# Converting GAMS to JuMP: Defining Sets
**URL:** https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875
**Category:** Optimization (Mathematical)
**Tags:** jump, constraint
**Created:** [January 16, 2024, 5:15pm UTC](https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875 "2024-01-16T17:15:41Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@sati](https://discourse.julialang.org/u/sati)
#### Post date: [January 16, 2024, 5:15pm UTC](https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875/1 "2024-01-16T17:15:41Z")
Hi all, I want to convert GAMS script to JuMP, and I have problems dealing with the sets in GAMS.
Here is the constraint in GAMS:
eDemIR(d)… demIReal(d) + sum(l,line2dem(l,d)\*lineIReal(l)) =e= 0;
l, d are sets in GAMS. l = {1,2,3} and d = {1,2,3,4,5}
What is the proper way of converting this to JuMP?
This is how I tried to define every set in the constraint:
D = [1,2,3,4,5]
L = [1,2,3]
@constraint(model, eDemIR[d in D], demIReal[d in D] + sum(line2dem[l, d] \* lineIReal[l] for l in L) == 0)
Thanks!
---
### Author:  [@hellemo](https://discourse.julialang.org/u/hellemo)
#### Post date: [January 16, 2024, 5:53pm UTC](https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875/2 "2024-01-16T17:53:50Z")
Welcome to the forum, @sati !
My GAMS skills are a bit rusty, but I guess you would want to do something like this in JuMP:
```julia
using JuMP
model = Model()
D = [1,2,3,4,5]
L = [1,2,3]
@variable(model, demIReal[D])
@variable(model, line2dem[L,D])
@variable(model, lineIReal[L])
@constraint(model, eDemIR[d in D], demIReal[d] + sum(line2dem[l, d] * lineIReal[l] for l in L) == 0)
```
---
### Author:  [@sati](https://discourse.julialang.org/u/sati)
#### Post date: [January 18, 2024, 7:31pm UTC](https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875/3 "2024-01-18T19:31:17Z")
Thanks [hellemo](https://discourse.julialang.org/u/hellemo) !
What if we have something like this:
```julia
using JuMP
model = Model()
D = [1,2,3,4,5]
L = [1,2,3]
line2dem = [1,4,3,6,5]
lineIReal = [1,2,1,1]
demIReal = [1,2,1,2]
@constraint(model, eDemIR[d in D], demIReal[d] + sum(line2dem[l, d] * lineIReal[l] for l in L) == 0)
```
is this correct ?
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [January 18, 2024, 8:07pm UTC](https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875/4 "2024-01-18T20:07:38Z")
Hi @sati, welcome to the forum.
In this example you haven’t defined any variables?
But also, no. If you run the code, you’ll get an error
```Julia
julia> @constraint(model, eDemIR[d in D], demIReal[d] + sum(line2dem[l, d] * lineIReal[l] for l in L) == 0)
ERROR: BoundsError: attempt to access 5-element Vector{Int64} at index [1, 2]
Stacktrace:
[1] getindex(::Vector{Int64}, ::Int64, ::Int64)
```
because `line2dem` is a vector:
```Julia
julia> line2dem
5-element Vector{Int64}:
1
4
3
6
5
```
but you tried to index it as if it was a matrix:
```Julia
line2dem[l, d]
```
You might want to take a look at these tutorials:
- [Getting started with Julia · JuMP](https://jump.dev/JuMP.jl/stable/tutorials/getting_started/getting_started_with_julia/)
- [Getting started with sets and indexing · JuMP](https://jump.dev/JuMP.jl/stable/tutorials/getting_started/getting_started_with_sets_and_indexing/)
---
### Author:  [@sati](https://discourse.julialang.org/u/sati)
#### Post date: [January 19, 2024, 5:44pm UTC](https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875/5 "2024-01-19T17:44:13Z")
Thanks for your answer @odow !
I edited my question to be clear. I want to convert this GAMS constraint to JuMP
…
eDemIR(d)… demIV[d] + demIReal(d) + sum(l,line2dem(l,d)\*lineIReal(l)) =e= 0;
…
l, d are sets in GAMS. l = {1,2,3} and d = {1,2,3,4,5}
In GAMS we define sets in the beginning. How can I convert this term “line2dem(l,d)” in JuMP?
