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qp2/src/utils/extrapolation.irp.f

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2019-01-25 11:39:31 +01:00
subroutine extrapolate_data(N_data, data, pt2, output)
implicit none
BEGIN_DOC
! Extrapolate the data to the FCI limit
END_DOC
integer, intent(in) :: N_data
double precision, intent(in) :: data(N_data)
double precision, intent(in) :: pt2(N_data)
double precision, intent(out) :: output(N_data)
double precision :: data_rev(N_data), pt2_rev(N_data)
integer :: ifit, i,j
double precision :: ab(2), x(N_data,2), x_inv(2,N_data), y(N_data)
do i=1,N_data
data_rev(N_data+1-i) = data(i)
pt2_rev(N_data+1-i) = pt2(i)
enddo
do i=1,N_data
y(i) = data_rev(i)
x(i,1) = 1.d0
x(i,2) = pt2_rev(i)
enddo
do ifit=2,N_data
call get_pseudo_inverse(x,size(x,1),ifit,2,x_inv,size(x_inv,1))
ab = matmul(x_inv(1:2,1:ifit),y(1:ifit))
output(ifit) = ab(1)
enddo
end