Hi,

Do the following sections from Koehn's pseudocode align to the E and M  
steps of the EM algorithm?

E-Step
set count(e|f) to 0 for all e,f
set total(f) to 0 for all f
for all sentence pairs (e_s,f_s)
for all words e in e_s
total_s(e) = 0
for all words f in f_s
total_s(e) += t(e|f)
for all words e in e_s
for all words f in f_s
count(e|f) += t(e|f) / total_s(e)
total(f) += t(e|f) / total_s(e)


M-Step
for all f
for all e
t(e|f) = count(e|f) / total(f)


The reason I ask is that while I can see the parameters being updated  
in the M-Step it really doesn't look like any kind of maximisation  
logic is being applied. The section I labelled E-Step looks more like  
Maximisation logic.

Also in the section I label E-step there doesn't seem to any kind of  
alignment logic going on. Or is that what the continual update of  
counts and totals amounts to? Is this implicitly aligning words on a  
per sentence basis?

Thanks guys. I'd really appreciate an answer. It's the last week to  
dissertation hand in and I'm writing up and don't want to make any  
silly mistakes.

James

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The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.



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