468 lines
14 KiB
Fortran
468 lines
14 KiB
Fortran
*> \brief \b CHETRF_AA
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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 CHETRF_AA + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/chetrf_aa.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/chetrf_aa.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/chetrf_aa.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 CHETRF_AA( 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 N, LDA, LWORK, INFO
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* ..
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* .. Array Arguments ..
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* INTEGER IPIV( * )
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* COMPLEX A( LDA, * ), WORK( * )
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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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*> CHETRF_AA computes the factorization of a complex hermitian matrix A
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*> using the Aasen's algorithm. The form of the factorization is
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*>
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*> A = U**H*T*U or A = L*T*L**H
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*>
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*> where U (or L) is a product of permutation and unit upper (lower)
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*> triangular matrices, and T is a hermitian tridiagonal matrix.
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*>
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*> This is the blocked version of the algorithm, calling Level 3 BLAS.
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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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*> = 'U': Upper triangle of A is stored;
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*> = 'L': Lower triangle of A is stored.
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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 array, dimension (LDA,N)
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*> On entry, the hermitian matrix A. If UPLO = 'U', the leading
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*> N-by-N upper triangular part of A contains the upper
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*> triangular part of the matrix A, and the strictly lower
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*> triangular part of A is not referenced. If UPLO = 'L', the
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*> leading N-by-N lower triangular part of A contains the lower
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*> triangular part of the matrix A, and the strictly upper
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*> triangular part of A is not referenced.
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*>
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*> On exit, the tridiagonal matrix is stored in the diagonals
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*> and the subdiagonals of A just below (or above) the diagonals,
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*> and L is stored below (or above) the subdiagonals, when UPLO
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*> is 'L' (or 'U').
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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[out] IPIV
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*> \verbatim
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*> IPIV is INTEGER array, dimension (N)
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*> On exit, it contains the details of the interchanges, i.e.,
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*> the row and column k of A were interchanged with the
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*> row and column IPIV(k).
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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 array, dimension (MAX(1,LWORK))
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*> On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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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 length of WORK. LWORK >= 2*N. For optimum performance
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*> LWORK >= N*(1+NB), where NB is the optimal blocksize.
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*>
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*> If LWORK = -1, then a workspace query is assumed; the routine
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*> only calculates the optimal size of the WORK array, returns
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*> this value as the first entry of the WORK array, and no error
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*> 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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*> \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 complexHEcomputational
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*
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* =====================================================================
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SUBROUTINE CHETRF_AA( 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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IMPLICIT NONE
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*
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* .. Scalar Arguments ..
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CHARACTER UPLO
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INTEGER N, LDA, LWORK, INFO
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* ..
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* .. Array Arguments ..
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INTEGER IPIV( * )
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COMPLEX A( LDA, * ), WORK( * )
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* ..
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*
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* =====================================================================
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* .. Parameters ..
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COMPLEX ZERO, ONE
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PARAMETER ( ZERO = (0.0E+0, 0.0E+0), ONE = (1.0E+0, 0.0E+0) )
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*
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* .. Local Scalars ..
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LOGICAL LQUERY, UPPER
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INTEGER J, LWKOPT
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INTEGER NB, MJ, NJ, K1, K2, J1, J2, J3, JB
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COMPLEX ALPHA
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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 CLAHEF_AA, CGEMM, CCOPY, CSWAP, CSCAL, XERBLA
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC REAL, CONJG, MAX
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* ..
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* .. Executable Statements ..
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*
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* Determine the block size
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*
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NB = ILAENV( 1, 'CHETRF_AA', UPLO, N, -1, -1, -1 )
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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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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.( 2*N ) .AND. .NOT.LQUERY ) THEN
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INFO = -7
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END IF
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*
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IF( INFO.EQ.0 ) THEN
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LWKOPT = (NB+1)*N
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WORK( 1 ) = LWKOPT
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END IF
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*
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IF( INFO.NE.0 ) THEN
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CALL XERBLA( 'CHETRF_AA', -INFO )
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RETURN
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ELSE IF( LQUERY ) THEN
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RETURN
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END IF
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*
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* Quick return
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*
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IF ( N.EQ.0 ) THEN
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RETURN
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ENDIF
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IPIV( 1 ) = 1
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IF ( N.EQ.1 ) THEN
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A( 1, 1 ) = REAL( A( 1, 1 ) )
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RETURN
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END IF
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*
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* Adjust block size based on the workspace size
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*
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IF( LWORK.LT.((1+NB)*N) ) THEN
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NB = ( LWORK-N ) / N
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END IF
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*
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IF( UPPER ) THEN
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*
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* .....................................................
