NAME

SYNOPSIS

  SUBROUTINE ZSYTF2( UPLO, N, A, LDA, IPIV, INFO)
  CHARACTER * 1 UPLO
  DOUBLE COMPLEX A(LDA,*)
  INTEGER N, LDA, INFO
  INTEGER IPIV(*)
 
  SUBROUTINE ZSYTF2_64( UPLO, N, A, LDA, IPIV, INFO)
  CHARACTER * 1 UPLO
  DOUBLE COMPLEX A(LDA,*)
  INTEGER*8 N, LDA, INFO
  INTEGER*8 IPIV(*)
 

F95 INTERFACE

  SUBROUTINE SYTF2( UPLO, [N], A, [LDA], IPIV, [INFO])
  CHARACTER(LEN=1) :: UPLO
  COMPLEX(8), DIMENSION(:,:) :: A
  INTEGER :: N, LDA, INFO
  INTEGER, DIMENSION(:) :: IPIV
 
  SUBROUTINE SYTF2_64( UPLO, [N], A, [LDA], IPIV, [INFO])
  CHARACTER(LEN=1) :: UPLO
  COMPLEX(8), DIMENSION(:,:) :: A
  INTEGER(8) :: N, LDA, INFO
  INTEGER(8), DIMENSION(:) :: IPIV
 

C INTERFACE

void zsytf2(char uplo, int n, doublecomplex *a, int lda, int *ipiv, int *info);

void zsytf2_64(char uplo, long n, doublecomplex *a, long lda, long *ipiv, long *info);

PURPOSE

   A = U*D*U'  or  A = L*D*L'

where U (or L) is a product of permutation and unit upper (lower) triangular matrices, U' is the transpose of U, and D is symmetric and block diagonal with 1-by-1 and 2-by-2 diagonal blocks.

This is the unblocked version of the algorithm, calling Level 2 BLAS.

ARGUMENTS

* UPLO (input)

Specifies whether the upper or lower triangular part of the symmetric matrix A is stored:

* N (input)

The order of the matrix A. N >= 0.

* A (input/output)

On entry, the symmetric matrix A. If UPLO = 'U', the leading n-by-n upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading n-by-n lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced.

On exit, the block diagonal matrix D and the multipliers used to obtain the factor U or L (see below for further details).

* LDA (input)

The leading dimension of the array A. LDA >= max(1,N).

* IPIV (output)

Details of the interchanges and the block structure of D. If IPIV(k) > 0, then rows and columns k and IPIV(k) were interchanged and D(k,k) is a 1-by-1 diagonal block. If UPLO = 'U' and IPIV(k) = IPIV(k-1) < 0, then rows and columns k-1 and -IPIV(k) were interchanged and D(k-1:k,k-1:k) is a 2-by-2 diagonal block. If UPLO = 'L' and IPIV(k) = IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were interchanged and D(k:k+1,k:k+1) is a 2-by-2 diagonal block.

* INFO (output)