LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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subroutine slarrj | ( | integer | n, |
real, dimension( * ) | d, | ||
real, dimension( * ) | e2, | ||
integer | ifirst, | ||
integer | ilast, | ||
real | rtol, | ||
integer | offset, | ||
real, dimension( * ) | w, | ||
real, dimension( * ) | werr, | ||
real, dimension( * ) | work, | ||
integer, dimension( * ) | iwork, | ||
real | pivmin, | ||
real | spdiam, | ||
integer | info | ||
) |
SLARRJ performs refinement of the initial estimates of the eigenvalues of the matrix T.
Download SLARRJ + dependencies [TGZ] [ZIP] [TXT]
Given the initial eigenvalue approximations of T, SLARRJ does bisection to refine the eigenvalues of T, W( IFIRST-OFFSET ) through W( ILAST-OFFSET ), to more accuracy. Initial guesses for these eigenvalues are input in W, the corresponding estimate of the error in these guesses in WERR. During bisection, intervals [left, right] are maintained by storing their mid-points and semi-widths in the arrays W and WERR respectively.
[in] | N | N is INTEGER The order of the matrix. |
[in] | D | D is REAL array, dimension (N) The N diagonal elements of T. |
[in] | E2 | E2 is REAL array, dimension (N-1) The Squares of the (N-1) subdiagonal elements of T. |
[in] | IFIRST | IFIRST is INTEGER The index of the first eigenvalue to be computed. |
[in] | ILAST | ILAST is INTEGER The index of the last eigenvalue to be computed. |
[in] | RTOL | RTOL is REAL Tolerance for the convergence of the bisection intervals. An interval [LEFT,RIGHT] has converged if RIGHT-LEFT < RTOL*MAX(|LEFT|,|RIGHT|). |
[in] | OFFSET | OFFSET is INTEGER Offset for the arrays W and WERR, i.e., the IFIRST-OFFSET through ILAST-OFFSET elements of these arrays are to be used. |
[in,out] | W | W is REAL array, dimension (N) On input, W( IFIRST-OFFSET ) through W( ILAST-OFFSET ) are estimates of the eigenvalues of L D L^T indexed IFIRST through ILAST. On output, these estimates are refined. |
[in,out] | WERR | WERR is REAL array, dimension (N) On input, WERR( IFIRST-OFFSET ) through WERR( ILAST-OFFSET ) are the errors in the estimates of the corresponding elements in W. On output, these errors are refined. |
[out] | WORK | WORK is REAL array, dimension (2*N) Workspace. |
[out] | IWORK | IWORK is INTEGER array, dimension (2*N) Workspace. |
[in] | PIVMIN | PIVMIN is REAL The minimum pivot in the Sturm sequence for T. |
[in] | SPDIAM | SPDIAM is REAL The spectral diameter of T. |
[out] | INFO | INFO is INTEGER Error flag. |
Definition at line 165 of file slarrj.f.