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1500 questions
6
votes
1 answer
Optimal Energy Charging/discharging Scheduling Problem
I'm new to IBM CP optimizer.
I want to make charging / discharging scheduling based on cost (value will change on time) and my objective function…
JG.K
- 61
- 1
6
votes
0 answers
Semi-definite Programming, non standard notation
The usual way to define a semi-definite program (SDP), e.g., as given in Boyd and Vandenberghe's convex optimization book, is:
$$
\begin{array}{cl}
\min & c^\top x \\
\mathrm{s.t.} & 0 \succeq x_1 F_1+ \ldots+x_nF_n + G \\
& Ax =…
independentvariable
- 3,980
- 10
- 36
6
votes
1 answer
assigning values to IntVar if and only if BoolVar, else zero [or-tools]
If I have an IntVar s[j] stored in a vector s, is it possible to iterate for (a period of time) t and create a BoolVar b such that b[t] is true if and only if s[j]==t? I tried setting some restrictions:
for (int j = 0; j < nbTasks; ++j)
{
…
Diego R. Troncoso
- 635
- 4
- 13
6
votes
0 answers
OptionalIntervalVar enforced but not working OR-TOOLS
I'm using OptionalIntervalVar and then maximizing the starts. The optimal solution is not affecting the other variables that creates the OptionalIntervalVar (i mean the constraint starts[j]+sizes[j]==ends[j]), so I suppose that there are not…
Diego R. Troncoso
- 635
- 4
- 13
6
votes
2 answers
Optimising the current model
After developing the MIP model I noticed that solver is taking a lot of time to reach the solution. So, how should I approach to optimize the current model?
Are there any visualization tools or any tools that are helpful in optimizing the model.
ooo
- 1,589
- 4
- 12
6
votes
0 answers
Benefits of removing slack variables during presolve
I was reading Tobias Achterberg's thesis, and on page 138 he mentions the following presolving technique for linear equations (I'm slightly paraphrasing Example 10.2):
Consider the equation $4x_1+7x_2+3x_3+s=20$ with $s\geq0$, and assume that $s$…
Nikos Kazazakis
- 12,121
- 17
- 59
6
votes
0 answers
Can demand be modeled by a limited amount of probability distributions?
In stochastic inventory control, it is very important to model the demand appropriate to set e.g. order levels. Demand can be fit to a certain probability distribution via many means (e.g. a goodness of fit test). However, following common…
Steven01123581321
- 1,043
- 6
- 12
6
votes
1 answer
How to propagate time using linear inequalities?
I have an adjacency matrix $G_{i,j}$ that tells the distance between $i$ to $j$ (between 0 to 1) if there is no edge between $i$ to $j$ I am putting a large integer $100$.
This is my previous question related to it.
I am trying to linearize the…
ooo
- 1,589
- 4
- 12
6
votes
1 answer
How to write a constraint for a directed graph?
I'm working on an optimization problem regarding a directed acyclic graph. The constraint looks in pyomo like this:
model.K = RangeSet(0,n_edges)
model.con_part=ConstraintList()
for k in model.K:
…
teshim
- 61
- 1
6
votes
2 answers
Assignment problem where assignments must be done sequentially
I have a weird planning problem. I think it falls under the assignment category, but I'm not sure because I'm not familiar with assignment problems, and also because there is a "temporal" angle to it, which maybe makes it a bit different from…
DeltaIV
- 255
- 1
- 6
6
votes
0 answers
Modelling issue with precedence constraint in OR-Tools
I'm trying to solve an RCPSPDc model It is infeasible, although Ilog Cplex solves it, so I think I have a modelling issue. I have more constraints but the precedence is the one that makes it infeasible.
//Inicializar Modelo
CpModelBuilder…
Diego R. Troncoso
- 635
- 4
- 13
6
votes
1 answer
Linearizing objective function with absolute differences
I want to turn this objective function
$$\max \sum_{i=1}^{N-1} \sum_{j=i+1}^N |TX_i^T - TX_j^T|$$
where $T$ is just a vector with increasing integers (e.g $[1 \ 2]$) and $X_i$ is a vector with $n$ variables like $[x_{11} \ x_{12}]$.
Is there…
T K.
- 61
- 1
6
votes
1 answer
Gurobi stuck at start - 16GB RAM exhausted
I'm solving a large instance using Gurobi 7.0, 64-bit version on machine with 16GB of RAM. Gurobi is stuck at the start and all the memory is exhausted. Here is the output:
5378534 variables, all binary
16140318 constraints, all linear; 319218593…
lazar
- 73
- 3
6
votes
0 answers
Data Formulation for Mixed-Integer-Programming Models
Until now, I have used the Gurobi, CPLEX and OR-Tools (GCO) interface to formulate mixed-integer-programming models.
Recently, I have discovered MiniZinc and want to utilize it to formulate big models.
With GCO I would only initialize the decision…
Georgios
- 1,193
- 5
- 21
6
votes
0 answers
Demonstrating a given solution is basic for a MCFP?
Given a minimum-cost flow problem, how could I go about demonstrating that a specific solution (as sets of basic and non-basic (!) arcs that build a rooted spanning tree for a given graph) is basic and feasible for the problem?
Update: the MCF…
Johnny Bueti
- 253
- 2
- 5