Should I report it as a bug on the github? There is currently none <https://github.com/sympy/sympy/issues?q=is%3Aissue+is%3Aopen+is_indefinite> for is_indefinite. Writing something like "is_indefinite returns error when it attempts to compute the eigenvalues. Try to import the improvments `is_positive_definite`, `is_positive_semidefinite` etc rather than `is_indefinite`, no longer attempt to compute the eigenvalues. Computing the eigenvalues symbolically is not usually possible for bigger than a 4x4 matrix due to Abel-Ruffini <https://en.wikipedia.org/wiki/Abel%E2%80%93Ruffini_theorem>. Converting to a matrix M to matrix of floats M.n() works as a workaround since then the eigenvalues can be computed approximately by mpmath."? and giving a link to this conversation?
On Thursday, May 14, 2020 at 2:47:41 PM UTC+2, JS wrote: > > Thank you. > This has worked for all matrices that I have tried. : - ) > Even M.is_positive_definite and M.is_negative_definite works. > > On Thursday, May 14, 2020 at 1:54:52 PM UTC+2, Oscar wrote: >> >> Looking at it seems that the improvements were for >> `is_positive_definite`, `is_positive_semidefinite` etc rather than >> `is_indefinite`. >> >> These cases compute fine: >> >> In [*11*]: B1.is_positive_semidefinite >> Out[*11*]: False >> >> >> In [*12*]: B1.is_negative_semidefinite >> Out[*12*]: False >> >> I think that should be enough to conclude that the matrix is indefinite. >> The improvements are that the algorithms for those cases no longer attempt >> to compute the eigenvalues. Computing the eigenvalues symbolically is not >> usually possible for bigger than a 4x4 matrix due to Abel-Ruffini: >> https://en.wikipedia.org/wiki/Abel%E2%80%93Ruffini_theorem >> >> As a workaround you can convert to a matrix of floats since then the >> eigenvalues can be computed approximately by mpmath: >> >> In [*13*]: B1.n().eigenvals() >> Out[*13*]: {-0.423518261117994: 1, 0.830838432644968: 1, >> 1.57353243409785: 1, 2.309362853398: 1, 3.91273545644822: 1, >> 4.79704908452897: 1} >> >> >> In [*14*]: B1.n().is_indefinite >> Out[*14*]: True >> >> >> -- >> Oscar >> > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/60bb1937-c309-4a54-a7c7-c30bbeec2d02%40googlegroups.com.
