Annotation of rpl/lapack/blas/dswap.f, revision 1.1
1.1 ! bertrand 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
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