Initial Implementation of Subsystem Model for Partition Simulation by abdourahmanbarry · Pull Request #492 · ORNL/GridKit

abdourahmanbarry · 2026-07-16T04:47:51Z

Description

In this PR, we introduce the initial implementation of the SubsystemModel for partitioned Power Electronics simulation. The implementation provides the infrastructure required to partition Power Electronic networks, and to evaluate subsystem residuals and Jacobians independently. This lays the foundation for implementing co-simulation methods in future pull requests.

Proposed changes

We added a SubsystemModel class to represent an individual partition and a BusPartitionInterface component to mark partition boundaries.
Implemented residual and Jacobian evaluation for subsystem models.
Added support for user-defined coupling functions required for solving subsystems with multi-stage co-simulation methods.

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.

abdourahmanbarry · 2026-08-06T05:57:56Z

This pull request is ready for review.

…es. During partitioning: - BusPartitionInterface connects to the bus partition - ComponentPartitionInterface connects to the component partition

…ample more rebust

…ion interfaces

- Improved subsystem residual and Jacobian validation against the full-system model. - Updated BusPartitionInterface to support arbitrary ordering of internal and external component variables. - Added ownership and cleanup of copied components used by partition interfaces. - Improved comments and documentation for partitioning, Jacobian verification, and interface behavior.

nkoukpaizan

I few initial comments on the Hires example. I'll take a closer look at the partition interface after comments by @alexander-novo have been addressed.

- add documentation for hires problem and partitioning - test subsystem jacobian and residuals - Update CMake file

- Add comments to methods and lambda functions - added check to ensure only allocated components can be added to model - Change parameter type in addInterface method to PartitionInterface

- Partition interface can be applied to all bus types, not just MicrogridBus - New clone functionality allows users to pass components directly without explicitly copying it - Update CMake file with dense vector dependency - Add more documentation - Move suitable code from constructor to allocate

- move microgrid network builder section to separate file to facilitate code reuse as more examples dependent on it - Add partition utility code to minimize code duplication in partition examples. - Added all helper header files in one location - Remove remaining Hires example files from Partition folder

- Refactored common code in the Microgrid, ScaleMicrogrid, and ScaleMicrogridArbitrary examples into reusable helper functions - Improved documentation across the PowerElectronics examples - Updated CMake files

- Minor format changes - Updated tests and added documentation for partition interface and SubsystemModel - Used size_t for some loops in CircuitComponent

nkoukpaizan

Overall nice work!

In addition to the specific comments below:

With the growing size of this PR, you might want to isolate some of the changes into small PRs that we can quickly review and merge.
Please rebase, so CI runs. You might want to hold off on updating CHANGELOG.md until it's closer to ready to merge to reduce the need to rebase.
We need to better document how clone() and forcing_data work and how syncing might occur in simulations.
I am getting a test failure. Loosening the tolerance would be reasonable, as long as the error sources are well understood and documented.

11: Partition Microgrid Validation
11: ------------------------------
11: Maximum residual error:         2.313046080415393e-14
11: Machine epsilon:                2.220446049250313e-16
11: Residuals matched:              False
1/1 Test #11: PartitionMicrogrid ...............***Failed    0.06 sec

nkoukpaizan · 2026-08-23T23:02:54Z

+          auto isEqual = [&tolerance](RealT value, RealT reference)
+          {
+            if (tolerance)
+            {
+              return GridKit::Testing::isEqual(value, reference, *tolerance);
+            }
+
+            return GridKit::Testing::isEqual(value, reference);
+          };


I would set the default tolerance for the helper to machine precision and always pass it to GridKit::Testing::isEqual. That would remove the need for this lambda.

nkoukpaizan · 2026-08-23T23:08:07Z

@@ -0,0 +1,309 @@
+// MicrogridNetwork.hpp


This is a welcome change! Consider isolating this into a quick PR to facilitate review and narrow the scope of this one.

nkoukpaizan · 2026-08-23T23:18:57Z

+      IdxT part_size = q + (j < r ? 1 : 0);
+      IdxT end       = std::min(index + part_size, num_ibrs);
+
+      // Add all components belonging to this partition.
+      for (; index < end; ++index)


Some documentation would be helpful for this logic. Consider writing more explicitly.

nkoukpaizan · 2026-08-23T23:21:05Z

+\left(\frac{dy_4}{dt}+y_4\right)
+\left(0.1y_4-8.32y_2-1.71y_3\right)
+0.02y_4,
+\\[6pt]


Some rendering issues on GH.

nkoukpaizan · 2026-08-23T23:24:43Z

+    // line vector params
+    // Every odd line has the same parameters and every even line has the same parameters
+    real_type              rline1 = 0.23;
+    real_type              Lline1 = 0.1 / (2.0 * M_PI * 50.0);


M_PI --> std::numbers::pi_v<RealT> to be consistent with recent changes (#521), though we don't have to be as strict in examples/.

