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203 lines
5.8 KiB
203 lines
5.8 KiB
2 years ago
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*> \brief \b ZHETRI2
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*
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* =========== DOCUMENTATION ===========
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*
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* Online html documentation available at
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* http://www.netlib.org/lapack/explore-html/
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*
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*> \htmlonly
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*> Download ZHETRI2 + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zhetri2.f">
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*> [TGZ]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zhetri2.f">
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*> [ZIP]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zhetri2.f">
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*> [TXT]</a>
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*> \endhtmlonly
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*
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* Definition:
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* ===========
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*
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* SUBROUTINE ZHETRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO )
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*
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* .. Scalar Arguments ..
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* CHARACTER UPLO
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* INTEGER INFO, LDA, LWORK, N
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* ..
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* .. Array Arguments ..
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* INTEGER IPIV( * )
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* COMPLEX*16 A( LDA, * ), WORK( * )
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* ..
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*
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*
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*> \par Purpose:
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* =============
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*>
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*> \verbatim
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*>
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*> ZHETRI2 computes the inverse of a COMPLEX*16 hermitian indefinite matrix
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*> A using the factorization A = U*D*U**T or A = L*D*L**T computed by
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*> ZHETRF. ZHETRI2 set the LEADING DIMENSION of the workspace
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*> before calling ZHETRI2X that actually computes the inverse.
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*> \endverbatim
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*
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* Arguments:
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* ==========
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*
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*> \param[in] UPLO
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*> \verbatim
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*> UPLO is CHARACTER*1
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*> Specifies whether the details of the factorization are stored
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*> as an upper or lower triangular matrix.
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*> = 'U': Upper triangular, form is A = U*D*U**T;
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*> = 'L': Lower triangular, form is A = L*D*L**T.
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*> \endverbatim
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*>
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*> \param[in] N
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*> \verbatim
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*> N is INTEGER
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*> The order of the matrix A. N >= 0.
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*> \endverbatim
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*>
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*> \param[in,out] A
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*> \verbatim
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*> A is COMPLEX*16 array, dimension (LDA,N)
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*> On entry, the block diagonal matrix D and the multipliers
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*> used to obtain the factor U or L as computed by ZHETRF.
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*>
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*> On exit, if INFO = 0, the (symmetric) inverse of the original
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*> matrix. If UPLO = 'U', the upper triangular part of the
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*> inverse is formed and the part of A below the diagonal is not
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*> referenced; if UPLO = 'L' the lower triangular part of the
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*> inverse is formed and the part of A above the diagonal is
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*> not referenced.
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*> \endverbatim
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*>
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*> \param[in] LDA
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*> \verbatim
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*> LDA is INTEGER
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*> The leading dimension of the array A. LDA >= max(1,N).
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*> \endverbatim
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*>
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*> \param[in] IPIV
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*> \verbatim
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*> IPIV is INTEGER array, dimension (N)
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*> Details of the interchanges and the block structure of D
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*> as determined by ZHETRF.
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*> \endverbatim
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*>
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*> \param[out] WORK
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*> \verbatim
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*> WORK is COMPLEX*16 array, dimension (N+NB+1)*(NB+3)
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*> \endverbatim
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*>
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*> \param[in] LWORK
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*> \verbatim
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*> LWORK is INTEGER
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*> The dimension of the array WORK.
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*> WORK is size >= (N+NB+1)*(NB+3)
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*> If LWORK = -1, then a workspace query is assumed; the routine
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*> calculates:
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*> - the optimal size of the WORK array, returns
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*> this value as the first entry of the WORK array,
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*> - and no error message related to LWORK is issued by XERBLA.
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*> \endverbatim
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*>
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*> \param[out] INFO
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*> \verbatim
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*> INFO is INTEGER
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*> = 0: successful exit
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*> < 0: if INFO = -i, the i-th argument had an illegal value
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*> > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its
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*> inverse could not be computed.
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*> \endverbatim
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*
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* Authors:
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* ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*
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*> \ingroup complex16HEcomputational
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*
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* =====================================================================
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SUBROUTINE ZHETRI2( UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO )
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*
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* -- LAPACK computational routine --
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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*
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* .. Scalar Arguments ..
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CHARACTER UPLO
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INTEGER INFO, LDA, LWORK, N
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* ..
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* .. Array Arguments ..
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INTEGER IPIV( * )
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COMPLEX*16 A( LDA, * ), WORK( * )
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* ..
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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LOGICAL UPPER, LQUERY
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INTEGER MINSIZE, NBMAX
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* ..
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* .. External Functions ..
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LOGICAL LSAME
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INTEGER ILAENV
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EXTERNAL LSAME, ILAENV
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* ..
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* .. External Subroutines ..
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EXTERNAL ZHETRI2X, ZHETRI, XERBLA
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* ..
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* .. Executable Statements ..
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*
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* Test the input parameters.
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*
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INFO = 0
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UPPER = LSAME( UPLO, 'U' )
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LQUERY = ( LWORK.EQ.-1 )
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* Get blocksize
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NBMAX = ILAENV( 1, 'ZHETRF', UPLO, N, -1, -1, -1 )
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IF ( NBMAX .GE. N ) THEN
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MINSIZE = N
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ELSE
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MINSIZE = (N+NBMAX+1)*(NBMAX+3)
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END IF
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*
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IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
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INFO = -1
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ELSE IF( N.LT.0 ) THEN
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INFO = -2
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ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
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INFO = -4
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ELSE IF (LWORK .LT. MINSIZE .AND. .NOT.LQUERY ) THEN
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INFO = -7
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END IF
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*
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* Quick return if possible
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*
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*
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IF( INFO.NE.0 ) THEN
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CALL XERBLA( 'ZHETRI2', -INFO )
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RETURN
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ELSE IF( LQUERY ) THEN
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WORK(1)=MINSIZE
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RETURN
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END IF
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IF( N.EQ.0 )
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$ RETURN
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IF( NBMAX .GE. N ) THEN
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CALL ZHETRI( UPLO, N, A, LDA, IPIV, WORK, INFO )
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ELSE
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CALL ZHETRI2X( UPLO, N, A, LDA, IPIV, WORK, NBMAX, INFO )
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END IF
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RETURN
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*
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* End of ZHETRI2
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*
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END
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