SUBROUTINE SSWAP(N,SX,INCX,SY,INCY) * .. Scalar Arguments .. INTEGER INCX,INCY,N * .. * .. Array Arguments .. REAL SX(*),SY(*) * .. * * Purpose * ======= * * interchanges two vectors. * uses unrolled loops for increments equal to 1. * * Further Details * =============== * * jack dongarra, linpack, 3/11/78. * modified 12/3/93, array(1) declarations changed to array(*) * * ===================================================================== * * .. Local Scalars .. REAL STEMP INTEGER I,IX,IY,M,MP1 * .. * .. Intrinsic Functions .. INTRINSIC MOD * .. IF (N.LE.0) RETURN IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN * * code for both increments equal to 1 * * * clean-up loop * M = MOD(N,3) IF (M.NE.0) THEN DO I = 1,M STEMP = SX(I) SX(I) = SY(I) SY(I) = STEMP END DO IF (N.LT.3) RETURN END IF MP1 = M + 1 DO I = MP1,N,3 STEMP = SX(I) SX(I) = SY(I) SY(I) = STEMP STEMP = SX(I+1) SX(I+1) = SY(I+1) SY(I+1) = STEMP STEMP = SX(I+2) SX(I+2) = SY(I+2) SY(I+2) = STEMP END DO ELSE * * code for unequal increments or equal increments not equal * to 1 * IX = 1 IY = 1 IF (INCX.LT.0) IX = (-N+1)*INCX + 1 IF (INCY.LT.0) IY = (-N+1)*INCY + 1 DO I = 1,N STEMP = SX(IX) SX(IX) = SY(IY) SY(IY) = STEMP IX = IX + INCX IY = IY + INCY END DO END IF RETURN END