slaswp.f

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*> \brief \b SLASWP performs a series of row interchanges on a general rectangular matrix.
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
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*> \endhtmlonly
*
*  Definition:
*  ===========
*
*       SUBROUTINE SLASWP( N, A, LDA, K1, K2, IPIV, INCX )
*
*       .. Scalar Arguments ..
*       INTEGER            INCX, K1, K2, LDA, N
*       ..
*       .. Array Arguments ..
*       INTEGER            IPIV( * )
*       REAL               A( LDA, * )
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> SLASWP performs a series of row interchanges on the matrix A.
*> One row interchange is initiated for each of rows K1 through K2 of A.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>          The number of columns of the matrix A.
*> \endverbatim
*>
*> \param[in,out] A
*> \verbatim
*>          A is REAL array, dimension (LDA,N)
*>          On entry, the matrix of column dimension N to which the row
*>          interchanges will be applied.
*>          On exit, the permuted matrix.
*> \endverbatim
*>
*> \param[in] LDA
*> \verbatim
*>          LDA is INTEGER
*>          The leading dimension of the array A.
*> \endverbatim
*>
*> \param[in] K1
*> \verbatim
*>          K1 is INTEGER
*>          The first element of IPIV for which a row interchange will
*>          be done.
*> \endverbatim
*>
*> \param[in] K2
*> \verbatim
*>          K2 is INTEGER
*>          (K2-K1+1) is the number of elements of IPIV for which a row
*>          interchange will be done.
*> \endverbatim
*>
*> \param[in] IPIV
*> \verbatim
*>          IPIV is INTEGER array, dimension (K1+(K2-K1)*abs(INCX))
*>          The vector of pivot indices. Only the elements in positions
*>          K1 through K1+(K2-K1)*abs(INCX) of IPIV are accessed.
*>          IPIV(K1+(K-K1)*abs(INCX)) = L implies rows K and L are to be
*>          interchanged.
*> \endverbatim
*>
*> \param[in] INCX
*> \verbatim
*>          INCX is INTEGER
*>          The increment between successive values of IPIV. If INCX
*>          is negative, the pivots are applied in reverse order.
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup laswp
*
*> \par Further Details:
*  =====================
*>
*> \verbatim
*>
*>  Modified by
*>   R. C. Whaley, Computer Science Dept., Univ. of Tenn., Knoxville, USA
*> \endverbatim
*>
*  =====================================================================
      SUBROUTINE slaswp( N, A, LDA, K1, K2, IPIV, INCX )
*
*  -- 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 ..
      INTEGER            INCX, K1, K2, LDA, N
*     ..
*     .. Array Arguments ..
      INTEGER            IPIV( * )
      REAL               A( LDA, * )
*     ..
*
* =====================================================================
*
*     .. Local Scalars ..
      INTEGER            I, I1, I2, INC, IP, IX, IX0, J, K, N32
      REAL               TEMP
*     ..
*     .. Executable Statements ..
*
*     Interchange row I with row IPIV(K1+(I-K1)*abs(INCX)) for each of rows
*     K1 through K2.
*
      IF( incx.GT.0 ) THEN
         ix0 = k1
         i1 = k1
         i2 = k2
         inc = 1
      ELSE IF( incx.LT.0 ) THEN
         ix0 = k1 + ( k1-k2 )*incx
         i1 = k2
         i2 = k1
         inc = -1
      ELSE
         RETURN
      END IF
*
      n32 = ( n / 32 )*32
      IF( n32.NE.0 ) THEN
         DO 30 j = 1, n32, 32
            ix = ix0
            DO 20 i = i1, i2, inc
               ip = ipiv( ix )
               IF( ip.NE.i ) THEN
                  DO 10 k = j, j + 31
                     temp = a( i, k )
                     a( i, k ) = a( ip, k )
                     a( ip, k ) = temp
   10             CONTINUE
               END IF
               ix = ix + incx
   20       CONTINUE
   30    CONTINUE
      END IF
      IF( n32.NE.n ) THEN
         n32 = n32 + 1
         ix = ix0
         DO 50 i = i1, i2, inc
            ip = ipiv( ix )
            IF( ip.NE.i ) THEN
               DO 40 k = n32, n
                  temp = a( i, k )
                  a( i, k ) = a( ip, k )
                  a( ip, k ) = temp
   40          CONTINUE
            END IF
            ix = ix + incx
   50    CONTINUE
      END IF
*
      RETURN
*
*     End of SLASWP
*
      END