At the end of each iteration, CurrHypo is set to the concatenation of 1 best paths from each sub lattice while PrevHypo is set to the old value of CurrHypo.
if we are analyzing some i th sub-lattice in some iteration, then 1-best paths from all but this sub-lattice is kept fixed and a new 1-best path under the re-scoring LM is found out.