Like Word2vec is not a single algorithm but combination of two, namely, CBOW and Skip-Gram model; is Doc2Vec also a combination of any such algorithms? Or is it an algorithm in itself?
Word2Vec is not a combination of two models, rather both are variants of word2vec. Similarly doc2vec has Distributed Memory(DM) model and Distributed Bag of words (DBOW) model. Based on the context words and the target word, these variants arised.
Note: the name of the model maybe confusing
Distriubted Bag of wordsis similar to
Distributed Memoryis similar to
Continuous bag of words model
Distributed Memory model preserves the word order in a document whereas Distributed Bag of words just uses the bag of words approach, which doesn't preserve any word order.
This has been explained in details in this research paper.