Set u_modified in DAE initialization if the u was changed #1969
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Some integrators (such as Sundials) keep a shadow copy of `u` and need to reflect this copy back into the solver internals to use them. This happens e.g. during callbacks, but the same situation applies to initialization, so use the same mechanism (setting u_modified to `true`) to let the solver know that it needs to update its internal datastructures.
| @@ -183,6 +183,7 @@ function _initialize_dae!(integrator, prob::ODEProblem, alg::ShampineCollocation | |||
| integrator.u .= nlsol.u | |||
| failed = nlsol.retcode != ReturnCode.Success | |||
| end | |||
| u_modified!(integrator, true) | |||
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This is the default assumption. What's a case where this makes a difference?
|
Needs a test case |
Keno
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Sundials.jl got an implementation of the OrdinaryDiffEq DAE initialization interface in SciML#401. Unfortunately, it turns out that this doesn't quite work, because the u/du in Sundials' integrator struct are not the actual memory that IDA uses (it has an internal copy). In [1], I propose re-using `u_modified` to inform us that the shadow copy was modified during initialization. This is the Sundials side of that interface. [1] SciML/OrdinaryDiffEq.jl#1969
Keno
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Jun 17, 2023
Sundials.jl got an implementation of the OrdinaryDiffEq DAE initialization interface in SciML#401. Unfortunately, it turns out that this doesn't quite work, because the u/du in Sundials' integrator struct are not the actual memory that IDA uses (it has an internal copy). In [1], I propose re-using `u_modified` to inform us that the shadow copy was modified during initialization. This is the Sundials side of that interface. [1] SciML/OrdinaryDiffEq.jl#1969
ChrisRackauckas
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Jul 1, 2023
Sundials.jl got an implementation of the OrdinaryDiffEq DAE initialization interface in SciML#401. Unfortunately, it turns out that this doesn't quite work, because the u/du in Sundials' integrator struct are not the actual memory that IDA uses (it has an internal copy). In [1], I propose re-using `u_modified` to inform us that the shadow copy was modified during initialization. This is the Sundials side of that interface. [1] SciML/OrdinaryDiffEq.jl#1969
ChrisRackauckas
pushed a commit
to SciML/Sundials.jl
that referenced
this pull request
Jul 1, 2023
Sundials.jl got an implementation of the OrdinaryDiffEq DAE initialization interface in #401. Unfortunately, it turns out that this doesn't quite work, because the u/du in Sundials' integrator struct are not the actual memory that IDA uses (it has an internal copy). In [1], I propose re-using `u_modified` to inform us that the shadow copy was modified during initialization. This is the Sundials side of that interface. [1] SciML/OrdinaryDiffEq.jl#1969
|
I don't believe this is necessary. Specifically, setting u_modified in inits is only needed for Sundials solvers, and sundials solvers don't use ODE/DAEIntegrator so these initialization methods will never be used with them, |
That's true, but only by default, there's nothing preventing people from setting these manually or chaining them, but even if nobody were to ever do that, that's not really the point. The question is whether the interface requires these to be set and as written, the answer is yes. |
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Some integrators (such as Sundials) keep a shadow copy of
uand need to reflect this copy back into the solver internals to use them. This happens e.g. during callbacks, but the same situation applies to initialization, so use the same mechanism (setting u_modified totrue) to let the solver know that it needs to update its internal datastructures.