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Add Rosenbrock integrators#479

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alexander-novo wants to merge 44 commits into
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alex/rosenbrock
Open

Add Rosenbrock integrators#479
alexander-novo wants to merge 44 commits into
developfrom
alex/rosenbrock

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@alexander-novo

@alexander-novo alexander-novo commented Jul 7, 2026 •
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Description

Add Rosenbrock integrators, which are lighter-weight alternatives to IDA that work well with co-simulation.

Proposed changes

The current version depends on ReSolve and needs porting work to be used with GridKit vectors. The operations used by the Rosenbrock integrators are:

vector_handler_.scal();
vector_handler_.axpy();
vector_handler_.abs();
vector_handler_.max();
vector_handler_.diagSolve();
vector_handler_.amax();

This PR also need's ReSolve's SystemSolver to be ported.

As well, I think some more testing wouldn't go amiss... An integration test on an example power grid would work nicely.

Checklist

  • All tests pass.
  • Code compiles cleanly with flags -Wall -Wpedantic -Wconversion -Wextra.
  • The new code follows GridKit™ style guidelines.
  • There are unit tests for the new code.
  • The new code is documented.
  • The feature branch is rebased with respect to the target branch.
  • I have updated CHANGELOG.md to reflect the changes in this PR. If this is a minor PR that is part of a larger fix already included in the file, state so.

Further comments

@alexander-novo alexander-novo requested a review from pelesh July 7, 2026 17:42
@alexander-novo alexander-novo self-assigned this Jul 7, 2026
@alexander-novo alexander-novo added the enhancement New feature or request label Jul 7, 2026
@pelesh pelesh added this to the Release 0.2 milestone Jul 8, 2026
@pelesh pelesh mentioned this pull request Jul 8, 2026
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pelesh
pelesh reviewed Jul 8, 2026
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@pelesh pelesh left a comment

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This is really nice work!

I would suggest merging #480 first and then rebasing so that we avoid introducing Re::Solve dependency.

Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp
Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp
Comment thread GridKit/Solver/Dynamic/RosenbrockTableaus.cpp Outdated
@alexander-novo alexander-novo requested a review from pelesh July 9, 2026 00:11
@alexander-novo

alexander-novo commented Jul 9, 2026

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@pelesh I've updated the PR to make use of GridKit's own Vector and VectorHandler. Re::Solve is still used for the lienar solver part, however (see Rosenbrock::time_step)

@alexander-novo alexander-novo changed the base branch from develop to slaven/vector-handler July 9, 2026 00:25
@pelesh

pelesh commented Jul 9, 2026

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@pelesh I've updated the PR to make use of GridKit's own Vector and VectorHandler. Re::Solve is still used for the lienar solver part, however (see Rosenbrock::time_step)

Using a linear solver from Re::Solve is a good thing :). We can add bare KLU interface in a separate PR, if needed.

alexander-novo and others added 17 commits July 9, 2026 12:30
shakedregev
shakedregev reviewed Jul 9, 2026
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Comment thread GridKit/Solver/Dynamic/RosenbrockTableaus.cpp Outdated
shakedregev
shakedregev reviewed Jul 9, 2026
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Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp
shakedregev
shakedregev reviewed Jul 9, 2026
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Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp
shakedregev
shakedregev reviewed Jul 9, 2026
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Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp Outdated
shakedregev
shakedregev reviewed Jul 9, 2026
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Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp
shakedregev
shakedregev reviewed Jul 9, 2026
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Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp Outdated
shakedregev
shakedregev reviewed Jul 10, 2026
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Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp
shakedregev
shakedregev reviewed Jul 10, 2026
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Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp Outdated
shakedregev
shakedregev reviewed Jul 10, 2026
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Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp Outdated
shakedregev
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Comment thread tests/UnitTests/Solver/Dynamic/RosenbrockTests.hpp
shakedregev
shakedregev approved these changes Jul 10, 2026
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Fix the minor issues and good to merge. I tested it.

nkoukpaizan
nkoukpaizan reviewed Jul 10, 2026
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Comment thread tests/UnitTests/Solver/Dynamic/CMakeLists.txt Outdated
Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp Outdated
Comment thread README.md Outdated
@nkoukpaizan nkoukpaizan mentioned this pull request Jul 10, 2026
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nkoukpaizan
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Comment thread GridKit/Solver/Dynamic/RosenbrockTableaus.cpp Outdated
Comment thread GridKit/Solver/Dynamic/RosenbrockTableaus.cpp Outdated
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nkoukpaizan reviewed Jul 10, 2026
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Comment thread tests/UnitTests/Solver/Dynamic/CMakeLists.txt Outdated
pelesh
pelesh reviewed Jul 12, 2026
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Very nice compact implementation.

