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SUBROUTINE DLASWP( N, A, LDA, K1, K2, IPIV, INCX )
*
* -- LAPACK AUXILIARY ROUTINE (VERSION 1.0B) --
* UNIV. OF TENNESSEE, UNIV. OF CALIFORNIA BERKELEY, NAG LTD.,
* COURANT INSTITUTE, ARGONNE NATIONAL LAB, AND RICE UNIVERSITY
* OCTOBER 31, 1992
*
* .. SCALAR ARGUMENTS ..
INTEGER INCX, K1, K2, LDA, N
* ..
* .. ARRAY ARGUMENTS ..
INTEGER IPIV( * )
DOUBLE PRECISION A( LDA, * )
* ..
*
* PURPOSE
* =======
*
* DLASWP 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) DOUBLE PRECISION 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.
*
* =====================================================================
*
* .. LOCAL SCALARS ..
INTEGER I, IP, IX
* ..
* .. EXTERNAL SUBROUTINES ..
EXTERNAL DSWAP
* ..
* .. EXECUTABLE STATEMENTS ..
*
* INTERCHANGE ROW I WITH ROW IPIV(I) FOR EACH OF ROWS K1 THROUGH K2.
*
IF( INCX.EQ.0 )
$ RETURN
IF( INCX.GT.0 ) THEN
IX = K1
ELSE
IX = 1 + ( 1-K2 )*INCX
END IF
IF( INCX.EQ.1 ) THEN
DO 10 I = K1, K2
IP = IPIV( I )
IF( IP.NE.I )
$ CALL DSWAP( N, A( I, 1 ), LDA, A( IP, 1 ), LDA )
10 CONTINUE
ELSE IF( INCX.GT.1 ) THEN
DO 20 I = K1, K2
IP = IPIV( IX )
IF( IP.NE.I )
$ CALL DSWAP( N, A( I, 1 ), LDA, A( IP, 1 ), LDA )
IX = IX + INCX
20 CONTINUE
ELSE IF( INCX.LT.0 ) THEN
DO 30 I = K2, K1, -1
IP = IPIV( IX )
IF( IP.NE.I )
$ CALL DSWAP( N, A( I, 1 ), LDA, A( IP, 1 ), LDA )
IX = IX + INCX
30 CONTINUE
END IF
*
RETURN
*
* END OF DLASWP
*
END
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