nkoukpaizan · 2026-08-24T00:11:12Z

+      if (other.jacobian_coo_rows_)
+      {
+        jacobian_coo_rows_ = std::make_unique<IdxT[]>(static_cast<size_t>(nnz_));
+
+        for (IdxT i = 0; i < nnz_; ++i)
+        {
+          jacobian_coo_rows_[static_cast<size_t>(i)] = other.jacobian_coo_rows_[static_cast<size_t>(i)];
+        }
+      }
+
+      /*
+       * Deep-copy the COO Jacobian column indices.
+       */
+      if (other.jacobian_coo_cols_)
+      {
+        jacobian_coo_cols_ = std::make_unique<IdxT[]>(static_cast<size_t>(nnz_));
+
+        for (IdxT i = 0; i < nnz_; ++i)
+        {
+          jacobian_coo_cols_[static_cast<size_t>(i)] = other.jacobian_coo_cols_[static_cast<size_t>(i)];
+        }
+      }
+
+      /*
+       * Deep-copy the COO Jacobian values.
+       */
+      if (other.jacobian_coo_values_)
+      {
+        jacobian_coo_values_ = std::make_unique<RealT[]>(static_cast<size_t>(nnz_));
+
+        for (IdxT i = 0; i < nnz_; ++i)
+        {
+          jacobian_coo_values_[static_cast<size_t>(i)] = other.jacobian_coo_values_[static_cast<size_t>(i)];
+        }
+      }
+
+      if (size_ > 0)
+      {
+        y_ext_  = std::make_unique<const ScalarT*[]>(static_cast<size_t>(size_));
+        yp_ext_ = std::make_unique<const ScalarT*[]>(static_cast<size_t>(size_));
+        f_ext_  = std::make_unique<ScalarT*[]>(static_cast<size_t>(size_));
+
+        for (IdxT i = 0; i < size_; ++i)
+        {
+          y_ext_[i]  = nullptr;
+          yp_ext_[i] = nullptr;
+          f_ext_[i]  = nullptr;
+        }
+      }
+
+      // State, state derivative, residual, and absolute tolerance.
+      copyVector(y_, other.y_);
+      copyVector(yp_, other.yp_);
+      copyVector(f_, other.f_);
+      copyVector(abs_tol_, other.abs_tol_);
+      copyVector(g_, other.g_);
+      copyVector(yB_, other.yB_);
+      copyVector(ypB_, other.ypB_);
+      copyVector(fB_, other.fB_);
+      copyVector(gB_, other.gB_);
+      copyVector(param_, other.param_);
+      copyVector(param_up_, other.param_up_);
+      copyVector(param_lo_, other.param_lo_);


I would expect the cloning and syncing of the states to be different operations. One would need to keep things synced as the simulation progresses.

nkoukpaizan · 2026-08-24T00:26:52Z

+#include <GridKit/Model/PowerElectronics/SystemModelPowerElectronics.hpp>
+#include <GridKit/ScalarTraits.hpp>
+
+namespace GridKit


Please add a @todo item for namespace PowerElectronics. I see this applies to all PowerElectronics models. A quick PR for this update would be nice too!

nkoukpaizan · 2026-08-24T00:30:19Z

+          if (!is_internal_entry)
          {
-            vals[map_to_csr_[counter]] += v[i];
-            ++counter;
+            continue;
          }
+
+          vals[map_to_csr_[counter]] += v[i];
+          ++counter;


This is clearer to me. Multiple instances of this.

Suggested change

if (!is_internal_entry)

{

vals[map_to_csr_[counter]] += v[i];

++counter;

continue;

}

vals[map_to_csr_[counter]] += v[i];

++counter;

if (is_internal_entry)

{

vals[map_to_csr_[counter]] += v[i];

++counter;

}

nkoukpaizan · 2026-08-24T00:33:43Z

+{
+
+  template <class ScalarT, typename IdxT>
+  class SubsystemModel : public PowerElectronicsModel<ScalarT, IdxT>


Please add a todo to make the names more intuitive, potentially renaming the base class.

nkoukpaizan · 2026-08-24T00:45:00Z

+    /**
+     *@brief Maps global system indices to local subsystem indices for internal variables.
+     */
+    std::unordered_map<IdxT, IdxT> internal_map_;
+
+    /**
+     * @brief Maps global system indices to local subsystem indices for external variables.
+     */
+    std::unordered_map<IdxT, IdxT> external_map_;
+
+    /**
+     * @brief Global system index corresponding to each entry in the external subsystem vectors.
+     */
+    std::vector<IdxT> external_data_indices_;
+
+    /**
+     * @brief subsystem external State, derivative, and residual vectors.
+     */
+    std::vector<ScalarT> y_ext_data_;
+
+    /**
+     * @brief subsystem external derivative
+     */
+    std::vector<ScalarT> yp_ext_data_;
+
+    /**
+     * @brief subsystem external derivative
+     */
+    std::vector<ScalarT> f_ext_data_;


