# Callback on Internal Stages of TSIT5

**URL:** https://discourse.julialang.org/t/callback-on-internal-stages-of-tsit5/102415
**Category:** General Usage
**Created:** [August 2, 2023, 6:48pm UTC](https://discourse.julialang.org/t/callback-on-internal-stages-of-tsit5/102415 "2023-08-02T18:48:53Z")
**Posts on this page:** 1
**Page:** 2

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### Author: ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [August 5, 2023, 1:55pm UTC](https://discourse.julialang.org/t/callback-on-internal-stages-of-tsit5/102415/22 "2023-08-05T13:55:28Z")

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> [@yoshi](#):
>
> Where in the code is the tsit5 code implemented and where is integ.k loaded? Or if you don’t know off the top of your head, where would you start looking?

You’d make modifications right here:

> <https://github.com/SciML/OrdinaryDiffEq.jl/blob/master/src/perform_step/low_order_rk_perform_step.jl#L770-L823>

If you want a version that’s more plyable for playing with, you may be interested in SimpleDiffEq.jl

> <https://github.com/SciML/SimpleDiffEq.jl/blob/master/src/tsit5/gpuatsit5.jl#L104-L223>

The barebones version for GPU kernels is a rather nice version for hacking to do weird things.

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