Reported by Sylvestre Ledru, Feb 21, 2012
reported by Tim Mitchell - When rvec = .false., the Ritz values are outputted according to their dsortc() order - When rvec = .true., the eigenvectors also need to be rearranged so dneupd() calls dtrsen() from LAPACK to reorder both the Ritz values and their associated vectors - Unfortunately, dtrsen() only uses a boolean select array to do the regrouping; it is not written to take advantage of any ordering info - The easiest fix might be to create a modified dtrsen which can use an ordering (which is already computed previously in dneupd)
Comment 1 by Danie Ludick, May 14, 2014
Good day, I also get this issue, i.e., that when rvec=.true. the Ritz values are not sorted - even though I am specifying 'LM' as the ordering parameter. Is there any updates / progress regarding the modified version of dtrsen() - or perhaps any other suggestion. For reference, I have attached a file containing the Ritz values and relative residuals I get when solving a 4248 x 4248 double precision eigenproblem.
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