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172. EIGEN: Eigenvalue and Eigenvector by Modified
Nesbet Method
by Isaiah Shavitt, Battelle Memorial Institute, Columbus, Ohio 43201 The subroutine EIGEN computes an eigenvalue (usually the lowest) and corresponding eigenvector of a real symmetric matrix. The matrix need not fit into the central memory, and only the non-zero elements (ordered by row for the lower triangle and suitably identified) need to be provided. The user must supply a subroutine ROW to access the matrix, one row at a time. The method is iterative, and an initial guess for the desired eigenvector must be provided. FORTRAN IV Lines of Code: 387 Recommended Citation: I. Shavitt, QCPE 11, 172 (1970). |