What is the proper way of converting this GAMS constraint to the equivalent JuMP?
There are vectors and variables.
This is what I have:
```julia
using JuMP
model = Model()
D = [1,2,3,4,5]
L = [1,2,3]
line2dem = [1,4,3,6,5]
lineIReal = [1,2,1,1]
demIReal = [1,2,1,2]
@variable(model, demIV[D])
@constraint(model, eDemIR[d in D], demIV[d] + demIReal[d] + sum(line2dem[l, d] * lineIReal[l] for l in L) == 0)
..
..
```
Thanks.
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [January 19, 2024, 9:59pm UTC](https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875/6 "2024-01-19T21:59:59Z")
Your JuMP syntax in the `@constraint` is correct. But your input data is not correct.
What is `lin2dem`? Is it data? Is it a decision variable?
`line2dem(l,d)` looks like it is a matrix (it has two dimensions). Your definition `line2dem = [1,4,3,6,5]` is a vector. It has one dimension.
---
### Author:  [@sati](https://discourse.julialang.org/u/sati)
#### Post date: [January 27, 2024, 12:57pm UTC](https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875/7 "2024-01-27T12:57:41Z")
Thanks for your answer @odow !
Yes, line2dem is data and it’s a sparse matrix. I edited it below. So is it correct to use this matrix in the constraint? is this definition of the constraint correct?
* * *
I edited my question to be clear. I want to convert this GAMS constraint to JuMP
eDemIR(d)… demIV[d] + demIReal(d) + sum(l,line2dem(l,d)\*lineIReal(l)) =e= 0;
l, d are sets in GAMS. l = {1,2,3} and d = {1,2,3,4,5}
In GAMS we define sets in the beginning. How can I convert this term “line2dem(l,d)” in JuMP?
What is the proper way of converting this GAMS constraint to the equivalent JuMP?
There are vectors and variables.
This is what I have:
```julia
using JuMP
model = Model()
D = [1,2,3]
L = [1,2,3,4,5]
line2dem = sparse([1, 2, 3], [1, 2, 3], [1, 1, 1], 8, 3)
lineIReal = [1,2,1,1]
demIReal = [1,2,1,2]
@variable(model, demIV[D])
@constraint(model, eDemIR[d in D], demIV[d] + demIReal[d] + sum(line2dem[l, d] * lineIReal[l] for l in L) == 0)
```
Thanks.
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [January 28, 2024, 8:52pm UTC](https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875/8 "2024-01-28T20:52:18Z")
Again, your JuMP code is all correct. The constraint syntax matches the GAMS syntax.
But I get an error:
```Julia
julia> @constraint(model, eDemIR[d in D], demIV[d] + demIReal[d] + sum(line2dem[l, d] * lineIReal[l] for l in L) == 0)
ERROR: BoundsError: attempt to access 4-element Vector{Int64} at index [5]
```
because `lineIReal` is a vector with four elements:
```julia
julia> lineIReal
4-element Vector{Int64}:
1
2
1
1
```
but `L` is a set which contains `5`,
```Julia
julia> L
5-element Vector{Int64}:
1
2
3
4
5
```
so you cannot index `lineIReal[5]`.
You just need to use the right data.
---
### Author:  [@sati](https://discourse.julialang.org/u/sati)
#### Post date: [February 2, 2024, 2:14pm UTC](https://discourse.julialang.org/t/converting-gams-to-jump-defining-sets/108875/9 "2024-02-02T14:14:52Z")
Thanks @odow. The syntax and definitions are correct. These are just sample data and changing dimensions will fix.
```julia
using JuMP
model = Model()
D = [1,2,3]
L = [1,2,3,4,5]
line2dem = sparse([1, 2, 3], [1, 2, 3], [1, 1, 1], 8, 3)
lineIReal = [1,2,1,1,2]
demIReal = [1,2,1]
@variable(model, demIV[D])
@constraint(model, eDemIR[d in D], demIV[d] + demIReal[d] + sum(line2dem[l, d] * lineIReal[l] for l in L) == 0)
```