SUBROUTINE DLAUUMF( UPLO, N, A, LDA, INFO )

*

*  -- LAPACK auxiliary routine (version 3.0) --

*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,

*     Courant Institute, Argonne National Lab, and Rice University

*     February 29, 1992

*

*     .. Scalar Arguments ..

      CHARACTER          UPLO

      INTEGER            INFO, LDA, N

*     ..

*     .. Array Arguments ..

      DOUBLE PRECISION   A( LDA, * )

*     ..

*

*  Purpose

*  =======

*

*  DLAUUM computes the product U * U' or L' * 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 blocked form of the algorithm, calling Level 3 BLAS.

*

*  Arguments

*  =========

*

*  UPLO    (input) CHARACTER*1

*          Specifies whether the triangular factor stored in the array A

*          is upper or lower triangular:

*          = 'U':  Upper triangular

*          = 'L':  Lower triangular

*

*  N       (input) INTEGER

*          The order of the triangular factor U or L.  N >= 0.

*

*  A       (input/output) DOUBLE PRECISION 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';

*          if UPLO = 'L', the lower triangle of A is overwritten with

*          the lower triangle of the product L' * L.

*

*  LDA     (input) INTEGER

*          The leading dimension of the array A.  LDA >= max(1,N).

*

*  INFO    (output) INTEGER

*          = 0: successful exit

*          < 0: if INFO = -k, the k-th argument had an illegal value

*

*  =====================================================================

*

*     .. Parameters ..

      DOUBLE PRECISION   ONE

      PARAMETER          ( ONE = 1.0D+0 )

*     ..

*     .. Local Scalars ..

      LOGICAL            UPPER

      INTEGER            I, IB, NB

*     ..

*     .. External Functions ..

      LOGICAL            LSAME

      EXTERNAL           LSAME

*     ..

*     .. External Subroutines ..

      EXTERNAL           DGEMM, DLAUU2, DSYRK, DTRMM, XERBLA

*     ..

*     .. Intrinsic Functions ..

      INTRINSIC          MAX, MIN

*     ..

*     .. 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( 'DLAUUM', -INFO )

         RETURN

      END IF

*

*     Quick return if possible

*

      IF( N.EQ.0 )

     $   RETURN

*

*     Determine the block size for this environment.

*

      NB = 128

*

      IF( NB.LE.1 .OR. NB.GE.N ) THEN

*

*        Use unblocked code

*

         CALL DLAUU2( UPLO, N, A, LDA, INFO )

      ELSE

*

*        Use blocked code

*

         IF( UPPER ) THEN

*

*           Compute the product U * U'.

*

            DO 10 I = 1, N, NB

               IB = MIN( NB, N-I+1 )

               CALL DTRMM( 'Right', 'Upper', 'Transpose', 'Non-unit',

     $                     I-1, IB, ONE, A( I, I ), LDA, A( 1, I ),

     $                     LDA )

               CALL DLAUU2( 'Upper', IB, A( I, I ), LDA, INFO )

               IF( I+IB.LE.N ) THEN

                  CALL DGEMM( 'No transpose', 'Transpose', I-1, IB,

     $                        N-I-IB+1, ONE, A( 1, I+IB ), LDA,

     $                        A( I, I+IB ), LDA, ONE, A( 1, I ), LDA )

                  CALL DSYRK( 'Upper', 'No transpose', IB, N-I-IB+1,

     $                        ONE, A( I, I+IB ), LDA, ONE, A( I, I ),

     $                        LDA )

               END IF

   10       CONTINUE

         ELSE

*

*           Compute the product L' * L.

*

            DO 20 I = 1, N, NB

               IB = MIN( NB, N-I+1 )

               CALL DTRMM( 'Left', 'Lower', 'Transpose', 'Non-unit', IB,

     $                     I-1, ONE, A( I, I ), LDA, A( I, 1 ), LDA )

               CALL DLAUU2( 'Lower', IB, A( I, I ), LDA, INFO )

               IF( I+IB.LE.N ) THEN

                  CALL DGEMM( 'Transpose', 'No transpose', IB, I-1,

     $                        N-I-IB+1, ONE, A( I+IB, I ), LDA,

     $                        A( I+IB, 1 ), LDA, ONE, A( I, 1 ), LDA )

                  CALL DSYRK( 'Lower', 'Transpose', IB, N-I-IB+1, ONE,

     $                        A( I+IB, I ), LDA, ONE, A( I, I ), LDA )

               END IF

   20       CONTINUE

         END IF

      END IF

*

      RETURN

*

*     End of DLAUUM

*

      END