Re: Eigenvalues broken?
- To: mathgroup at smc.vnet.net
- Subject: [mg102837] Re: [mg102827] Eigenvalues broken?
- From: Vadim Oganesyan <vadim.oganesyan at gmail.com>
- Date: Sat, 29 Aug 2009 06:30:35 -0400 (EDT)
- References: <200907310952.FAA19221@smc.vnet.net> <firstname.lastname@example.org>
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 >