Before merging it would be helpful to create clear interfaces between Rosenbrock integrator and GridKit and between Rosenbrock integrator and linear solver.

Also, please implement each class/structure in a separate source/header files.

Comment thread GridKit/MemoryUtilities/ResolveMemoryUtils.hpp
Comment on lines +11 to +15
/**
* @brief Converts a GridKit \ref MemorySpace to its corresponding Re::Solve MemorySpace
*
*/
inline ReSolve::memory::MemorySpace memorySpaceAsResolve(MemorySpace memspace)

@pelesh pelesh Jul 12, 2026

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This should not be necessary. GridKit should not see Re::Solve memory space and vice versa.

Comment thread GridKit/Solver/Dynamic/Rosenbrock.hpp
Comment on lines +28 to +30
template <typename RealT>
struct StepControl
{

@pelesh pelesh Jul 12, 2026

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This structure and everything that is not Rosenbrock class should be in separate file. For each class or structure there should be a separate *.hpp and *.cpp files.

Comment thread GridKit/Solver/Dynamic/Rosenbrock.hpp
Comment on lines +50 to +52
template <typename RealT>
class StepController
{

@pelesh pelesh Jul 12, 2026

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Same here. Please move this to a separate file.

Comment thread GridKit/Solver/Dynamic/Rosenbrock.hpp
Comment on lines +498 to +500
ReSolve::SystemSolver& lin_solver,
GridKit::LinearAlgebra::VectorHandler<ScalarT, IdxT>& vector_handler,
const ErrorNorm<ScalarT, IdxT>* err_norm,

@pelesh pelesh Jul 12, 2026

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VectorHandler and ErrorNorm probably should be members of Rosenbrock class. I am not sure why these are passed as constructor parameters.

Comment thread GridKit/Solver/Dynamic/Rosenbrock.hpp
Comment on lines +610 to +617
/**
* @brief A simple textbook adaptive `StepController` which seeks to meet a relative and absolute tolerance
* based on an error estimate.
*
*/
template <typename RealT>
class AdaptiveStep : public StepController<RealT>
{

@pelesh pelesh Jul 12, 2026

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This class should be in a separate file.

Comment thread GridKit/Solver/Dynamic/RosenbrockTableaus.cpp
Comment on lines +7 to +10
template <class ScalarT, typename IdxT>
Rosenbrock<ScalarT, IdxT>::Tableau Rosenbrock<ScalarT, IdxT>::Tableau::linImplicitEuler()
{
constexpr size_t num_stages = 1;

@pelesh pelesh Jul 12, 2026

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I would keep tableaus in the Rosenbrock.cpp file.

Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp
Comment on lines +995 to +996
InfNorm<ScalarT, IdxT>::RealT InfNorm<ScalarT, IdxT>::errorNorm(State& err, State& y, State& yprev, GridKit::LinearAlgebra::VectorHandler<ScalarT, IdxT>& handler, ReSolve::memory::MemorySpace memspace) const
{

@pelesh pelesh Jul 12, 2026

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Re::Solve memory space should not show up here. It is internal to Re::Solve and should not be used in GridKit's VectorHandler.

Comment thread GridKit/Solver/Dynamic/Rosenbrock.cpp
Comment on lines +270 to +271
resolve_rhs_ = std::make_unique<ReSolve::vector::Vector>(size);
resolve_lhs_ = std::make_unique<ReSolve::vector::Vector>(size);

@pelesh pelesh Jul 12, 2026

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Re::Solve vector should not appear in Rosenbrock class.

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Reviewers

@pelesh pelesh pelesh left review comments
@shakedregev shakedregev shakedregev approved these changes
@nkoukpaizan nkoukpaizan nkoukpaizan left review comments
@Steven-Roberts Steven-Roberts Awaiting requested review from Steven-Roberts

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@alexander-novo alexander-novo

Labels

enhancement New feature or request new solver

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4 participants

@alexander-novo @pelesh @shakedregev @nkoukpaizan