# \[JuMP\] Speeding up constraint violation inspection
**URL:** https://discourse.julialang.org/t/jump-speeding-up-constraint-violation-inspection/111303
**Category:** Optimization (Mathematical)
**Tags:** jump
**Created:** [March 7, 2024, 2:50pm UTC](https://discourse.julialang.org/t/jump-speeding-up-constraint-violation-inspection/111303 "2024-03-07T14:50:53Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@HenriDeh](https://discourse.julialang.org/u/HenriDeh)
#### Post date: [March 7, 2024, 2:50pm UTC](https://discourse.julialang.org/t/jump-speeding-up-constraint-violation-inspection/111303/1 "2024-03-07T14:50:53Z")
Hello,
I’m trying to make an oracle that checks for constraint violations in a solved model (ie. constraints that were not initially in the model) and add some of them to the model to then reoptimize. The inspector looks like this:
```julia
function inspector(model, TAXA)
τ = model[:τ]
x = model[:x]
triples = Dict{Int, NTuple{3,Int}}()
for q in TAXA
worst = 0
for (i,j,p) in combinations(TAXA,3)
q ∉ (i,j,p) || continue
violation = value(2(τ[i,j]+τ[j,q]+τ[p,q]) - τ[i,j] - τ[i,p] - τ[j,p] - (8 + 6*sum(x[q,v,2] for v in TAXA if v∉(i,j,p,q))))
if violation < worst
worst = violation
triples[q] = (i,j,p)
end
end
end
```
TAXA is just a set used in the model. x and tau are variables (actually they are expressions that substitute underlying variables/sum of variables, for a clearer syntax).
This is a O(n^4) oracle that generate O(n) cuts, quite slow, but I find that adding all the constraints is faster than executing the above code so I believe I’m doing something inefficient here. Plus I’m getting the
`Warning: The addition operator has been used on JuMP expressions a large number of times. This warning is safe to ignore but may indicate that model generation is slower than necessary. For performance reasons, you should not add expressions in a loop. Instead of x += y, use add_to_expression!(x,y) to modify x in place. If y is a single variable, you may also use add_to_expression!(x, coef, y) for x += coef*y.`
I think the slow part is when I’m computing the violation for a quadruplet `(i,j,p,q)` but I don’t see where I’m doing what the Warning says I shouldn’t do, since I’m building the entire expression and evaluate it at once.
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [March 7, 2024, 6:59pm UTC](https://discourse.julialang.org/t/jump-speeding-up-constraint-violation-inspection/111303/2 "2024-03-07T18:59:20Z")
> [@HenriDeh](#):
>
> `value(2(τ[i,j]+τ[j,q]+τ[p,q]) - τ[i,j] - τ[i,p] - τ[j,p] - (8 + 6*sum(x[q,v,2] for v in TAXA if v∉(i,j,p,q))))`
Your issue is building this expression. See [Performance tips · JuMP](https://jump.dev/JuMP.jl/stable/tutorials/getting_started/performance_tips/#Use-macros-to-build-expressions)
A simple fix might be:
```julia
function inspector(model, TAXA)
τ = value.(model[:τ])
x = value.(model[:x])
triples = Dict{Int, NTuple{3,Int}}()
for q in TAXA
worst = 0
for (i,j,p) in combinations(TAXA,3)
q ∉ (i,j,p) || continue
violation = 2(τ[i,j]+τ[j,q]+τ[p,q]) - τ[i,j] - τ[i,p] - τ[j,p] - (8 + 6*sum(x[q,v,2] for v in TAXA if v∉(i,j,p,q)))
if violation < worst
worst = violation
triples[q] = (i,j,p)
end
end
end
```
Now your for loop operate on `Float64`, not JuMP expressions.