Contents
zsytri - compute the inverse of a complex symmetric indefin-
ite matrix A using the factorization A = U*D*U**T or A =
L*D*L**T computed by ZSYTRF
SUBROUTINE ZSYTRI(UPLO, N, A, LDA, IPIVOT, WORK, INFO)
CHARACTER * 1 UPLO
DOUBLE COMPLEX A(LDA,*), WORK(*)
INTEGER N, LDA, INFO
INTEGER IPIVOT(*)
SUBROUTINE ZSYTRI_64(UPLO, N, A, LDA, IPIVOT, WORK, INFO)
CHARACTER * 1 UPLO
DOUBLE COMPLEX A(LDA,*), WORK(*)
INTEGER*8 N, LDA, INFO
INTEGER*8 IPIVOT(*)
F95 INTERFACE
SUBROUTINE SYTRI(UPLO, N, A, [LDA], IPIVOT, [WORK], [INFO])
CHARACTER(LEN=1) :: UPLO
COMPLEX(8), DIMENSION(:) :: WORK
COMPLEX(8), DIMENSION(:,:) :: A
INTEGER :: N, LDA, INFO
INTEGER, DIMENSION(:) :: IPIVOT
SUBROUTINE SYTRI_64(UPLO, N, A, [LDA], IPIVOT, [WORK], [INFO])
CHARACTER(LEN=1) :: UPLO
COMPLEX(8), DIMENSION(:) :: WORK
COMPLEX(8), DIMENSION(:,:) :: A
INTEGER(8) :: N, LDA, INFO
INTEGER(8), DIMENSION(:) :: IPIVOT
C INTERFACE
#include <sunperf.h>
void zsytri(char uplo, int n, doublecomplex *a, int lda, int
*ipivot, int *info);
void zsytri_64(char uplo, long n, doublecomplex *a, long
lda, long *ipivot, long *info);
zsytri computes the inverse of a complex symmetric indefin-
ite matrix A using the factorization A = U*D*U**T or A =
L*D*L**T computed by ZSYTRF.
UPLO (input)
Specifies whether the details of the factorization
are stored as an upper or lower triangular matrix.
= 'U': Upper triangular, form is A = U*D*U**T;
= 'L': Lower triangular, form is A = L*D*L**T.
N (input) The order of the matrix A. N >= 0.
A (input/output)
On entry, the block diagonal matrix D and the mul-
tipliers used to obtain the factor U or L as com-
puted by ZSYTRF.
On exit, if INFO = 0, the (symmetric) inverse of
the original matrix. If UPLO = 'U', the upper
triangular part of the inverse is formed and the
part of A below the diagonal is not referenced; if
UPLO = 'L' the lower triangular part of the
inverse is formed and the part of A above the
diagonal is not referenced.
LDA (input)
The leading dimension of the array A. LDA >=
max(1,N).
IPIVOT (input)
Details of the interchanges and the block struc-
ture of D as determined by ZSYTRF.
WORK (workspace)
dimension(2*N)
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal value
> 0: if INFO = i, D(i,i) = 0; the matrix is singu-
lar and its inverse could not be computed.