slapmt.f

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*> \brief \b SLAPMT performs a forward or backward permutation of the columns of a matrix.
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
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*> [TXT]</a>
*> \endhtmlonly
*
*  Definition:
*  ===========
*
*       SUBROUTINE SLAPMT( FORWRD, M, N, X, LDX, K )
*
*       .. Scalar Arguments ..
*       LOGICAL            FORWRD
*       INTEGER            LDX, M, N
*       ..
*       .. Array Arguments ..
*       INTEGER            K( * )
*       REAL               X( LDX, * )
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> SLAPMT rearranges the columns of the M by N matrix X as specified
*> by the permutation K(1),K(2),...,K(N) of the integers 1,...,N.
*> If FORWRD = .TRUE.,  forward permutation:
*>
*>      X(*,K(J)) is moved X(*,J) for J = 1,2,...,N.
*>
*> If FORWRD = .FALSE., backward permutation:
*>
*>      X(*,J) is moved to X(*,K(J)) for J = 1,2,...,N.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] FORWRD
*> \verbatim
*>          FORWRD is LOGICAL
*>          = .TRUE., forward permutation
*>          = .FALSE., backward permutation
*> \endverbatim
*>
*> \param[in] M
*> \verbatim
*>          M is INTEGER
*>          The number of rows of the matrix X. M >= 0.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>          The number of columns of the matrix X. N >= 0.
*> \endverbatim
*>
*> \param[in,out] X
*> \verbatim
*>          X is REAL array, dimension (LDX,N)
*>          On entry, the M by N matrix X.
*>          On exit, X contains the permuted matrix X.
*> \endverbatim
*>
*> \param[in] LDX
*> \verbatim
*>          LDX is INTEGER
*>          The leading dimension of the array X, LDX >= MAX(1,M).
*> \endverbatim
*>
*> \param[in,out] K
*> \verbatim
*>          K is INTEGER array, dimension (N)
*>          On entry, K contains the permutation vector. K is used as
*>          internal workspace, but reset to its original value on
*>          output.
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup lapmt
*
*  =====================================================================
      SUBROUTINE slapmt( FORWRD, M, N, X, LDX, K )
*
*  -- 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 ..
      LOGICAL            FORWRD
      INTEGER            LDX, M, N
*     ..
*     .. Array Arguments ..
      INTEGER            K( * )
      REAL               X( LDX, * )
*     ..
*
*  =====================================================================
*
*     .. Local Scalars ..
      INTEGER            I, II, J, IN
      REAL               TEMP
*     ..
*     .. Executable Statements ..
*
      IF( n.LE.1 )
     $   RETURN
*
      DO 10 i = 1, n
         k( i ) = -k( i )
   10 CONTINUE
*
      IF( forwrd ) THEN
*
*        Forward permutation
*
         DO 60 i = 1, n
*
            IF( k( i ).GT.0 )
     $         GO TO 40
*
            j = i
            k( j ) = -k( j )
            in = k( j )
*
   20       CONTINUE
            IF( k( in ).GT.0 )
     $         GO TO 40
*
            DO 30 ii = 1, m
               temp = x( ii, j )
               x( ii, j ) = x( ii, in )
               x( ii, in ) = temp
   30       CONTINUE
*
            k( in ) = -k( in )
            j = in
            in = k( in )
            GO TO 20
*
   40       CONTINUE
*
   60    CONTINUE
*
      ELSE
*
*        Backward permutation
*
         DO 110 i = 1, n
*
            IF( k( i ).GT.0 )
     $         GO TO 100
*
            k( i ) = -k( i )
            j = k( i )
   80       CONTINUE
            IF( j.EQ.i )
     $         GO TO 100
*
            DO 90 ii = 1, m
               temp = x( ii, i )
               x( ii, i ) = x( ii, j )
               x( ii, j ) = temp
   90       CONTINUE
*
            k( j ) = -k( j )
            j = k( j )
            GO TO 80
*
  100       CONTINUE
 
  110    CONTINUE
*
      END IF
*
      RETURN
*
*     End of SLAPMT
*
      END