# DAEProblem and ModelingToolkit.jl

**URL:** <https://discourse.julialang.org/t/daeproblem-and-modelingtoolkit-jl/127097>\
**Category:** Modelling & Simulations\
**Created:** [March 18, 2025, 2:33pm UTC](https://discourse.julialang.org/t/daeproblem-and-modelingtoolkit-jl/127097 "2025-03-18T14:33:46Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Bart\_van\_de\_Lint](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/bart_van_de_lint/32/212161_2.png) [@Bart\_van\_de\_Lint](https://discourse.julialang.org/u/Bart_van_de_Lint)\
**Post date:** [March 18, 2025, 2:33pm UTC](https://discourse.julialang.org/t/daeproblem-and-modelingtoolkit-jl/127097/1 "2025-03-18T14:33:46Z")

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I am a bit confused: should we use `DAEProblem(sys, du0, u0, tspan)` or `ODEProblem(sys, u0, tspan)` from a differential-algebraic system using `ModelingToolkit`? Using `ODEProblem` does work in my case, but then I cannot use `DAE` solvers like `DFBDF`.

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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:** [March 19, 2025, 5:08am UTC](https://discourse.julialang.org/t/daeproblem-and-modelingtoolkit-jl/127097/2 "2025-03-19T05:08:35Z")

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> [@Bart\_van\_de\_Lint](#):
>
> Using `ODEProblem` does work in my case, but then I cannot use `DAE` solvers like `DFBDF`.

There is zero benefit to using DFBDF vs FBDF and there are many downsides.

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**Author:** ![Bart\_van\_de\_Lint](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/bart_van_de_lint/32/212161_2.png) [@Bart\_van\_de\_Lint](https://discourse.julialang.org/u/Bart_van_de_Lint)\
**Post date:** [March 19, 2025, 10:00am UTC](https://discourse.julialang.org/t/daeproblem-and-modelingtoolkit-jl/127097/3 "2025-03-19T10:00:35Z")

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Good to know. Could this be made more clear in the docs?

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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:** [March 19, 2025, 11:19am UTC](https://discourse.julialang.org/t/daeproblem-and-modelingtoolkit-jl/127097/4 "2025-03-19T11:19:38Z")

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Which documentation do you think would be most useful to have this note?

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<div class="post-metadata">

**Author:** ![Bart\_van\_de\_Lint](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/bart_van_de_lint/32/212161_2.png) [@Bart\_van\_de\_Lint](https://discourse.julialang.org/u/Bart_van_de_Lint)\
**Post date:** [March 19, 2025, 11:56am UTC](https://discourse.julialang.org/t/daeproblem-and-modelingtoolkit-jl/127097/5 "2025-03-19T11:56:31Z")

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It would make sense to have an example DAEProblem, but I can’t find any tutorial on a symbolic DAEProblem, just a modelingtoolkitize-based DAEProblem… It could also make sense to add it directly in the ODESystem docstring, to make it clear that it can be used for DAESystems as well:

> **[ODESystem · ModelingToolkit.jl](https://docs.sciml.ai/ModelingToolkit/stable/systems/ODESystem/#ModelingToolkit.ODESystem)**
>
> Documentation for ModelingToolkit.jl.