slapmt.f

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      SUBROUTINE SLAPMT( FORWRD, M, N, X, LDX, K )
*
*  -- LAPACK auxiliary routine (version 3.2) --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     November 2006
*
*     .. Scalar Arguments ..
      LOGICAL            FORWRD
      INTEGER            LDX, M, N
*     ..
*     .. Array Arguments ..
      INTEGER            K( * )
      REAL               X( LDX, * )
*     ..
*
*  Purpose
*  =======
*
*  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.
*
*  Arguments
*  =========
*
*  FORWRD  (input) LOGICAL
*          = .TRUE., forward permutation
*          = .FALSE., backward permutation
*
*  M       (input) INTEGER
*          The number of rows of the matrix X. M >= 0.
*
*  N       (input) INTEGER
*          The number of columns of the matrix X. N >= 0.
*
*  X       (input/output) REAL array, dimension (LDX,N)
*          On entry, the M by N matrix X.
*          On exit, X contains the permuted matrix X.
*
*  LDX     (input) INTEGER
*          The leading dimension of the array X, LDX >= MAX(1,M).
*
*  K       (input/output) 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.
*
*  =====================================================================
*
*     .. 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