Some Birkhoff constraints are now treated as linear.

[robfalck]

Summary

The dense block in the Birkhoff transcription's sparsity pattern is due to a matrix used to compute the state defects as a function of the state rates. This matrix is constant and, as long as the states are a design variable, this constraint is linear.

Making this constraint linear significantly improves the sparsity coloring for the Phase. The Birkhoff transcription maintains the sparsity, and good conditioning, even when the number of nodes is extremely high.

Related Issues

• Resolves #1041

Backwards incompatibilities

None

New Dependencies

None