# How to make \`step!(integrator)\` overcome initial stiffness issues

**URL:** <https://discourse.julialang.org/t/how-to-make-step-integrator-overcome-initial-stiffness-issues/118115>\
**Category:** Modelling & Simulations\
**Tags:** question, ode\
**Created:** [August 13, 2024, 2:05am UTC](https://discourse.julialang.org/t/how-to-make-step-integrator-overcome-initial-stiffness-issues/118115 "2024-08-13T02:05:47Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![SteffenPL](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/steffenpl/32/206270_2.png) [@SteffenPL](https://discourse.julialang.org/u/SteffenPL)\
**Post date:** [August 13, 2024, 2:05am UTC](https://discourse.julialang.org/t/how-to-make-step-integrator-overcome-initial-stiffness-issues/118115/1 "2024-08-13T02:05:47Z")

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Related to [my previous question](https://discourse.julialang.org/t/parallel-adaptive-time-stepping-for-ode-problems-at-different-time-scales/117982), I now run into an issue with the `step!` interface.

Sorry that I didn’t manage to create a MWE, if needed I will try harder 😉

At the moment, I am in a situation where for exactly the same SDE/ODE problem `solve(prob)` works, but `step!(prob, tspan[end])` does not work, due to `dt` becoming too small in the very first time-step. (Notably, the solution produced by `solve` uses time steps that are larger than `admin.`)

Is there a well known trick to make the integrator interface treat a step like an initial step?

(Anyway, I get that the question is ill-posed. Let me know if I need to add more details.)

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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 17, 2024, 3:45pm UTC](https://discourse.julialang.org/t/how-to-make-step-integrator-overcome-initial-stiffness-issues/118115/2 "2024-08-17T15:45:46Z")

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I cannot fully parse the question 😅 An MWE might be needed.

“Initial stiffness” is this with MTK? Do you mean at exactly time zero you have some singularity?