sqrt13.f

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      SUBROUTINE sqrt13( SCALE, M, N, A, LDA, NORMA, ISEED )
*
*  -- LAPACK test routine (version 3.1) --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*     November 2006
*
*     .. Scalar Arguments ..
      INTEGER            lda, m, n, scale
      REAL               norma
*     ..
*     .. Array Arguments ..
      INTEGER            iseed( 4 )
      REAL               a( lda, * )
*     ..
*
*  Purpose
*  =======
*
*  SQRT13 generates a full-rank matrix that may be scaled to have large
*  or small norm.
*
*  Arguments
*  =========
*
*  SCALE   (input) INTEGER
*          SCALE = 1: normally scaled matrix
*          SCALE = 2: matrix scaled up
*          SCALE = 3: matrix scaled down
*
*  M       (input) INTEGER
*          The number of rows of the matrix A.
*
*  N       (input) INTEGER
*          The number of columns of A.
*
*  A       (output) REAL array, dimension (LDA,N)
*          The M-by-N matrix A.
*
*  LDA     (input) INTEGER
*          The leading dimension of the array A.
*
*  NORMA   (output) REAL
*          The one-norm of A.
*
*  ISEED   (input/output) integer array, dimension (4)
*          Seed for random number generator
*
*  =====================================================================
*
*     .. Parameters ..
      REAL               one
      parameter( one = 1.0e0 )
*     ..
*     .. Local Scalars ..
      INTEGER            info, j
      REAL               bignum, smlnum
*     ..
*     .. External Functions ..
      REAL               sasum, slamch, slange
      EXTERNAL           sasum, slamch, slange
*     ..
*     .. External Subroutines ..
      EXTERNAL           slabad, slarnv, slascl
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          sign
*     ..
*     .. Local Arrays ..
      REAL               dummy( 1 )
*     ..
*     .. Executable Statements ..
*
      IF( m.LE.0 .OR. n.LE.0 )
     $   return
*
*     benign matrix
*
      DO 10 j = 1, n
         CALL slarnv( 2, iseed, m, a( 1, j ) )
         IF( j.LE.m ) THEN
            a( j, j ) = a( j, j ) + sign( sasum( m, a( 1, j ), 1 ),
     $                  a( j, j ) )
         END IF
   10 continue
*
*     scaled versions
*
      IF( scale.NE.1 ) THEN
         norma = slange( 'Max', m, n, a, lda, dummy )
         smlnum = slamch( 'Safe minimum' )
         bignum = one / smlnum
         CALL slabad( smlnum, bignum )
         smlnum = smlnum / slamch( 'Epsilon' )
         bignum = one / smlnum
*
         IF( scale.EQ.2 ) THEN
*
*           matrix scaled up
*
            CALL slascl( 'General', 0, 0, norma, bignum, m, n, a, lda,
     $                   info )
         ELSE IF( scale.EQ.3 ) THEN
*
*           matrix scaled down
*
            CALL slascl( 'General', 0, 0, norma, smlnum, m, n, a, lda,
     $                   info )
         END IF
      END IF
*
      norma = slange( 'One-norm', m, n, a, lda, dummy )
      return
*
*     End of SQRT13
*
      END