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    1:       SUBROUTINE ZLAUU2( UPLO, N, A, LDA, INFO )
    2: *
    3: *  -- LAPACK auxiliary routine (version 3.2) --
    4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
    5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
    6: *     November 2006
    7: *
    8: *     .. Scalar Arguments ..
    9:       CHARACTER          UPLO
   10:       INTEGER            INFO, LDA, N
   11: *     ..
   12: *     .. Array Arguments ..
   13:       COMPLEX*16         A( LDA, * )
   14: *     ..
   15: *
   16: *  Purpose
   17: *  =======
   18: *
   19: *  ZLAUU2 computes the product U * U' or L' * L, where the triangular
   20: *  factor U or L is stored in the upper or lower triangular part of
   21: *  the array A.
   22: *
   23: *  If UPLO = 'U' or 'u' then the upper triangle of the result is stored,
   24: *  overwriting the factor U in A.
   25: *  If UPLO = 'L' or 'l' then the lower triangle of the result is stored,
   26: *  overwriting the factor L in A.
   27: *
   28: *  This is the unblocked form of the algorithm, calling Level 2 BLAS.
   29: *
   30: *  Arguments
   31: *  =========
   32: *
   33: *  UPLO    (input) CHARACTER*1
   34: *          Specifies whether the triangular factor stored in the array A
   35: *          is upper or lower triangular:
   36: *          = 'U':  Upper triangular
   37: *          = 'L':  Lower triangular
   38: *
   39: *  N       (input) INTEGER
   40: *          The order of the triangular factor U or L.  N >= 0.
   41: *
   42: *  A       (input/output) COMPLEX*16 array, dimension (LDA,N)
   43: *          On entry, the triangular factor U or L.
   44: *          On exit, if UPLO = 'U', the upper triangle of A is
   45: *          overwritten with the upper triangle of the product U * U';
   46: *          if UPLO = 'L', the lower triangle of A is overwritten with
   47: *          the lower triangle of the product L' * L.
   48: *
   49: *  LDA     (input) INTEGER
   50: *          The leading dimension of the array A.  LDA >= max(1,N).
   51: *
   52: *  INFO    (output) INTEGER
   53: *          = 0: successful exit
   54: *          < 0: if INFO = -k, the k-th argument had an illegal value
   55: *
   56: *  =====================================================================
   57: *
   58: *     .. Parameters ..
   59:       COMPLEX*16         ONE
   60:       PARAMETER          ( ONE = ( 1.0D+0, 0.0D+0 ) )
   61: *     ..
   62: *     .. Local Scalars ..
   63:       LOGICAL            UPPER
   64:       INTEGER            I
   65:       DOUBLE PRECISION   AII
   66: *     ..
   67: *     .. External Functions ..
   68:       LOGICAL            LSAME
   69:       COMPLEX*16         ZDOTC
   70:       EXTERNAL           LSAME, ZDOTC
   71: *     ..
   72: *     .. External Subroutines ..
   73:       EXTERNAL           XERBLA, ZDSCAL, ZGEMV, ZLACGV
   74: *     ..
   75: *     .. Intrinsic Functions ..
   76:       INTRINSIC          DBLE, DCMPLX, MAX
   77: *     ..
   78: *     .. Executable Statements ..
   79: *
   80: *     Test the input parameters.
   81: *
   82:       INFO = 0
   83:       UPPER = LSAME( UPLO, 'U' )
   84:       IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
   85:          INFO = -1
   86:       ELSE IF( N.LT.0 ) THEN
   87:          INFO = -2
   88:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
   89:          INFO = -4
   90:       END IF
   91:       IF( INFO.NE.0 ) THEN
   92:          CALL XERBLA( 'ZLAUU2', -INFO )
   93:          RETURN
   94:       END IF
   95: *
   96: *     Quick return if possible
   97: *
   98:       IF( N.EQ.0 )
   99:      $   RETURN
  100: *
  101:       IF( UPPER ) THEN
  102: *
  103: *        Compute the product U * U'.
  104: *
  105:          DO 10 I = 1, N
  106:             AII = A( I, I )
  107:             IF( I.LT.N ) THEN
  108:                A( I, I ) = AII*AII + DBLE( ZDOTC( N-I, A( I, I+1 ), LDA,
  109:      $                     A( I, I+1 ), LDA ) )
  110:                CALL ZLACGV( N-I, A( I, I+1 ), LDA )
  111:                CALL ZGEMV( 'No transpose', I-1, N-I, ONE, A( 1, I+1 ),
  112:      $                     LDA, A( I, I+1 ), LDA, DCMPLX( AII ),
  113:      $                     A( 1, I ), 1 )
  114:                CALL ZLACGV( N-I, A( I, I+1 ), LDA )
  115:             ELSE
  116:                CALL ZDSCAL( I, AII, A( 1, I ), 1 )
  117:             END IF
  118:    10    CONTINUE
  119: *
  120:       ELSE
  121: *
  122: *        Compute the product L' * L.
  123: *
  124:          DO 20 I = 1, N
  125:             AII = A( I, I )
  126:             IF( I.LT.N ) THEN
  127:                A( I, I ) = AII*AII + DBLE( ZDOTC( N-I, A( I+1, I ), 1,
  128:      $                     A( I+1, I ), 1 ) )
  129:                CALL ZLACGV( I-1, A( I, 1 ), LDA )
  130:                CALL ZGEMV( 'Conjugate transpose', N-I, I-1, ONE,
  131:      $                     A( I+1, 1 ), LDA, A( I+1, I ), 1,
  132:      $                     DCMPLX( AII ), A( I, 1 ), LDA )
  133:                CALL ZLACGV( I-1, A( I, 1 ), LDA )
  134:             ELSE
  135:                CALL ZDSCAL( I, AII, A( I, 1 ), LDA )
  136:             END IF
  137:    20    CONTINUE
  138:       END IF
  139: *
  140:       RETURN
  141: *
  142: *     End of ZLAUU2
  143: *
  144:       END