Can't we use the same storage types as the base classes, e.g., GridKit::LinearAlgebra::Vector?

abdourahmanbarry force-pushed the abdou/partitioning_microgrid branch from 85a516d to 01a410b Compare July 19, 2026 08:27

abdourahmanbarry self-assigned this Jul 23, 2026

abdourahmanbarry force-pushed the abdou/partitioning_microgrid branch from 66c58ad to b48a401 Compare July 24, 2026 02:46

abdourahmanbarry requested review from nkoukpaizan and pelesh July 24, 2026 05:17

abdourahmanbarry force-pushed the abdou/partitioning_microgrid branch from a375b1f to f65baeb Compare August 3, 2026 05:16

abdourahmanbarry requested a review from alexander-novo August 6, 2026 05:52

abdourahmanbarry marked this pull request as ready for review August 6, 2026 05:57

pelesh added enhancement New feature or request new solver labels Aug 7, 2026

pelesh added this to the Release 0.3 milestone Aug 7, 2026

alexander-novo requested changes Aug 11, 2026

View reviewed changes

abdourahmanbarry force-pushed the abdou/partitioning_microgrid branch from e96184a to 98be2e0 Compare August 11, 2026 18:28

abdourahmanbarry added 16 commits August 11, 2026 18:37

Work in progress code for cosim integration

547cac8

Added partition interfaces to power electronics and updated cmake fil…

7463300

…es. During partitioning: - BusPartitionInterface connects to the bus partition - ComponentPartitionInterface connects to the component partition

Made minor changes to partition interface code

ea84ec5

Updated Hires test problem to implicit form

2dd8fe8

Change comments in partition interfaces

a0b7a50

Added a subsystem model for evaluating partitions

82c0efc

Added a partitioned microgrid test problem

d5d84c5

Updated bus partition interface to work with new SubsystemModel

1a8ba04

Work in progress cosimulation implementation: in rought shape

c9c64f2

Cleaned up code in subsystem and made the partition microgrid test ex…

9692e57

…ample more rebust

First attempt at arbitrary partitioning

9950483

Added microgrid with four partitions

3609340

first version of subsystem

5ef63d3

Added partitioned scale microgrid example

c60ba33

Rmoved obsolete interfaces and clean up partitioning code

89ee325

Partition Scale Microgrid configured with 10000IBRs

1e99fc3

abdourahmanbarry and others added 10 commits August 11, 2026 18:37

Updated examples to reflect new changes in subsystem model and partit…

96ac403

…ion interfaces

Apply pre-commit fixes

4ce744b

Addressed leaks

1887bf0

Update partitioning code to use the no-copy implementation from develop

19a0a6f

Apply pre-commit fixes

7fa22d6

Apply pre-commit fixes

2e360d9

Update ChangeLog file

838af48

Remove co-simulation changes for separate pull request

c8a6dcb

Removed PartitionEvaluator

f082543

abdourahmanbarry force-pushed the abdou/partitioning_microgrid branch from 98be2e0 to f082543 Compare August 11, 2026 18:52

abdourahmanbarry and others added 2 commits August 11, 2026 22:32

Updated hires test problems

6bb5472

Apply pre-commit fixes

367e193

alexander-novo reviewed Aug 11, 2026

View reviewed changes

Comment thread examples/PowerElectronics/Partition/PartitionHires.cpp Outdated

nkoukpaizan reviewed Aug 13, 2026

View reviewed changes

abdourahmanbarry added 10 commits August 15, 2026 13:40

Moved Hires test problem to tests folder

d87215d

- add documentation for hires problem and partitioning - test subsystem jacobian and residuals - Update CMake file

Add more documentation for SubsystemModel

7628dc5

- Add comments to methods and lambda functions - added check to ensure only allocated components can be added to model - Change parameter type in addInterface method to PartitionInterface

Add clone function to components in PowerElectronics

f5c2134

Add tests for component clone method

9053f17

Fixed failing test

9f85ee1

Cleaned up Microgrid examples

54af398

- Refactored common code in the Microgrid, ScaleMicrogrid, and ScaleMicrogridArbitrary examples into reusable helper functions - Improved documentation across the PowerElectronics examples - Updated CMake files

Clean up

938a7ff

Update and Clean up partitioning code

2ed1b83

- Minor format changes - Updated tests and added documentation for partition interface and SubsystemModel - Used size_t for some loops in CircuitComponent

pelesh requested a review from hambrickjc August 17, 2026 18:35

superwhiskers self-requested a review August 20, 2026 19:12

nkoukpaizan requested review from alexander-novo and nkoukpaizan August 23, 2026 18:06

nkoukpaizan reviewed Aug 24, 2026

View reviewed changes

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Description

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Checklist

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abdourahmanbarry commented Aug 6, 2026

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