?syconv

Converts a symmetric matrix given by a triangular matrix factorization into two matrices and vice versa.

Syntax

FORTRAN 77:

call ssyconv( uplo, way, n, a, lda, ipiv, work, info )

call dsyconv( uplo, way, n, a, lda, ipiv, work, info )

call csyconv( uplo, way, n, a, lda, ipiv, work, info )

call zsyconv( uplo, way, n, a, lda, ipiv, work, info )

FORTRAN 95:

call sycon( a[,uplo][,way][,ipiv][,info] )

Include Files

Fortran: mkl_lapack.fi and mkl_lapack.h
Fortran 95: lapack.f90
C: mkl_lapacke.h

Description

The routine converts matrix A, which results from a triangular matrix factorization, into matrices L and D and vice versa. The routine gets non-diagonalized elements of D returned in the workspace and applies or reverses permutation done with the triangular matrix factorization.

Input Parameters

uplo	CHARACTER1. Must be 'U' or 'L'. Indicates whether the details of the factorization are stored as an upper or lower triangular matrix: If `uplo = 'U'`: the upper triangular, `A = UDU^T`. If `uplo = 'L'`: the lower triangular, `A = LD*L^T`.
way	CHARACTER*1. Must be 'C' or 'R'. Indicates whether the routine converts or reverts the matrix: `way = 'C'` means conversion. `way = 'R'` means reversion.
n	INTEGER. The order of matrix `A`; `n` ≥ 0.
a	REAL for ssyconv DOUBLE PRECISION for dsyconv COMPLEX for csyconv DOUBLE COMPLEX for zsyconv Array of DIMENSION (`lda`,`n`). The block diagonal matrix `D` and the multipliers used to obtain the factor U or L as computed by ?sytrf.
lda	INTEGER. The leading dimension of `a`; `lda ≥ max(1, n)`.
ipiv	INTEGER. Array, DIMENSION at least `max(1, n)`. Details of the interchanges and the block structure of `D`, as returned by ?sytrf.
work	INTEGER. Workspace array, DIMENSION at least `max(1, n)`.

Output Parameters

info	INTEGER. If `info = 0`, the execution is successful. If `info` < 0, the `i`-th parameter had an illegal value.

Fortran 95 Interface Notes

Routines in Fortran 95 interface have fewer arguments in the calling sequence than their FORTRAN 77 counterparts. For general conventions applied to skip redundant or reconstructible arguments, see Fortran 95 Interface Conventions.

Specific details for the routine syconv interface are as follows:

a	Holds the matrix `A` of size (`n`, `n`).
uplo	Must be 'U' or 'L'.
way	Must be 'C' or 'R'.
ipiv	Holds the vector of length `n`.