It should be possible to adapt Giza's HMM implementation to produce monotone alignments. These are the changes that would be necessary (and which should be fairly easy, if you can figure out the code):
1) alignment distribution initialization. by default Giza initializes the HMM transition probabilities to be uniform (effectively making the first iteration of HMM training the same as one more iteration of Model 1). You would need to alter this to make "reverse" jumps have probability 0. 2) smoothing. by default, Giza does something to prevent probabilities from ending up zero (maybe add alpha?). This is fine for monotone jumps, but you want to make sure that "backward" jumps end up zero. I think adding this would be have tremendous value. -Chris On Thu, Aug 23, 2012 at 7:53 PM, Philipp Koehn <[email protected]> wrote: > Hi, > > the IBM Models of GIZA++ are too complicated to be used > for simple monotone alignment. I am not aware of any > switches that would allow this either. > > I suggest to look at finite state machine tools such as > OpenFST - http://www.openfst.org/ > > -phi > > On Wed, Aug 22, 2012 at 5:29 AM, Dario Ernst <[email protected]> wrote: >> Hello dear list, >> >> first off, i'm not quite sure this is the correct list to ask GIZA++ >> questions - if not, please just tell me ;). I'm sorry for the trouble in >> that case. >> >> Anyways, my question. I'm currently trying to use GIZA++ together with >> PISA (http://pisa.googlecode.com/) to create monotone (linear?) >> alignments of words and phoneme-strings. For PISA i believe i've already >> found a way (thanks to the nice help of the author!), but for GIZA i'm a >> bit at loss. Is there some external parameter that i can set, or would >> digging the source be necessary? If so (and i've already started to try >> to familiarize myself a bit with the GIZA internals), what would be a >> good starting point to look at? Unfortunately i'm not that good with >> SMT internals yet, so it'd be a bit hard for me ... so at this point any >> help, input and tips would be greatly appreciated! >> >> Best Regards from Germany (and, please excuse my bad english ;P), thanks >> for reading this ;) >> >> -- >> Man's mind, once stretched by a new idea, never regains its original >> dimensions. -- Oliver Wendell Holmes >> _______________________________________________ >> Moses-support mailing list >> [email protected] >> http://mailman.mit.edu/mailman/listinfo/moses-support > _______________________________________________ > Moses-support mailing list > [email protected] > http://mailman.mit.edu/mailman/listinfo/moses-support _______________________________________________ Moses-support mailing list [email protected] http://mailman.mit.edu/mailman/listinfo/moses-support
