Re: Re: Eigenvalues
- To: mathgroup@smc.vnet.net
- Subject: [mg11571] Re: [mg11489] Re: [mg11476] Eigenvalues
- From: Daniel Lichtblau <danl@wolfram.com>
- Date: Tue, 17 Mar 1998 10:42:55 -0500
- References: <199803120635.BAA23688@smc.vnet.net.> <199803131721.MAA03635@smc.vnet.net.>
Daniel Lichtblau wrote:
>
> Raya Khanin wrote:
> >
> > Hi,
> >
> > I have a problem of calculating eigenvalues for a simple 4X4 matrix. I
> > am working on Sun workstation, and it takes minutes and minutes for
> > Mathematica to perform Eigenvalues[] operation for a matrix like this
> >
> > Clear[a, b, c, d, e, d, f, g];
> > testmatrix = {{a, b, c, d}, {b, c, d, e}, {c, d, e, f}, {d, e, f, g}};
> > Eigenvalues[testmatrix];
> >
>
> I get a huge result quite quickly. To improve on the size, try
>
> In[72]:= testmatrix = {{a, b, c, d}, {b, c, d, e},
> {c, d, e, f}, {d, e, f, g}};
>
> In[73]:= Timing[ev = Eigenvalues[testmatrix];] Out[73]= {0.83 Second,
> Null}
>
> In[74]:= LeafCount[ev]
> Out[74]= 1449
> ...
> Daniel Lichtblau
> Wolfram Research
Sorry, I missed an important line in the cut-and-paste.
First do
SetOptions[Roots, Quartics->False]
This is because Eigenvalues will, in the symbolic case, compute and call
Roots on the characteristic polynomial.
(Still Daniel Lichtblau at WRI)
- References:
- Eigenvalues
- From: Raya Khanin <raya@maths.ed.ac.uk>
- Re: Eigenvalues
- From: Daniel Lichtblau <danl@wolfram.com>
- Eigenvalues