30 lines
919 B
Fortran
30 lines
919 B
Fortran
integer*8 function configuration_search_key(cfg,Nint)
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use bitmasks
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implicit none
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BEGIN_DOC
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! Returns an integer*8 corresponding to a determinant index for searching.
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! The left-most 8 bits contain the number of open shells+1. This ensures that the CSF
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! are packed with the same seniority.
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END_DOC
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integer, intent(in) :: Nint
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integer(bit_kind), intent(in) :: cfg(Nint,2)
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integer :: i, n_open_shells
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integer*8 :: mask
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i = shiftr(elec_alpha_num, bit_kind_shift)+1
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configuration_search_key = int(shiftr(ior(cfg(i,1),cfg(i,2)),1)+sum(cfg),8)
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mask = int(Z'00FFFFFFFFFFFFFF',8)
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configuration_search_key = iand(mask,configuration_search_key)
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n_open_shells = 1
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do i=1,Nint
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if (cfg(i,1) == 0_bit_kind) cycle
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n_open_shells = n_open_shells + popcnt(cfg(i,1))
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enddo
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mask = n_open_shells
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mask = shiftl(mask,56)
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configuration_search_key = ior (mask,configuration_search_key)
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end
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