# Passing a function as an objective function in JuMP

**URL:** <https://discourse.julialang.org/t/passing-a-function-as-an-objective-function-in-jump/10745>\
**Category:** Optimization (Mathematical)\
**Tags:** jump\
**Created:** [May 6, 2018, 8:16pm UTC](https://discourse.julialang.org/t/passing-a-function-as-an-objective-function-in-jump/10745 "2018-05-06T20:16:30Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![jayce\_ram](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jayce_ram/32/3977_2.png) [@jayce\_ram](https://discourse.julialang.org/u/jayce_ram)\
**Post date:** [May 6, 2018, 8:16pm UTC](https://discourse.julialang.org/t/passing-a-function-as-an-objective-function-in-jump/10745/1 "2018-05-06T20:16:31Z")

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Anyone knows if it is possible and how to pass a function as an objective function in JuMP? I have read the documentation but i haven’t find anything about it. I have many sum as objective and I would like to write it inside a function instead of doing the conventional declaration : @objective(m, Max, “literal expression of the equation”). Something like that:

```julia
@objective(m, Max, call function() ) 

```

Thanks in advance.

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<div class="post-metadata">

**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [May 6, 2018, 10:23pm UTC](https://discourse.julialang.org/t/passing-a-function-as-an-objective-function-in-jump/10745/2 "2018-05-06T22:23:22Z")

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There is nothing stopping you from going

```julia
julia> using JuMP

julia> m=Model()
Feasibility problem with:
 * 0 linear constraints
 * 0 variables
Solver is default solver

julia> @variable(m, x)
x

julia> function foo(x)
       2x + 1
       end
foo (generic function with 1 method)

julia> @objective(m, Min, foo(x))
2 x + 1

julia> JuMP.getobjective(m)
2 x + 1

```

But, if you are building an objective with a large number of elements, this is going to be slow.

Is it really too much to use the macro? With a good data-structure and intendation, it is normally pretty easy to read. Alternatively, you could break it up into a few `@expression` objects…

```julia
julia> using JuMP

julia> m=Model()
Feasibility problem with:
 * 0 linear constraints
 * 0 variables
Solver is default solver

julia> @variable(m, x)
x

julia> @expression(m, foo, 2x + 1)
2 x + 1

julia> @objective(m, Min, foo)
2 x + 1

julia> JuMP.getobjective(m)
2 x + 1

```

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<div class="post-metadata">

**Author:** ![jayce\_ram](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jayce_ram/32/3977_2.png) [@jayce\_ram](https://discourse.julialang.org/u/jayce_ram)\
**Post date:** [May 9, 2018, 9:08am UTC](https://discourse.julialang.org/t/passing-a-function-as-an-objective-function-in-jump/10745/3 "2018-05-09T09:08:48Z")

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Thanks a lot!!