44 lines
1016 B
Fortran
44 lines
1016 B
Fortran
subroutine dscalf(n,da,dx,incx)
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c
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c scales a vector by a constant.
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c uses unrolled loops for increment equal to one.
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c jack dongarra, linpack, 3/11/78.
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c modified 3/93 to return if incx .le. 0.
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c modified 12/3/93, array(1) declarations changed to array(*)
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c
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double precision da,dx(*)
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integer i,incx,m,mp1,n,nincx
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c
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if( n.le.0 .or. incx.le.0 )return
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if(incx.eq.1)go to 20
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c
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c code for increment not equal to 1
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c
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nincx = n*incx
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do 10 i = 1,nincx,incx
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dx(i) = da*dx(i)
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10 continue
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return
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c
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c code for increment equal to 1
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c
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c
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c clean-up loop
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c
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20 m = mod(n,5)
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if( m .eq. 0 ) go to 40
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do 30 i = 1,m
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dx(i) = da*dx(i)
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30 continue
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if( n .lt. 5 ) return
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40 mp1 = m + 1
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do 50 i = mp1,n,5
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dx(i) = da*dx(i)
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dx(i + 1) = da*dx(i + 1)
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dx(i + 2) = da*dx(i + 2)
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dx(i + 3) = da*dx(i + 3)
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dx(i + 4) = da*dx(i + 4)
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50 continue
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return
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end
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