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template<typename T>
void spev(char *jobz, char *uplo, integer *n, T *ap, T *w, T *z, integer *ldq, T *work, integer *info)# SSPEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices.
Purpose:
SSPEV computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage.
- Parameters:
JOBZ – [in]
JOBZ is CHARACTER*1
= ‘N’: Compute eigenvalues only;
= ‘V’: Compute eigenvalues and eigenvectors.UPLO – [in]
UPLO is CHARACTER*1
= ‘U’: Upper triangle of A is stored;
= ‘L’: Lower triangle of A is stored.N – [in]
N is INTEGER
The order of the matrix A. N >= 0.
AP – [inout]
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.W – [out]
W is REAL array, dimension (N)
If INFO = 0, the eigenvalues in ascending order.
Z – [out]
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.LDZ – [in]
LDZ is INTEGER
The leading dimension of the array Z. LDZ >= 1, and if JOBZ = ‘V’, LDZ >= fla_max(1,N).
WORK – [out] WORK is REAL array, dimension (3*N)
INFO – [out]
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.