       arnoldi method with Mathematica

• To: mathgroup at smc.vnet.net
• Subject: [mg45951] arnoldi method with Mathematica
• From: hweekuan at yahoo.com (Hwee Kuan)
• Date: Fri, 30 Jan 2004 04:16:57 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

I am using Mathematica v5 for computation of large non-symmetric
tridiagonal matrices. I am trying to use the Eigenvalues[] function
with Arnoldi method, however, I got the following errors:

Eigenvalues::arm:
Method->Arnoldi can only be used for matrices of machine numbers.

Does anyone know how to get around this error? I needed precision
higher than the machine precision. Thank you in advance for the help.

*** A simple example of my code is given below.

(* this is ok, but please see below *)
In:= sp = SparseArray[N[{{1,2,3},{3,2,1},{1,1,1}}]]

Out= SparseArray[<9>, {3, 3}]

In:= Eigenvalues[sp,1,Method->Arnoldi]

Out= {5.}     <--- gives answer without error, but....if I specify
precision using SetPrecision I get error messages.

In:= \$MinPrecision = 20 \$MachinePrecision

Out= 319.092

In:= spm = SetPrecision[ SparseArray[N[{{1,2,3},{3,2,1},{1,1,1}}]],
\$MinPrecision]

Out= SparseArray[<9>, {3, 3}]

In:=  Eigenvalues[spm,1,Method->Arnoldi]

Eigenvalues::arm:
Method->Arnoldi can only be used for matrices of machine numbers.

```

• Prev by Date: Re: Creating New Symbols
• Next by Date: Re: unpartition
• Previous by thread: Help with "recession bar" graph
• Next by thread: Simplifying a second order eq. system tests=PRIORITY_NO_NAME version=2.55