SUBROUTINE SLASWPF( N, A, LDA, K1, K2, IPIV, INCX )

*

*  -- LAPACK auxiliary routine (version 3.0) --

*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,

*     Courant Institute, Argonne National Lab, and Rice University

*     June 30, 1999

*

*     .. Scalar Arguments ..

      INTEGER            INCX, K1, K2, LDA, N

*     ..

*     .. Array Arguments ..

      INTEGER            IPIV( * )

      REAL               A( LDA, * )

*     ..

*

*  Purpose

*  =======

*

*  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.

*

*  Arguments

*  =========

*

*  N       (input) INTEGER

*          The number of columns of the matrix A.

*

*  A       (input/output) 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.

*

*  LDA     (input) INTEGER

*          The leading dimension of the array A.

*

*  K1      (input) INTEGER

*          The first element of IPIV for which a row interchange will

*          be done.

*

*  K2      (input) INTEGER

*          The last element of IPIV for which a row interchange will

*          be done.

*

*  IPIV    (input) INTEGER array, dimension (M*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.

*

*  INCX    (input) INTEGER

*          The increment between successive values of IPIV.  If IPIV

*          is negative, the pivots are applied in reverse order.

*

*  Further Details

*  ===============

*

*  Modified by

*   R. C. Whaley, Computer Science Dept., Univ. of Tenn., Knoxville, USA

*

* =====================================================================

*

*     .. 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