# How to use the solver-dependent callback

**URL:** <https://discourse.julialang.org/t/how-to-use-the-solver-dependent-callback/76519>\
**Category:** Optimization (Mathematical)\
**Tags:** question\
**Created:** [February 16, 2022, 12:17am UTC](https://discourse.julialang.org/t/how-to-use-the-solver-dependent-callback/76519 "2022-02-16T00:17:32Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![Jacob\_Jin](https://avatars.discourse-cdn.com/v4/letter/j/c0e974/32.png) [@Jacob\_Jin](https://discourse.julialang.org/u/Jacob_Jin)\
**Post date:** [February 16, 2022, 12:58am UTC](https://discourse.julialang.org/t/how-to-use-the-solver-dependent-callback/76519/3 "2022-02-16T00:58:50Z")

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Hi, thank you for you timely reply. I have viewed the page and know how to post a question more efficiently.

I have another question: how to retrieve the UnbdRay in Julia. Indeed, there is a quite similar question but no solution:

> [@How to use Gurobi Attributes in Julia](https://discourse.julialang.org/t/how-to-use-gurobi-attributes-in-julia/25529):
>
> Hi, I am trying to use one Gurobi attribute (UnbdRay, [UnbdRay](https://www.gurobi.com/documentation/8.1/refman/unbdray.html#attr:UnbdRay)) but I am unable to find the macro to be used in Gurobi. Below is an example I am trying to use SP=Model(solver=GurobiSolver(InfUnbdInfo=1)) status= unbound Now I am trying below macros to get unbound ray getUnbdRay(SP) below is the error ERROR: UndefVarError: getUnbdRay not defined Can anyone please help me how to call the attributes of Gurobi in Julia. Thank you. Vikas

Thank you so much!!!

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