate any input for this optimization problem:
I am failing to assign my variables the values 1,2,3,4,5 for i and j, I think that is why I am getting this error:
Dual infeasible due to empty column x1.
Am I on the right…
jopro
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ConflictRefiner() returns a different upper bound than the one saved in the model
My model status is integer infeasible. I used ConflictRefiner() to check which constraints are mutually contradictory.
Then I use display_conflicts to check which constraints are "at fault".
This is the output:
I found this weird since my ub is set…
DP_
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Is there a docplex function for getting solution of more than one variables for using in lazy cut?
I code an optimization problem in python (docplex) base on here but my cut is something like that sum(X) <= N + M*sum(Y, Z), X, Y and Z are decision vars. I do not know how I can pass the solution of X, Y, Z to self.get_cpx_unsatisfied_cts([ct],…
moh jor
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How to add a time-window in vehicle routing problem?
I am studying a project in Python. It's a vehicle routing problem with time-window. In this study, depot is denoted by 1. And there are 14 customers which are fulfilled with 4 vehicles. Each vehicle has 50 tons capacity. Travel time between every…
ayca
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CVRP model formulation
I am trying to solve CVRP problem using binary variables. Xr,i,j is the decision variable.
Below is the way I have created the decission variable using docplex.
na_travel = mymodel.binary_var_cube(vehicle, nodes, nodes, name='X');
We can take that…
suresh_chinthy
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How to change Cplex model during solution generation?
I have a Cplex model with several constraints and a solution pool. One of my constraint is :
R_alt=[i for i in R if i not in SetAlt]
model.add_constraints((model.sum(x[i, j] for j in R2 ) == 2 for i in R_alt),"6C" )
…
Ashkan Rezaee
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Getting unique solutions with python cplex solution pool
I have an MILP model that I try to solve with cplex python API. I need to get more than one solution. The problem is that when I get for example 50 solutions from my cplex pool, these solutions are very much similar. How can I somehow shuffle before…
Sana.Nz
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