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En route pour la 4.0.15 !

    1:       SUBROUTINE DSWAP(N,DX,INCX,DY,INCY)
    2: *     .. Scalar Arguments ..
    3:       INTEGER INCX,INCY,N
    4: *     ..
    5: *     .. Array Arguments ..
    6:       DOUBLE PRECISION DX(*),DY(*)
    7: *     ..
    8: *
    9: *  Purpose
   10: *  =======
   11: *
   12: *     interchanges two vectors.
   13: *     uses unrolled loops for increments equal one.
   14: *
   15: *  Further Details
   16: *  ===============
   17: *
   18: *     jack dongarra, linpack, 3/11/78.
   19: *     modified 12/3/93, array(1) declarations changed to array(*)
   20: *
   21: *  =====================================================================
   22: *
   23: *     .. Local Scalars ..
   24:       DOUBLE PRECISION DTEMP
   25:       INTEGER I,IX,IY,M,MP1
   26: *     ..
   27: *     .. Intrinsic Functions ..
   28:       INTRINSIC MOD
   29: *     ..
   30:       IF (N.LE.0) RETURN
   31:       IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20
   32: *
   33: *       code for unequal increments or equal increments not equal
   34: *         to 1
   35: *
   36:       IX = 1
   37:       IY = 1
   38:       IF (INCX.LT.0) IX = (-N+1)*INCX + 1
   39:       IF (INCY.LT.0) IY = (-N+1)*INCY + 1
   40:       DO 10 I = 1,N
   41:           DTEMP = DX(IX)
   42:           DX(IX) = DY(IY)
   43:           DY(IY) = DTEMP
   44:           IX = IX + INCX
   45:           IY = IY + INCY
   46:    10 CONTINUE
   47:       RETURN
   48: *
   49: *       code for both increments equal to 1
   50: *
   51: *
   52: *       clean-up loop
   53: *
   54:    20 M = MOD(N,3)
   55:       IF (M.EQ.0) GO TO 40
   56:       DO 30 I = 1,M
   57:           DTEMP = DX(I)
   58:           DX(I) = DY(I)
   59:           DY(I) = DTEMP
   60:    30 CONTINUE
   61:       IF (N.LT.3) RETURN
   62:    40 MP1 = M + 1
   63:       DO 50 I = MP1,N,3
   64:           DTEMP = DX(I)
   65:           DX(I) = DY(I)
   66:           DY(I) = DTEMP
   67:           DTEMP = DX(I+1)
   68:           DX(I+1) = DY(I+1)
   69:           DY(I+1) = DTEMP
   70:           DTEMP = DX(I+2)
   71:           DX(I+2) = DY(I+2)
   72:           DY(I+2) = DTEMP
   73:    50 CONTINUE
   74:       RETURN
   75:       END