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## Re: Issues with eigs

 From: Doug Stewart Subject: Re: Issues with eigs Date: Fri, 7 Sep 2018 13:31:57 -0400

On Fri, Sep 7, 2018 at 12:14 PM Thomas D. Dean <address@hidden> wrote:
I get different results with 5.0.0

octave:627> eigs(m1,m0)
ans =

-0.00018 - 2672287.08391i
-0.00018 + 2672287.08391i
0.00027 + 2639894.41870i
0.00027 - 2639894.41870i
-0.00024 - 2587680.34565i
-0.00024 + 2587680.34565i

octave:628> version
ans = 5.0.0
octave:629> which eigs
'eigs' is a function from the file
/usr/local/share/octave/5.0.0/m/sparse/eigs.m

Tom Dean

On 09/07/18 06:13, Juan Pablo Carbajal wrote:
> Hi,
>
> I can't reproduce in 4.4.0, which Octave version are you using? What OS?
>
>> eigs(m1,m0)
> ans =
>
>           0.00032 - 2672312.38464i
>           0.00032 + 2672312.38464i
>           0.00004 - 2639857.10699i
>           0.00004 + 2639857.10699i
>           0.00010 + 2587664.34543i
>           0.00010 - 2587664.34543i
>
>> version
> ans = 4.4.0
>> which eigs
> 'eigs' is a function from the file /usr/local/share/octave/4.4.0/m/sparse/eigs.m
>
> On Fri, Sep 7, 2018 at 3:02 PM Manav Bhatia <address@hidden> wrote:
>>
>> Hi,
>>
>>     I have a set of matrices, M0 and M1 (attached), obtained from numerical discretization of a beam problem.
>>
>>     I am attempting to solve the eigenproblem    M1 x = lambda M0 x .
>>
>>     Computing this with the following works fine:
>>>   eig( m1, m0)
>>
>>
>>      However, using eigs( m1, m0) throws the following error:
>> error: __eigs__: eigs: error -8 in dnaupd
>> error: called from
>>      eigs at line 285 column 18
>>
>>      I am not sure what could be causing this. Any guidance will be appreciated.
>>
>> Thanks,
>> Manav
>>
>>
>
>

and I get
ans =

-0.000005679 + 2672294.228794384i
-0.000005679 - 2672294.228794384i
0.000033536 + 2639901.383827801i
0.000033536 - 2639901.383827801i
-0.000042158 - 2587660.262760939i
-0.000042158 + 2587660.262760939i
>> version
ans = 4.4.1-rc2
>> which eigs
'eigs' is a function from the file /usr/local/share/octave/4.4.1-rc2/m/sparse/eigs.m
>>
--
DAS