slaswp.f

Go to the documentation of this file.

*> \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/ 
*
*> \htmlonly
*> Download SLASWP + dependencies 
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slaswp.f"> 
*> [TGZ]</a> 
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/slaswp.f"> 
*> [ZIP]</a> 
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slaswp.f"> 
*> [TXT]</a>
*> \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
*>          The last element of IPIV for which a row interchange will
*>          be done.
*> \endverbatim
*>
*> \param[in] IPIV
*> \verbatim
*>          IPIV is INTEGER array, dimension (K2*abs(INCX))
*>          The vector of pivot indices.  Only the elements in positions
*>          K1 through K2 of IPIV are accessed.
*>          IPIV(K) = 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 IPIV
*>          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. 
*
*> \date September 2012
*
*> \ingroup realOTHERauxiliary
*
*> \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 (version 3.4.2) --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     September 2012
*
*     .. 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(I) 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 = 1 + ( 1-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