NAME

chptri - compute the inverse of a complex Hermitian indefinite matrix A in packed storage using the factorization A = U∗D∗U∗∗H or A = L∗D∗L∗∗H computed by CHPTRF

SYNOPSIS

SUBROUTINE CHPTRI( UPLO, N, AP, IPIV, WORK, INFO )

CHARACTER UPLO

INTEGER INFO, N

INTEGER IPIV( ∗ )

COMPLEX AP( ∗ ), WORK( ∗ )

#include <sunperf.h>

void chptri(char uplo, int n, complex ∗cap, int ∗ipivot, int ∗info) ;

PURPOSE

CHPTRI computes the inverse of a complex Hermitian indefinite matrix A in packed storage using the factorization A = U∗D∗U∗∗H or A = L∗D∗L∗∗H computed by CHPTRF. 
 

ARGUMENTS

UPLO (input) CHARACTER∗1
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∗∗H;
= ’L’:  Lower triangular, form is A = L∗D∗L∗∗H.

N (input) INTEGER
The order of the matrix A.  N >= 0.

AP (input/output) COMPLEX array, dimension (N∗(N+1)/2)
On entry, the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by CHPTRF, stored as a packed triangular matrix.
 
On exit, if INFO = 0, the (Hermitian) inverse of the original matrix, stored as a packed triangular matrix. The j-th column of inv(A) is stored in the array AP as follows: if UPLO = ’U’, AP(i + (j-1)∗j/2) = inv(A)(i,j) for 1<=i<=j; if UPLO = ’L’, AP(i + (j-1)∗(2n-j)/2) = inv(A)(i,j) for j<=i<=n.

IPIV (input) INTEGER array, dimension (N)
Details of the interchanges and the block structure of D as determined by CHPTRF.

WORK (workspace) COMPLEX array, dimension (N)

INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, D(i,i) = 0; the matrix is singular and its inverse could not be computed.

SunOS 5.0  —  Last change: 10 Dec 1998