There have been some recent improvements to the code handling this
which you could try out by installing the pre-release of 1.6 with pip:
pip install -U --pre sympy
--
Oscar
On Thu, 14 May 2020 at 09:07, JS <jakub.sko...@gmail.com> wrote:
>
> Hello,
> I have run into a problem with various matrices. I have read Gotchas and
> Pitfalls and tried to search around, but I was unable to find anything
> relevant.
>
> For some matrices M, the M.is_indefinite simply returns no output. I have
> noticed that M.eigenvals() works for on these matrices, however,
> M.diagonalize() runs for more than a minute before it gives an output.
> Matrices that have caused this problem for me:
> M1 = Matrix(([4, 2, sqrt(3)], [2, 2, 0], [sqrt(3), 0, 1] ))
> M1.is_indefinite
>
> M2 = Matrix(([4, 2, 1], [2, 2, 0], [1, 0, 1] ))
> M2.is_indefinite
>
> M3 = Matrix(([14, -9, 0], [-9, 32, 30], [0, 30, 1]))
> M3.is_indefinite
>
> M4 = Matrix(([1, -4, -6], [-4, 2, 3], [-6, 3, 8] ))
> M4.is_indefinite
> Link to SymPy Live output.
>
>
>
> Some bigger matrices B returns error
> # Since 'simplify' flag is unsupported in roots() MatrixError: Could not
> compute eigenvalues for Matrix
> when using B.is_indefinite, when I use B.is_indefinite. I get same kind of
> error for B.eigenvals() and B.diagonalize().
>
> Matrices that have caused this problem for me:
> B1 = Matrix(([3, -1, 1, 1, 0, 0], [-1, 2, 0, 1, 0, 0], [1, 0, 1, 0, 0, 0],
> [1, 1, 0, 1, 1, 0], [0, 0, 0, 1, 4, 1], [0, 0, 0, 1, 1, 2] ))
> B1.is_indefinite
> B1.eigenvals()
> B1.diagonalize()
>
> B2 = Matrix([[12, -4, 4, 3, 1, 0], [-4, 6, -1, 2, 1, 0], [4, -1, 2, 1, 0, 0],
> [3, 2, 1, 5, 6, 3], [1, 1, 0, 6, 18, 6], [0, 0, 0, 3, 6, 5]]) # this is in
> fact L2 = L1.T*L1
> B2.is_indefinite
> B2.eigenvals()
> B2.diagonalize()
>
> B3 = Matrix(([1, -1, 1, 0, 0, 1], [-1, 2, 1, 0, 2, 0], [1, 1, 6, 2, 3, 0],
> [0, 0, 2, 1, 4, 0], [0, 2, 3, 4, 5, 1], [1, 0, 0, 0, 1, 2] ))
> B3.is_indefinite
> B3.eigenvals()
> B3.diagonalize()
> Link to SymPy Live output.
>
> I have this problem on my Linux machine (SymPy 1.5.1, Python 3.8.2-64-bit) as
> well as on the SymPy Live (SymPy 1.5.1, Python 2.7.12).
>
> Please, could you tell me if I’m just doing something wrong (hopefully it’s
> just that),
> or if SymPy is really unable to perform these operations?
>
> Thanks. : - )
>
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