*> \brief \b ZLAUU2 computes the product UUH or LHL, where U and L are upper or lower triangular matrices (unblocked algorithm). * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * *> \htmlonly *> Download ZLAUU2 + dependencies *> *> [TGZ] *> *> [ZIP] *> *> [TXT] *> \endhtmlonly * * Definition: * =========== * * SUBROUTINE ZLAUU2( UPLO, N, A, LDA, INFO ) * * .. Scalar Arguments .. * CHARACTER UPLO * INTEGER INFO, LDA, N * .. * .. Array Arguments .. * COMPLEX*16 A( LDA, * ) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> ZLAUU2 computes the product U * U**H or L**H * L, where the triangular *> factor U or L is stored in the upper or lower triangular part of *> the array A. *> *> If UPLO = 'U' or 'u' then the upper triangle of the result is stored, *> overwriting the factor U in A. *> If UPLO = 'L' or 'l' then the lower triangle of the result is stored, *> overwriting the factor L in A. *> *> This is the unblocked form of the algorithm, calling Level 2 BLAS. *> \endverbatim * * Arguments: * ========== * *> \param[in] UPLO *> \verbatim *> UPLO is CHARACTER*1 *> Specifies whether the triangular factor stored in the array A *> is upper or lower triangular: *> = 'U': Upper triangular *> = 'L': Lower triangular *> \endverbatim *> *> \param[in] N *> \verbatim *> N is INTEGER *> The order of the triangular factor U or L. N >= 0. *> \endverbatim *> *> \param[in,out] A *> \verbatim *> A is COMPLEX*16 array, dimension (LDA,N) *> On entry, the triangular factor U or L. *> On exit, if UPLO = 'U', the upper triangle of A is *> overwritten with the upper triangle of the product U * U**H; *> if UPLO = 'L', the lower triangle of A is overwritten with *> the lower triangle of the product L**H * L. *> \endverbatim *> *> \param[in] LDA *> \verbatim *> LDA is INTEGER *> The leading dimension of the array A. LDA >= max(1,N). *> \endverbatim *> *> \param[out] INFO *> \verbatim *> INFO is INTEGER *> = 0: successful exit *> < 0: if INFO = -k, the k-th argument had an illegal value *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \ingroup complex16OTHERauxiliary * * ===================================================================== SUBROUTINE ZLAUU2( UPLO, N, A, LDA, INFO ) * * -- LAPACK auxiliary routine -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * * .. Scalar Arguments .. CHARACTER UPLO INTEGER INFO, LDA, N * .. * .. Array Arguments .. COMPLEX*16 A( LDA, * ) * .. * * ===================================================================== * * .. Parameters .. COMPLEX*16 ONE PARAMETER ( ONE = ( 1.0D+0, 0.0D+0 ) ) * .. * .. Local Scalars .. LOGICAL UPPER INTEGER I DOUBLE PRECISION AII * .. * .. External Functions .. LOGICAL LSAME COMPLEX*16 ZDOTC EXTERNAL LSAME, ZDOTC * .. * .. External Subroutines .. EXTERNAL XERBLA, ZDSCAL, ZGEMV, ZLACGV * .. * .. Intrinsic Functions .. INTRINSIC DBLE, DCMPLX, MAX * .. * .. Executable Statements .. * * Test the input parameters. * INFO = 0 UPPER = LSAME( UPLO, 'U' ) 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 END IF IF( INFO.NE.0 ) THEN CALL XERBLA( 'ZLAUU2', -INFO ) RETURN END IF * * Quick return if possible * IF( N.EQ.0 ) \$ RETURN * IF( UPPER ) THEN * * Compute the product U * U**H. * DO 10 I = 1, N AII = DBLE( A( I, I ) ) IF( I.LT.N ) THEN A( I, I ) = AII*AII + DBLE( ZDOTC( N-I, A( I, I+1 ), LDA, \$ A( I, I+1 ), LDA ) ) CALL ZLACGV( N-I, A( I, I+1 ), LDA ) CALL ZGEMV( 'No transpose', I-1, N-I, ONE, A( 1, I+1 ), \$ LDA, A( I, I+1 ), LDA, DCMPLX( AII ), \$ A( 1, I ), 1 ) CALL ZLACGV( N-I, A( I, I+1 ), LDA ) ELSE CALL ZDSCAL( I, AII, A( 1, I ), 1 ) END IF 10 CONTINUE * ELSE * * Compute the product L**H * L. * DO 20 I = 1, N AII = DBLE( A( I, I ) ) IF( I.LT.N ) THEN A( I, I ) = AII*AII + DBLE( ZDOTC( N-I, A( I+1, I ), 1, \$ A( I+1, I ), 1 ) ) CALL ZLACGV( I-1, A( I, 1 ), LDA ) CALL ZGEMV( 'Conjugate transpose', N-I, I-1, ONE, \$ A( I+1, 1 ), LDA, A( I+1, I ), 1, \$ DCMPLX( AII ), A( I, 1 ), LDA ) CALL ZLACGV( I-1, A( I, 1 ), LDA ) ELSE CALL ZDSCAL( I, AII, A( I, 1 ), LDA ) END IF 20 CONTINUE END IF * RETURN * * End of ZLAUU2 * END