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subroutine dscal(n,da,dx,incx)
c
c scales a vector by a constant.
c uses unrolled loops for increment equal to one.
c jack dongarra, linpack, 3/11/78.
c modified to correct problem with negative increment, 8/21/90.
c
double precision da,dx(1)
integer i,incx,ix,m,mp1,n
c
if(n.le.0)return
if(incx.eq.1)go to 20
c
c code for increment not equal to 1
c
ix = 1
if(incx.lt.0)ix = (-n+1)*incx + 1
do 10 i = 1,n
dx(ix) = da*dx(ix)
ix = ix + incx
10 continue
return
c
c code for increment equal to 1
c
c
c clean-up loop
c
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
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