# Optim callback function -- how to use optimization variable

**URL:** <https://discourse.julialang.org/t/optim-callback-function-how-to-use-optimization-variable/8807>\
**Category:** Optimization (Mathematical)\
**Tags:** optim\
**Created:** [February 4, 2018, 12:26pm UTC](https://discourse.julialang.org/t/optim-callback-function-how-to-use-optimization-variable/8807 "2018-02-04T12:26:03Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![egcjm](https://avatars.discourse-cdn.com/v4/letter/e/5fc32e/32.png) [@egcjm](https://discourse.julialang.org/u/egcjm)\
**Post date:** [February 4, 2018, 12:26pm UTC](https://discourse.julialang.org/t/optim-callback-function-how-to-use-optimization-variable/8807/1 "2018-02-04T12:26:03Z")

</div>

The optim callback function seems to operate on the OptimizationState, which provides access to the iteration count (.iteration) and value. Can I access the optimization variable being optimized (i.e. temporary optim.minimizer(res)) ?

---

<div class="post-metadata">

**Author:** ![piever](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/piever/32/1815_2.png) [@piever](https://discourse.julialang.org/u/piever)\
**Post date:** [January 26, 2021, 4:45pm UTC](https://discourse.julialang.org/t/optim-callback-function-how-to-use-optimization-variable/8807/2 "2021-01-26T16:45:50Z")

</div>

A bit late to the party, but I’ve replied to the same question [here](https://discourse.julialang.org/t/optim-jl-callback/52625/2). (Adding a cross-ref in case somebody searches for the question online and ends up here.)