dqrt13.f

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*> \brief \b DQRT13
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at 
*            http://www.netlib.org/lapack/explore-html/ 
*
*  Definition:
*  ===========
*
*       SUBROUTINE DQRT13( SCALE, M, N, A, LDA, NORMA, ISEED )
* 
*       .. Scalar Arguments ..
*       INTEGER            LDA, M, N, SCALE
*       DOUBLE PRECISION   NORMA
*       ..
*       .. Array Arguments ..
*       INTEGER            ISEED( 4 )
*       DOUBLE PRECISION   A( LDA, * )
*       ..
*  
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> DQRT13 generates a full-rank matrix that may be scaled to have large
*> or small norm.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] SCALE
*> \verbatim
*>          SCALE is INTEGER
*>          SCALE = 1: normally scaled matrix
*>          SCALE = 2: matrix scaled up
*>          SCALE = 3: matrix scaled down
*> \endverbatim
*>
*> \param[in] M
*> \verbatim
*>          M is INTEGER
*>          The number of rows of the matrix A.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>          The number of columns of A.
*> \endverbatim
*>
*> \param[out] A
*> \verbatim
*>          A is DOUBLE PRECISION array, dimension (LDA,N)
*>          The M-by-N matrix A.
*> \endverbatim
*>
*> \param[in] LDA
*> \verbatim
*>          LDA is INTEGER
*>          The leading dimension of the array A.
*> \endverbatim
*>
*> \param[out] NORMA
*> \verbatim
*>          NORMA is DOUBLE PRECISION
*>          The one-norm of A.
*> \endverbatim
*>
*> \param[in,out] ISEED
*> \verbatim
*>          ISEED is integer array, dimension (4)
*>          Seed for random number generator
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee 
*> \author Univ. of California Berkeley 
*> \author Univ. of Colorado Denver 
*> \author NAG Ltd. 
*
*> \date November 2011
*
*> \ingroup double_lin
*
*  =====================================================================
      SUBROUTINE dqrt13( SCALE, M, N, A, LDA, NORMA, ISEED )
*
*  -- LAPACK test routine (version 3.4.0) --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     November 2011
*
*     .. Scalar Arguments ..
      INTEGER            lda, m, n, scale
      DOUBLE PRECISION   norma
*     ..
*     .. Array Arguments ..
      INTEGER            iseed( 4 )
      DOUBLE PRECISION   a( lda, * )
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      DOUBLE PRECISION   one
      parameter( one = 1.0d0 )
*     ..
*     .. Local Scalars ..
      INTEGER            info, j
      DOUBLE PRECISION   bignum, smlnum
*     ..
*     .. External Functions ..
      DOUBLE PRECISION   dasum, dlamch, dlange
      EXTERNAL           dasum, dlamch, dlange
*     ..
*     .. External Subroutines ..
      EXTERNAL           dlabad, dlarnv, dlascl
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          sign
*     ..
*     .. Local Arrays ..
      DOUBLE PRECISION   dummy( 1 )
*     ..
*     .. Executable Statements ..
*
      IF( m.LE.0 .OR. n.LE.0 )
     $   return
*
*     benign matrix
*
      DO 10 j = 1, n
         CALL dlarnv( 2, iseed, m, a( 1, j ) )
         IF( j.LE.m ) THEN
            a( j, j ) = a( j, j ) + sign( dasum( m, a( 1, j ), 1 ),
     $                  a( j, j ) )
         END IF
   10 continue
*
*     scaled versions
*
      IF( scale.NE.1 ) THEN
         norma = dlange( 'Max', m, n, a, lda, dummy )
         smlnum = dlamch( 'Safe minimum' )
         bignum = one / smlnum
         CALL dlabad( smlnum, bignum )
         smlnum = smlnum / dlamch( 'Epsilon' )
         bignum = one / smlnum
*
         IF( scale.EQ.2 ) THEN
*
*           matrix scaled up
*
            CALL dlascl( 'General', 0, 0, norma, bignum, m, n, a, lda,
     $                   info )
         ELSE IF( scale.EQ.3 ) THEN
*
*           matrix scaled down
*
            CALL dlascl( 'General', 0, 0, norma, smlnum, m, n, a, lda,
     $                   info )
         END IF
      END IF
*
      norma = dlange( 'One-norm', m, n, a, lda, dummy )
      return
*
*     End of DQRT13
*
      END