trunk/blas/dswap.f

      SUBROUTINE  DSWAP (N,DX,INCX,DY,INCY)
C
C     INTERCHANGES TWO VECTORS.
C     USES UNROLLED LOOPS FOR INCREMENTS EQUAL ONE.
C     JACK DONGARRA, LINPACK, 3/11/78.
C
      DOUBLE PRECISION DX(*),DY(*),DTEMP
      INTEGER I,INCX,INCY,IX,IY,M,MP1,N
C
      IF(N.LE.0)RETURN
      IF(INCX.EQ.1.AND.INCY.EQ.1)GO TO 20
C
C       CODE FOR UNEQUAL INCREMENTS OR EQUAL INCREMENTS NOT EQUAL
C         TO 1
C
      IX = 1
      IY = 1
      IF(INCX.LT.0)IX = (-N+1)*INCX + 1
      IF(INCY.LT.0)IY = (-N+1)*INCY + 1
      DO 10 I = 1,N
    DTEMP = DX(IX)
    DX(IX) = DY(IY)
    DY(IY) = DTEMP
    IX = IX + INCX
    IY = IY + INCY
   10 CONTINUE
      RETURN
C
C       CODE FOR BOTH INCREMENTS EQUAL TO 1
C
C
C       CLEAN-UP LOOP
C
   20 M = MOD(N,3)
      IF( M .EQ. 0 ) GO TO 40
      DO 30 I = 1,M
    DTEMP = DX(I)
    DX(I) = DY(I)
    DY(I) = DTEMP
   30 CONTINUE
      IF( N .LT. 3 ) RETURN
   40 MP1 = M + 1
      DO 50 I = MP1,N,3
    DTEMP = DX(I)
    DX(I) = DY(I)
    DY(I) = DTEMP
    DTEMP = DX(I + 1)
    DX(I + 1) = DY(I + 1)
    DY(I + 1) = DTEMP
    DTEMP = DX(I + 2)
    DX(I + 2) = DY(I + 2)
    DY(I + 2) = DTEMP
   50 CONTINUE
      RETURN
      END
1	aw0a	1	SUBROUTINE DSWAP (N,DX,INCX,DY,INCY)
2			C
3			C INTERCHANGES TWO VECTORS.
4			C USES UNROLLED LOOPS FOR INCREMENTS EQUAL ONE.
5			C JACK DONGARRA, LINPACK, 3/11/78.
6			C
7			DOUBLE PRECISION DX(),DY(),DTEMP
8			INTEGER I,INCX,INCY,IX,IY,M,MP1,N
9			C
10			IF(N.LE.0)RETURN
11			IF(INCX.EQ.1.AND.INCY.EQ.1)GO TO 20
12			C
13			C CODE FOR UNEQUAL INCREMENTS OR EQUAL INCREMENTS NOT EQUAL
14			C TO 1
15			C
16			IX = 1
17			IY = 1
18			IF(INCX.LT.0)IX = (-N+1)*INCX + 1
19			IF(INCY.LT.0)IY = (-N+1)*INCY + 1
20			DO 10 I = 1,N
21			DTEMP = DX(IX)
22			DX(IX) = DY(IY)
23			DY(IY) = DTEMP
24			IX = IX + INCX
25			IY = IY + INCY
26			10 CONTINUE
27			RETURN
28			C
29			C CODE FOR BOTH INCREMENTS EQUAL TO 1
30			C
31			C
32			C CLEAN-UP LOOP
33			C
34			20 M = MOD(N,3)
35			IF( M .EQ. 0 ) GO TO 40
36			DO 30 I = 1,M
37			DTEMP = DX(I)
38			DX(I) = DY(I)
39			DY(I) = DTEMP
40			30 CONTINUE
41			IF( N .LT. 3 ) RETURN
42			40 MP1 = M + 1
43			DO 50 I = MP1,N,3
44			DTEMP = DX(I)
45			DX(I) = DY(I)
46			DY(I) = DTEMP
47			DTEMP = DX(I + 1)
48			DX(I + 1) = DY(I + 1)
49			DY(I + 1) = DTEMP
50			DTEMP = DX(I + 2)
51			DX(I + 2) = DY(I + 2)
52			DY(I + 2) = DTEMP
53			50 CONTINUE
54			RETURN
55			END