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