▁is ▁chosen ▁with ▁the ▁few est ▁cross es , ▁that ▁is , ▁with ▁fewer ▁inter sections ▁of ▁two ▁ma ppings . ▁From ▁the ▁two ▁align ments ▁shown , ▁alignment ▁( a ) ▁would ▁be ▁selected ▁at ▁this ▁point . ▁St ages ▁are ▁run ▁consec ut ively ▁and ▁each ▁stage ▁only ▁adds ▁to ▁the ▁alignment ▁those ▁un igr ams ▁which ▁have ▁not ▁been ▁matched ▁in ▁previous ▁stages . ▁Once ▁the ▁final ▁alignment ▁is ▁computed , ▁the ▁score ▁is ▁computed ▁as ▁follows : ▁Un ig ram ▁precision ▁ ▁is ▁calculated ▁as : ▁ ▁Where ▁ ▁is ▁the ▁number ▁of ▁un igr ams ▁in ▁the ▁candidate ▁translation ▁that ▁are ▁also ▁found ▁in ▁the ▁reference ▁translation , ▁and ▁ ▁is ▁the ▁number ▁of ▁un igr ams ▁in ▁the ▁candidate ▁translation . ▁Un ig ram ▁recall ▁ ▁is ▁computed ▁as : ▁ ▁Where ▁ ▁is ▁as ▁above , ▁and ▁ ▁is ▁the ▁number ▁of ▁un igr ams ▁in ▁the ▁reference ▁translation . ▁P rec ision ▁and ▁recall ▁are ▁combined ▁using ▁the ▁harm onic ▁mean ▁in ▁the ▁following ▁fashion , ▁with ▁recall ▁weight ed ▁ 9 ▁times ▁more ▁than ▁precision : ▁ ▁The ▁measures ▁that ▁have ▁been ▁introduced ▁so ▁far ▁only ▁account ▁for ▁con gru ity ▁with ▁respect ▁to ▁single ▁words ▁but ▁not ▁with ▁respect ▁to ▁larger ▁segments ▁that ▁appear ▁in ▁both ▁the ▁reference ▁and ▁the ▁candidate ▁sentence . ▁In ▁order ▁to ▁take ▁these ▁into ▁account , ▁longer ▁n - gram ▁matches ▁are ▁used ▁to ▁compute ▁a ▁penalty ▁ ▁for ▁the ▁alignment . ▁The ▁more ▁ma ppings ▁there ▁are