SUBROUTINE DSCAL(N,DA,DX,INCX) * .. Scalar Arguments .. DOUBLE PRECISION DA INTEGER INCX,N * .. * .. Array Arguments .. DOUBLE PRECISION DX(*) * .. * * Purpose * ======= * * DSCAL scales a vector by a constant. * uses unrolled loops for increment equal to one. * * Further Details * =============== * * jack dongarra, linpack, 3/11/78. * modified 3/93 to return if incx .le. 0. * modified 12/3/93, array(1) declarations changed to array(*) * * ===================================================================== * * .. Local Scalars .. INTEGER I,M,MP1,NINCX * .. * .. Intrinsic Functions .. INTRINSIC MOD * .. IF (N.LE.0 .OR. INCX.LE.0) RETURN IF (INCX.EQ.1) GO TO 20 * * code for increment not equal to 1 * NINCX = N*INCX DO 10 I = 1,NINCX,INCX DX(I) = DA*DX(I) 10 CONTINUE RETURN * * code for increment equal to 1 * * * clean-up loop * 20 M = MOD(N,5) IF (M.EQ.0) GO TO 40 DO 30 I = 1,M DX(I) = DA*DX(I) 30 CONTINUE IF (N.LT.5) RETURN 40 MP1 = M + 1 DO 50 I = MP1,N,5 DX(I) = DA*DX(I) DX(I+1) = DA*DX(I+1) DX(I+2) = DA*DX(I+2) DX(I+3) = DA*DX(I+3) DX(I+4) = DA*DX(I+4) 50 CONTINUE RETURN END