dspev (l) - Linux Manuals
dspev: computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage
Command to display dspev manual in Linux: $ man l dspev
NAME
DSPEV - computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage
SYNOPSIS
- SUBROUTINE DSPEV(
-
JOBZ, UPLO, N, AP, W, Z, LDZ, WORK, INFO )
-
CHARACTER
JOBZ, UPLO
-
INTEGER
INFO, LDZ, N
-
DOUBLE
PRECISION AP( * ), W( * ), WORK( * ), Z( LDZ, * )
PURPOSE
DSPEV computes all the eigenvalues and, optionally, eigenvectors of a
real symmetric matrix A in packed storage.
ARGUMENTS
- JOBZ (input) CHARACTER*1
-
= aqNaq: Compute eigenvalues only;
= aqVaq: Compute eigenvalues and eigenvectors.
- UPLO (input) CHARACTER*1
-
= aqUaq: Upper triangle of A is stored;
= aqLaq: Lower triangle of A is stored.
- N (input) INTEGER
-
The order of the matrix A. N >= 0.
- AP (input/output) DOUBLE PRECISION 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 = aqUaq, AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
if UPLO = aqLaq, 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 = aqUaq, the diagonal
and first superdiagonal of the tridiagonal matrix T overwrite
the corresponding elements of A, and if UPLO = aqLaq, the
diagonal and first subdiagonal of T overwrite the
corresponding elements of A.
- W (output) DOUBLE PRECISION array, dimension (N)
-
If INFO = 0, the eigenvalues in ascending order.
- Z (output) DOUBLE PRECISION array, dimension (LDZ, N)
-
If JOBZ = aqVaq, 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 = aqNaq, then Z is not referenced.
- LDZ (input) INTEGER
-
The leading dimension of the array Z. LDZ >= 1, and if
JOBZ = aqVaq, LDZ >= max(1,N).
- WORK (workspace) DOUBLE PRECISION array, dimension (3*N)
-
- INFO (output) 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.
Pages related to dspev
- dspev (3)
- dspevd (l) - computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage
- dspevx (l) - computes selected eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage
- dspcon (l) - estimates the reciprocal of the condition number (in the 1-norm) of a real symmetric packed matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by DSPTRF
- dspgst (l) - reduces a real symmetric-definite generalized eigenproblem to standard form, using packed storage
- dspgv (l) - computes all the eigenvalues and, optionally, the eigenvectors of a real generalized symmetric-definite eigenproblem, of the form A*x=(lambda)*B*x, A*Bx=(lambda)*x, or B*A*x=(lambda)*x
- dspgvd (l) - computes all the eigenvalues, and optionally, the eigenvectors of a real generalized symmetric-definite eigenproblem, of the form A*x=(lambda)*B*x, A*Bx=(lambda)*x, or B*A*x=(lambda)*x
- dspgvx (l) - computes selected eigenvalues, and optionally, eigenvectors of a real generalized symmetric-definite eigenproblem, of the form A*x=(lambda)*B*x, A*Bx=(lambda)*x, or B*A*x=(lambda)*x
- dspmv (l) - performs the matrix-vector operation y := alpha*A*x + beta*y,