mirror of https://gitlab.com/QEF/q-e.git
49 lines
1.5 KiB
Fortran
49 lines
1.5 KiB
Fortran
!----------------------------------------------------------------------
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INTEGER FUNCTION ig_local( ig, ig_l2g, sortedig_l2g, ng )
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!
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! This function computes the local index of the G vector whose
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! global index is ig. If the G vector is not local to the current
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! processor, then the function returns -1
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!
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IMPLICIT NONE
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INTEGER, INTENT(IN) :: ig
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INTEGER, INTENT(IN) :: ng
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INTEGER, INTENT(IN) :: ig_l2g( ng ), sortedig_l2g( ng )
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INTEGER :: lb, ub, i
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lb = 1 ! initialize search interval lower bound
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ub = ng ! initialize search interval upper bound
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IF( ig < ig_l2g( sortedig_l2g(lb) ) .OR. ig > ig_l2g( sortedig_l2g(ub) ) )THEN
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ig_local = -1
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RETURN
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END IF
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BINARY_SEARCH: DO
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i = lb + (ub - lb)/2
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IF( ig >= ig_l2g( sortedig_l2g(i) ) )THEN
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lb = i
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ELSE IF( ig < ig_l2g( sortedig_l2g(i) ) )THEN
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ub = i
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ELSE
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lb = ub
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END IF
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IF( lb >= (ub-1) ) EXIT BINARY_SEARCH
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END DO BINARY_SEARCH
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IF( .NOT. ( (lb==ub) .OR. (lb==(ub-1)) ) )THEN
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CALL errore(' ig_local ',' algorithmic error ', 5)
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END IF
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IF( ig == ig_l2g( sortedig_l2g(lb) ) )THEN
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ig_local = sortedig_l2g(lb)
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ELSE IF( ig == ig_l2g( sortedig_l2g(ub) ) )THEN
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ig_local = sortedig_l2g(ub)
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ELSE
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ig_local = -1
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END IF
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RETURN
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END FUNCTION ig_local
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