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SUBROUTINE ZHETRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO )
*
* -- LAPACK routine (version 3.3.0) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2010
*
* -- Written by Julie Langou of the Univ. of TN --
*
* @precisions normal z -> c
*
* .. Scalar Arguments ..
CHARACTER UPLO
INTEGER INFO, LDA, LWORK, N
* ..
* .. Array Arguments ..
INTEGER IPIV( * )
COMPLEX*16 A( LDA, * ), WORK( * )
* ..
*
* Purpose
* =======
*
* ZHETRI2 computes the inverse of a COMPLEX*16 hermitian indefinite matrix
* A using the factorization A = U*D*U**T or A = L*D*L**T computed by
* ZHETRF. ZHETRI2 set the LEADING DIMENSION of the workspace
* before calling ZHETRI2X that actually computes the inverse.
*
* 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**T;
* = 'L': Lower triangular, form is A = L*D*L**T.
*
* N (input) INTEGER
* The order of the matrix A. N >= 0.
*
* A (input/output) COMPLEX*16 array, dimension (LDA,N)
* On entry, the NB diagonal matrix D and the multipliers
* used to obtain the factor U or L as computed by ZHETRF.
*
* 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) INTEGER
* The leading dimension of the array A. LDA >= max(1,N).
*
* IPIV (input) INTEGER array, dimension (N)
* Details of the interchanges and the NB structure of D
* as determined by ZHETRF.
*
* WORK (workspace) COMPLEX*16 array, dimension (N+NB+1)*(NB+3)
*
* LWORK (input) INTEGER
* The dimension of the array WORK.
* WORK is size >= (N+NB+1)*(NB+3)
* If LDWORK = -1, then a workspace query is assumed; the routine
* calculates:
* - the optimal size of the WORK array, returns
* this value as the first entry of the WORK array,
* - and no error message related to LDWORK is issued by XERBLA.
*
* 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.
*
* =====================================================================
*
* .. Local Scalars ..
LOGICAL UPPER, LQUERY
INTEGER MINSIZE, NBMAX
* ..
* .. External Functions ..
LOGICAL LSAME
INTEGER ILAENV
EXTERNAL LSAME, ILAENV
* ..
* .. External Subroutines ..
EXTERNAL ZHETRI2X
* ..
* .. Executable Statements ..
*
* Test the input parameters.
*
INFO = 0
UPPER = LSAME( UPLO, 'U' )
LQUERY = ( LWORK.EQ.-1 )
* Get blocksize
NBMAX = ILAENV( 1, 'ZHETRF', UPLO, N, -1, -1, -1 )
IF ( NBMAX .GE. N ) THEN
MINSIZE = N
ELSE
MINSIZE = (N+NBMAX+1)*(NBMAX+3)
END IF
*
IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
INFO = -1
ELSE IF( N.LT.0 ) THEN
INFO = -2
ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
INFO = -4
ELSE IF (LWORK .LT. MINSIZE .AND. .NOT.LQUERY ) THEN
INFO = -7
END IF
*
* Quick return if possible
*
*
IF( INFO.NE.0 ) THEN
CALL XERBLA( 'ZHETRI2', -INFO )
RETURN
ELSE IF( LQUERY ) THEN
WORK(1)=MINSIZE
RETURN
END IF
IF( N.EQ.0 )
$ RETURN
IF( NBMAX .GE. N ) THEN
CALL ZHETRI( UPLO, N, A, LDA, IPIV, WORK, INFO )
ELSE
CALL ZHETRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO )
END IF
RETURN
*
* End of ZHETRI2
*
END
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