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* Factorize A as U**H*D*U using the upper triangle of A
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* .....................................................
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*
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* copy first row A(1, 1:N) into H(1:n) (stored in WORK(1:N))
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*
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CALL CCOPY( N, A( 1, 1 ), LDA, WORK( 1 ), 1 )
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*
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* J is the main loop index, increasing from 1 to N in steps of
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* JB, where JB is the number of columns factorized by CLAHEF;
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* JB is either NB, or N-J+1 for the last block
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*
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J = 0
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10 CONTINUE
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IF( J.GE.N )
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$ GO TO 20
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*
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* each step of the main loop
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* J is the last column of the previous panel
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* J1 is the first column of the current panel
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* K1 identifies if the previous column of the panel has been
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* explicitly stored, e.g., K1=1 for the first panel, and
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* K1=0 for the rest
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*
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J1 = J + 1
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JB = MIN( N-J1+1, NB )
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K1 = MAX(1, J)-J
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*
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* Panel factorization
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*
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CALL CLAHEF_AA( UPLO, 2-K1, N-J, JB,
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$ A( MAX(1, J), J+1 ), LDA,
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$ IPIV( J+1 ), WORK, N, WORK( N*NB+1 ) )
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*
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* Adjust IPIV and apply it back (J-th step picks (J+1)-th pivot)
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*
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DO J2 = J+2, MIN(N, J+JB+1)
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IPIV( J2 ) = IPIV( J2 ) + J
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IF( (J2.NE.IPIV(J2)) .AND. ((J1-K1).GT.2) ) THEN
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CALL CSWAP( J1-K1-2, A( 1, J2 ), 1,
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$ A( 1, IPIV(J2) ), 1 )
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END IF
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END DO
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J = J + JB
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*
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* Trailing submatrix update, where
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* the row A(J1-1, J2-1:N) stores U(J1, J2+1:N) and
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* WORK stores the current block of the auxiriarly matrix H
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*
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IF( J.LT.N ) THEN
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*
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* if the first panel and JB=1 (NB=1), then nothing to do
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*
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IF( J1.GT.1 .OR. JB.GT.1 ) THEN
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*
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* Merge rank-1 update with BLAS-3 update
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*
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ALPHA = CONJG( A( J, J+1 ) )
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A( J, J+1 ) = ONE
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CALL CCOPY( N-J, A( J-1, J+1 ), LDA,
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$ WORK( (J+1-J1+1)+JB*N ), 1 )
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CALL CSCAL( N-J, ALPHA, WORK( (J+1-J1+1)+JB*N ), 1 )
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*
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* K1 identifies if the previous column of the panel has been
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* explicitly stored, e.g., K1=0 and K2=1 for the first panel,
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* and K1=1 and K2=0 for the rest
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*
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IF( J1.GT.1 ) THEN
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*
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* Not first panel
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*
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K2 = 1
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ELSE
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*
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* First panel
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*
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K2 = 0
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*
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* First update skips the first column
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*
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JB = JB - 1
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END IF
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*
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DO J2 = J+1, N, NB
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NJ = MIN( NB, N-J2+1 )
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*
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* Update (J2, J2) diagonal block with CGEMV
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*
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J3 = J2
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DO MJ = NJ-1, 1, -1
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CALL CGEMM( 'Conjugate transpose', 'Transpose',
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$ 1, MJ, JB+1,
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$ -ONE, A( J1-K2, J3 ), LDA,
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$ WORK( (J3-J1+1)+K1*N ), N,
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$ ONE, A( J3, J3 ), LDA )
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J3 = J3 + 1
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END DO
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*
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* Update off-diagonal block of J2-th block row with CGEMM
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*
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CALL CGEMM( 'Conjugate transpose', 'Transpose',
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$ NJ, N-J3+1, JB+1,
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$ -ONE, A( J1-K2, J2 ), LDA,
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$ WORK( (J3-J1+1)+K1*N ), N,
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$ ONE, A( J2, J3 ), LDA )
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END DO
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*
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* Recover T( J, J+1 )
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*
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A( J, J+1 ) = CONJG( ALPHA )
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END IF
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*
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* WORK(J+1, 1) stores H(J+1, 1)
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*
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CALL CCOPY( N-J, A( J+1, J+1 ), LDA, WORK( 1 ), 1 )
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END IF
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GO TO 10
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ELSE
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*
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* .....................................................
