We can get Moses search graph by using the option -output-search-graph. Its format is explained at http://www.statmt.org/moses/?n=Moses.AdvancedFeatures. However after I have read it, I still did not understand many thing especially “covered” and “stack”. (”recombined” is not in scope of this post.) Both “covered” and “stack” are related covered foreign (source) language words. Stack is number of covered words and “covered” is referred to start and end position of covered words. These are trivial. However probably because of my English is bad, from the explanation, I did not understand that “covered” referred to “current” or “latest” translated words but “stack” is referred translated words including previous (ancestor) hypotheses too.
Example:
0 hyp=859 stack=2 back=80 score=-7.85572 transition=-1.97807 forward=11192 fscore=-16.5095 covered=4-4 out=ที่
…
0 hyp=11 stack=1 back=0 score=-5.63929 transition=-5.63929 forward=160 fscore=-15.6831 covered=0-0 out=ฉัน ไม่ รู้
…
0 hyp=80 stack=1 back=0 score=-5.87765 transition=-5.87765 forward=880 fscore=-15.1593 covered=3-3 out=กิน อาหาร
…
0 hyp=859 stack=2 back=80 score=-7.85572 transition=-1.97807 forward=11192 fscore=-16.5095 covered=4-4 out=ที่
…
…
…
For example, hypothesis 859’s stack=2 since it is include the word “eat” (3-3) from hypothesis 80 too. Previous (ancestor) hypotheses can be traced by looking at “back” (back pointer). “out” is translated string (in target language). It is directly corresponded to “covered” since “out” does not contain translated string from previous hypotheses but only current one.
In brief, “out” and “covered” is about current translation made by a hypothesis only but “stack” is about current + what are inherited from previous hypotheses (ancestors). And previous hypotheses can be traced by “back”.
