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### [Lapack] Enquiry.

 ```Dear J. J. Dongarra, May I ask a favor from you, please? I have been trying to obtain the eigenvalues and eigenvectors of a symmetric tridiagonal matrix using CLAPACK rountines (dstegr_, dstevr_, dstevx_, dsterf_, dsyevr_ dsyevd_) on a Dell Pentium 4 PC that operates in Vine Linux 3.1. The eigenvalues that I obtained from all these routines are the same, that is, E1 = -536 meV, E2 = 57 meV, and E3 =185 meV. The correct values are approximately E1 = 30 meV, E2 = 112 meV and E3 = 188 meV. I have checked the diagonal elements and sub- and super diagonal elements that I passed to dstegr_, dstevr_, dstevx_, and dsterf_ by constructing the symmetric tridiagonal matrix and solve for the eigenvalues and eigenvectors using Igor Pro 4.01A. Correct eigenvalues and eigenvectors were obtained using Igor Pro 4.01A that uses LAPACK routines. Unfortunately, the LAPACK routines that Igor Pro 4.01A uses to calculate the eigenvalues and eigenvectors of the matrix were not known. I have checked the matrix passed to dsyevr_ dsyevd_() by using Igor Pro 4.01A to calculate the eigenvalues and vectors of this matrix, and correct eigenvalues and eigenvectors were obtained. I have also tried dgeevx_ but I got E1 = nan meV, E2 = nan meV, and E3 = nan meV. The value of INFO passed back from CLAPACK routines is 0 for all the above CLAPACK routines that I have tried. May I have your valuable advice on how could I obtain the correct eigenvalues and eigenvectors using CLAPACK on Linux, please? I have attached the 400x400 matrix (i.e., C.dat), its diagonal elements (i.e., B.dat) and sub-/super-diagonal elements (i.e., A.dat), source files as well as the 400x400 matrix (i.e., Matrix.dat) that Igor Pro 4.01A solves to this e-mail. Thank you very much for your kind attention, and I look forward earnestly to your valuable advice. Yours sincerely, Cheng -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/attachment-0001.html -------------- next part -------------- A non-text attachment was scrubbed... Name: EigenValues_dsterf_.c Type: application/octet-stream Size: 2101 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/EigenValues_dsterf_-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: EigenVector_dgeevx_.c Type: application/octet-stream Size: 11605 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/EigenVector_dgeevx_-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: EigenVector_dstegr_.c Type: application/octet-stream Size: 3741 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/EigenVector_dstegr_-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: EigenVector_dstevr_.c Type: application/octet-stream Size: 3741 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/EigenVector_dstevr_-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: EigenVector_dstevx_.c Type: application/octet-stream Size: 3665 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/EigenVector_dstevx_-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: EigenVector_dsyevd_.c Type: application/octet-stream Size: 11440 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/EigenVector_dsyevd_-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: EigenVector_dsyevr_.c Type: application/octet-stream Size: 12072 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/EigenVector_dsyevr_-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: Matrix.dat Type: application/octet-stream Size: 331883 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/Matrix-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: A.dat Type: application/octet-stream Size: 8379 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/A-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: B.dat Type: application/octet-stream Size: 7980 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/B-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: C.dat Type: application/octet-stream Size: 4320798 bytes Desc: not available Url : http://lists.cs.utk.edu/private/lapack/attachments/20071115/e873d2bd/C-0001.obj ```
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