LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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subroutine sspev | ( | character | jobz, |
character | uplo, | ||
integer | n, | ||
real, dimension( * ) | ap, | ||
real, dimension( * ) | w, | ||
real, dimension( ldz, * ) | z, | ||
integer | ldz, | ||
real, dimension( * ) | work, | ||
integer | info | ||
) |
SSPEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices
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SSPEV computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage.
[in] | JOBZ | JOBZ is CHARACTER*1 = 'N': Compute eigenvalues only; = 'V': Compute eigenvalues and eigenvectors. |
[in] | UPLO | UPLO is CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored. |
[in] | N | N is INTEGER The order of the matrix A. N >= 0. |
[in,out] | AP | AP is REAL array, dimension (N*(N+1)/2) On entry, the upper or lower triangle of the symmetric matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2*n-j)/2) = A(i,j) for j<=i<=n. On exit, AP is overwritten by values generated during the reduction to tridiagonal form. If UPLO = 'U', the diagonal and first superdiagonal of the tridiagonal matrix T overwrite the corresponding elements of A, and if UPLO = 'L', the diagonal and first subdiagonal of T overwrite the corresponding elements of A. |
[out] | W | W is REAL array, dimension (N) If INFO = 0, the eigenvalues in ascending order. |
[out] | Z | Z is REAL array, dimension (LDZ, N) If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal eigenvectors of the matrix A, with the i-th column of Z holding the eigenvector associated with W(i). If JOBZ = 'N', then Z is not referenced. |
[in] | LDZ | LDZ is INTEGER The leading dimension of the array Z. LDZ >= 1, and if JOBZ = 'V', LDZ >= max(1,N). |
[out] | WORK | WORK is REAL array, dimension (3*N) |
[out] | INFO | INFO is INTEGER = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value. > 0: if INFO = i, the algorithm failed to converge; i off-diagonal elements of an intermediate tridiagonal form did not converge to zero. |
Definition at line 129 of file sspev.f.