stevx#

Functions

void sstevx(
    const char*          jobz,
    const char*          range,
    const INT            n,
          f32*  restrict D,
          f32*  restrict E,
    const f32            vl,
    const f32            vu,
    const INT            il,
    const INT            iu,
    const f32            abstol,
          INT*           m,
          f32*  restrict W,
          f32*  restrict Z,
    const INT            ldz,
          f32*  restrict work,
          INT*  restrict iwork,
          INT*  restrict ifail,
          INT*           info
);
void sstevx(const char *jobz, const char *range, const INT n, f32 *restrict D, f32 *restrict E, const f32 vl, const f32 vu, const INT il, const INT iu, const f32 abstol, INT *m, f32 *restrict W, f32 *restrict Z, const INT ldz, f32 *restrict work, INT *restrict iwork, INT *restrict ifail, INT *info)#

SSTEVX computes selected eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix A.

Eigenvalues and eigenvectors can be selected by specifying either a range of values or a range of indices for the desired eigenvalues.

Parameters

in
jobz

= ‘N’: Compute eigenvalues only; = ‘V’: Compute eigenvalues and eigenvectors.

in
range

= ‘A’: all eigenvalues will be found. = ‘V’: all eigenvalues in the half-open interval (vl, vu] will be found. = ‘I’: the il-th through iu-th eigenvalues will be found.

in
n

The order of the matrix. n >= 0.

inout
D

Double precision array, dimension (n). On entry, the n diagonal elements of the tridiagonal matrix A. On exit, D may be multiplied by a constant factor chosen to avoid over/underflow.

inout
E

Double precision array, dimension (max(1,n-1)). On entry, the (n-1) subdiagonal elements. On exit, E may be multiplied by a constant factor.

in
vl

If range=’V’, the lower bound of the interval.

in
vu

If range=’V’, the upper bound of the interval.

in
il

If range=’I’, the index of the smallest eigenvalue to be returned (0-based).

in
iu

If range=’I’, the index of the largest eigenvalue to be returned (0-based).

in
abstol

The absolute error tolerance for the eigenvalues.

out
m

The total number of eigenvalues found.

out
W

Double precision array, dimension (n). The first m elements contain the selected eigenvalues in ascending order.

out
Z

Double precision array, dimension (ldz, max(1,m)). If jobz=’V’, the first m columns contain the orthonormal eigenvectors.

in
ldz

The leading dimension of Z. ldz >= 1, and if jobz=’V’, ldz >= max(1,n).

out
work

Double precision array, dimension (5*n).

out
iwork

Integer array, dimension (5*n).

out
ifail

Integer array, dimension (n). If jobz=’V’, on normal exit all elements are zero. If info > 0, contains indices of eigenvectors that failed to converge.

out
info

  • = 0: successful exit

  • < 0: if info = -i, the i-th argument had an illegal value

  • > 0: if info = i, then i eigenvectors failed to converge.

Functions

void dstevx(
    const char*          jobz,
    const char*          range,
    const INT            n,
          f64*  restrict D,
          f64*  restrict E,
    const f64            vl,
    const f64            vu,
    const INT            il,
    const INT            iu,
    const f64            abstol,
          INT*           m,
          f64*  restrict W,
          f64*  restrict Z,
    const INT            ldz,
          f64*  restrict work,
          INT*  restrict iwork,
          INT*  restrict ifail,
          INT*           info
);
void dstevx(const char *jobz, const char *range, const INT n, f64 *restrict D, f64 *restrict E, const f64 vl, const f64 vu, const INT il, const INT iu, const f64 abstol, INT *m, f64 *restrict W, f64 *restrict Z, const INT ldz, f64 *restrict work, INT *restrict iwork, INT *restrict ifail, INT *info)#

DSTEVX computes selected eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix A.

Eigenvalues and eigenvectors can be selected by specifying either a range of values or a range of indices for the desired eigenvalues.

Parameters

in
jobz

= ‘N’: Compute eigenvalues only; = ‘V’: Compute eigenvalues and eigenvectors.

in
range

= ‘A’: all eigenvalues will be found. = ‘V’: all eigenvalues in the half-open interval (vl, vu] will be found. = ‘I’: the il-th through iu-th eigenvalues will be found.

in
n

The order of the matrix. n >= 0.

inout
D

Double precision array, dimension (n). On entry, the n diagonal elements of the tridiagonal matrix A. On exit, D may be multiplied by a constant factor chosen to avoid over/underflow.

inout
E

Double precision array, dimension (max(1,n-1)). On entry, the (n-1) subdiagonal elements. On exit, E may be multiplied by a constant factor.

in
vl

If range=’V’, the lower bound of the interval.

in
vu

If range=’V’, the upper bound of the interval.

in
il

If range=’I’, the index of the smallest eigenvalue to be returned (0-based).

in
iu

If range=’I’, the index of the largest eigenvalue to be returned (0-based).

in
abstol

The absolute error tolerance for the eigenvalues.

out
m

The total number of eigenvalues found.

out
W

Double precision array, dimension (n). The first m elements contain the selected eigenvalues in ascending order.

out
Z

Double precision array, dimension (ldz, max(1,m)). If jobz=’V’, the first m columns contain the orthonormal eigenvectors.

in
ldz

The leading dimension of Z. ldz >= 1, and if jobz=’V’, ldz >= max(1,n).

out
work

Double precision array, dimension (5*n).

out
iwork

Integer array, dimension (5*n).

out
ifail

Integer array, dimension (n). If jobz=’V’, on normal exit all elements are zero. If info > 0, contains indices of eigenvectors that failed to converge.

out
info

  • = 0: successful exit

  • < 0: if info = -i, the i-th argument had an illegal value

  • > 0: if info = i, then i eigenvectors failed to converge.

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