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Re: Re: Eigenvalues broken?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg102866] Re: [mg102837] Re: [mg102827] Eigenvalues broken?
  • From: John Fultz <jfultz at wolfram.com>
  • Date: Mon, 31 Aug 2009 06:35:10 -0400 (EDT)
  • Reply-to: jfultz at wolfram.com

I have not a whit to contribute to the issue of whether or how this is
broken (too far off from my own field of expertise).  But I thought you
might like to know that it's easy enough to run the 32-bit version from
your 64-bit install.

You can use the Evaluation->Kernel Configuration Options... dialog to
tailor the existing kernel or create a new one to be launched as...

SystemFiles\Kernel\Binaries\Windows\MathKernel

Sincerely,
 
John Fultz
jfultz at wolfram.com
User Interface Group
Wolfram Research, Inc.


On Sat, 29 Aug 2009 06:30:35 -0400 (EDT), Vadim Oganesyan wrote:
> Windows XP Pro x64
>
> Interestingly, 32 bit laptop executes this code flawlessly.
>
>
> On Fri, Aug 28, 2009 at 9:47 AM, Sseziwa Mukasa <mukasa at jeol.com> wrote:
>
>> On Aug 28, 2009, at 12:47 AM, vadim.oganesyan at gmail.com wrote:
>>
>> I have been doing full diagonalization of sparse symmetric real
>>> matrices (Hamiltonians) of different sizes and just noticed that
>>> Eigenvalues (and Eigensystem) break once the matrices are 256by256
>>> (maybe smaller, but that's where i first saw it).
>>>
>>> i first noticed the problem when checking the quality of the solutions
>>> by comparing eigenvalues with expectation of the matrix in each of
>>> eigenvectors.
>>>
>>> even more dramatically, simply rerunning Eigenvalues twice on the same
>>> matrix produces somewhat different results!!!
>>>
>>> If I chose to get only few eigenvales (thus forcing it to use Arnoldi
>>> method) the problem goes away.
>>>
>>> I was recently told that the version of Lapack used by Mathemica was
>>> recompiled by people at Wolfram for added functionality -- did they
>>> break it too?
>>> My trusty C++ code has no problems with these matrices....
>>>
>>> thoughts? suggestions?
>>>
>>
>> What platform are you using?  I've had problems with the numeric linear
>> algebra routines on OS X, the same code seems to work on Windows.
>>
>> Regards,
>>
>> Sseziwa





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