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* Factorize A as L*D*L**H using the lower triangle of A
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* .....................................................
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*
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* copy first column A(1:N, 1) into H(1:N, 1)
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* (stored in WORK(1:N))
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*
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CALL CCOPY( N, A( 1, 1 ), 1, WORK( 1 ), 1 )
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*
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* J is the main loop index, increasing from 1 to N in steps of
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* JB, where JB is the number of columns factorized by CLAHEF;
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* JB is either NB, or N-J+1 for the last block
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*
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J = 0
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11 CONTINUE
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IF( J.GE.N )
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$ GO TO 20
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*
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* each step of the main loop
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* J is the last column of the previous panel
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* J1 is the first column of the current panel
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* K1 identifies if the previous column of the panel has been
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* explicitly stored, e.g., K1=1 for the first panel, and
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* K1=0 for the rest
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*
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J1 = J+1
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JB = MIN( N-J1+1, NB )
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K1 = MAX(1, J)-J
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*
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* Panel factorization
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*
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CALL CLAHEF_AA( UPLO, 2-K1, N-J, JB,
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$ A( J+1, MAX(1, J) ), LDA,
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$ IPIV( J+1 ), WORK, N, WORK( N*NB+1 ) )
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*
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* Adjust IPIV and apply it back (J-th step picks (J+1)-th pivot)
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*
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DO J2 = J+2, MIN(N, J+JB+1)
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IPIV( J2 ) = IPIV( J2 ) + J
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IF( (J2.NE.IPIV(J2)) .AND. ((J1-K1).GT.2) ) THEN
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CALL CSWAP( J1-K1-2, A( J2, 1 ), LDA,
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$ A( IPIV(J2), 1 ), LDA )
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END IF
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END DO
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J = J + JB
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*
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* Trailing submatrix update, where
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* A(J2+1, J1-1) stores L(J2+1, J1) and
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* WORK(J2+1, 1) stores H(J2+1, 1)
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*
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IF( J.LT.N ) THEN
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*
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* if the first panel and JB=1 (NB=1), then nothing to do
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*
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IF( J1.GT.1 .OR. JB.GT.1 ) THEN
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*
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* Merge rank-1 update with BLAS-3 update
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*
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ALPHA = CONJG( A( J+1, J ) )
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A( J+1, J ) = ONE
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CALL CCOPY( N-J, A( J+1, J-1 ), 1,
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$ WORK( (J+1-J1+1)+JB*N ), 1 )
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CALL CSCAL( N-J, ALPHA, WORK( (J+1-J1+1)+JB*N ), 1 )
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*
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* K1 identifies if the previous column of the panel has been
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* explicitly stored, e.g., K1=0 and K2=1 for the first panel,
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* and K1=1 and K2=0 for the rest
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*
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IF( J1.GT.1 ) THEN
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*
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* Not first panel
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*
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K2 = 1
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ELSE
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*
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* First panel
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*
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K2 = 0
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*
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* First update skips the first column
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*
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JB = JB - 1
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END IF
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*
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DO J2 = J+1, N, NB
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NJ = MIN( NB, N-J2+1 )
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*
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* Update (J2, J2) diagonal block with CGEMV
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*
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J3 = J2
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DO MJ = NJ-1, 1, -1
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CALL CGEMM( 'No transpose', 'Conjugate transpose',
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$ MJ, 1, JB+1,
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$ -ONE, WORK( (J3-J1+1)+K1*N ), N,
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$ A( J3, J1-K2 ), LDA,
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$ ONE, A( J3, J3 ), LDA )
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J3 = J3 + 1
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END DO
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*
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* Update off-diagonal block of J2-th block column with CGEMM
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*
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CALL CGEMM( 'No transpose', 'Conjugate transpose',
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$ N-J3+1, NJ, JB+1,
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$ -ONE, WORK( (J3-J1+1)+K1*N ), N,
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$ A( J2, J1-K2 ), LDA,
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$ ONE, A( J3, J2 ), LDA )
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END DO
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*
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* Recover T( J+1, J )
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*
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A( J+1, J ) = CONJG( ALPHA )
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END IF
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*
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* WORK(J+1, 1) stores H(J+1, 1)
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*
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CALL CCOPY( N-J, A( J+1, J+1 ), 1, WORK( 1 ), 1 )
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END IF
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GO TO 11
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END IF
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*
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20 CONTINUE
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WORK( 1 ) = LWKOPT
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RETURN
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*
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* End of CHETRF_AA
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*
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END
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