Only compute one eigenvalue instead of all#25
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duetosymmetry wants to merge 2 commits into
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barrywardell
previously approved these changes
May 27, 2020
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I'm still worried about the accuracy of switching to the Arnoldi method — the accuracy depends on the number of eigenvalues/vectors computed, and I don't know the optimal number. |
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I guess this might also need to be linked to the size of the matrix, which is also not particularly well chosen currently. |
barrywardell
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their stale review
This doesn't work as well as expected, as explained by duetosymmetry's follow up comment.
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This addresses #23. Instead of using
Eigenvalues[AMatrix]orEigensystem[AMatrix](which switch to dense methods for matrices greater than 100x100), we useEigenvalues[AMatrix, -1, ...]to sparsely compute only the desired eigenvalue. The correct eigenvalue is chosen by using the Arnoldi method, which allows aShiftargument.