The only code released by the 'Paragraph Vector' paper authors was a small patch, from Mikolov, that added paragraph-vectors to the original `word2vec.c` implementation in a very simple way: treating the 1st token of each line as a special paragraph-vector, still string-named (and allocated in the same lookup dictionary). Only by convention (a special prefix on those paragraph-vector tokens) could collisions with similarly-named word-vectors avoided.
That's a nice minimal way to demo/test the idea, but limited and fragile in other ways. The initial gensim implementation did something similar, then I changed it to use a separate doc-vectors space, to better support a lot of options (including the PV-DM mode with a concatenative input layer – which has never been confirmed to perform as well as the original paper implied).
That's a nice minimal way to demo/test the idea, but limited and fragile in other ways. The initial gensim implementation did something similar, then I changed it to use a separate doc-vectors space, to better support a lot of options (including the PV-DM mode with a concatenative input layer – which has never been confirmed to perform as well as the original paper implied).