55 lines
1.4 KiB
Fortran
55 lines
1.4 KiB
Fortran
double precision function shank_general(array,n,nmax)
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implicit none
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integer, intent(in) :: n,nmax
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double precision, intent(in) :: array(0:nmax) ! array of the partial sums
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integer :: ntmp,i
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double precision :: sum(0:nmax),shank1(0:nmax)
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if(n.lt.3)then
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print*,'You asked to Shank a sum but the order is smaller than 3 ...'
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print*,'n = ',n
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print*,'stopping ....'
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stop
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endif
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ntmp = n
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sum = array
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i = 0
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do while(ntmp.ge.2)
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i += 1
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! print*,'i = ',i
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call shank(sum,ntmp,nmax,shank1)
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ntmp = ntmp - 2
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sum = shank1
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shank_general = shank1(ntmp)
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enddo
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end
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subroutine shank(array,n,nmax,shank1)
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implicit none
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integer, intent(in) :: n,nmax
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double precision, intent(in) :: array(0:nmax)
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double precision, intent(out) :: shank1(0:nmax)
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integer :: i,j
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double precision :: shank_function
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do i = 1, n-1
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shank1(i-1) = shank_function(array,i,nmax)
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enddo
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end
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double precision function shank_function(array,i,n)
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implicit none
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integer, intent(in) :: i,n
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double precision, intent(in) :: array(0:n)
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double precision :: b_n, b_n1
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b_n = array(i) - array(i-1)
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b_n1 = array(i+1) - array(i)
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if(dabs(b_n1-b_n).lt.1.d-12)then
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shank_function = array(i+1)
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else
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shank_function = array(i+1) - b_n1*b_n1/(b_n1-b_n)
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endif
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end
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