# InexactError in Callback
**URL:** https://discourse.julialang.org/t/inexacterror-in-callback/102648
**Category:** Optimization (Mathematical)
**Tags:** jump
**Created:** [August 9, 2023, 5:27pm UTC](https://discourse.julialang.org/t/inexacterror-in-callback/102648 "2023-08-09T17:27:37Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@jack\_lee](https://discourse.julialang.org/u/jack_lee)
#### Post date: [August 9, 2023, 5:27pm UTC](https://discourse.julialang.org/t/inexacterror-in-callback/102648/1 "2023-08-09T17:27:37Z")
When I learn the [user-cut](https://jump.dev/JuMP.jl/stable/tutorials/linear/callbacks/) callback function ,I rewrite the code below:
```julia
function user_cut()
Random.seed!(13)
N = 30
capacity = 10
weights,values = rand(N),rand(N)
model = Model(GLPK.Optimizer)
@variable(model,x[1:N],Bin)
@constraint(model,weights' * x <= capacity)
@objective(model,Max,x' * values)
function call_back(cb_data)
x_val = callback_value.(cb_data,x)
total = weights' * x_val
println("callback total : $(total)")
# num = sum(1 for i in 1:N if x_val[i] > 1e-4)
num = sum(Int,x_val)
if total > capacity
con = @build_constraint(sum(x) <= num - 1)
println("add $(con)")
MOI.submit(model,MOI.UserCut(cb_data),con)
end
end
set_attribute(model,MOI.UserCutCallback(),call_back)
optimize!(model)
sum(value.(x))
end
```
This is the official code:
```julia
num = sum(1 for i in 1:N if x_val[i] > 1e-4)
```
But When I change it to :
```julia
sum(Int,x_val)
```
It raised error:
```julia
callback total : 10.0
InexactError: Int64(23.047802735569988)
```
Can somebody explain why?
---
### Author:  [@contradict](https://discourse.julialang.org/u/contradict)
#### Post date: [August 9, 2023, 5:59pm UTC](https://discourse.julialang.org/t/inexacterror-in-callback/102648/2 "2023-08-09T17:59:32Z")
You are requesting conversion from a Float64 to an Int64 and no exact [conversion](https://docs.julialang.org/en/v1/base/base/#Core.InexactError) exists.
```julia
julia> Int(23.0478)
ERROR: InexactError: Int64(23.0478)
Stacktrace:
[1] Int64(x::Float64)
@ Base ./float.jl:900
[2] top-level scope
@ REPL[33]:1
julia> Int(23.0)
23
```
Perhaps you mean
```julia
num = sum(trunc, x_val)
```
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [August 10, 2023, 8:49pm UTC](https://discourse.julialang.org/t/inexacterror-in-callback/102648/3 "2023-08-10T20:49:23Z")
Other options are `num = sum(x_val .> 1e-4)` or `num = sum(round.(Int, x_val))`.
But really, there’s nothing wrong with what you wrote to begin with.