Change MassMatricDAE splitting of algebraic states and differential states - #259
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williampiat3 wants to merge 8 commits into
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williampiat3 wants to merge 8 commits into
williampiat3 wants to merge 8 commits into
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Added handling for differential and algebraic equations in the mass matrix.
williampiat3
changed the title
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I read the Contributing.md but a PR allows to have a code change to illustrate and discuss. |
Added test for nonsymmetric singular mass matrix in MassMatrixDAE.
Author
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There was an error in the test but actually it was normal since this was a case that I wanted MassMatrixDAE to handle (having a non symmetric and singular "mass" matrix) |
Refactor mass matrix handling to use pseudoinverse for rectangular systems and streamline Jacobian calculations.
Refactor mass matrix solver to use SVD for stability.
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Tests are passing now locally |
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Summary
I am trying to use MassMatrixDAE in a collaborative effort to make this PR: pathsim/pathsim-rf#6
We ran into an issue: MassMatrixDAE separates the algebraic states and the differential states by checking the presence of differential terms in the rows of the system M.
However this is essentially incorrect: rows in M describe the equations, columns describe state coefficients. Therefore in order to identify differential variables one needs to check the presence of terms following the columns.
Our system M is essentially non symmetric this is why this issue happened, usually Mass Matrices are symmetric making dealing with rows and columns the same
As far as I have seen lu_factor and lu_solve can handle the rectangular case, we will see soon if it breaks the tests ^^
Changes
handle differently rows and columns to split correctly differential states and algebraic states
Test plan