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Word2vec update before train error message. Fix #1162 #1205

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merged 3 commits into from
Mar 13, 2017
Merged

Word2vec update before train error message. Fix #1162 #1205

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a1b29f0
added err msg
hemavakade Mar 11, 2017
956dbbd
added err msg
hemavakade Mar 11, 2017
e710159
Changed the error message
hemavakade Mar 13, 2017
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7 changes: 7 additions & 0 deletions gensim/models/word2vec.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1090,6 +1090,13 @@ def update_weights(self):
for i in xrange(len(self.wv.syn0), len(self.wv.vocab)):
# construct deterministic seed from word AND seed argument
newsyn0[i-len(self.wv.syn0)] = self.seeded_vector(self.wv.index2word[i] + str(self.seed))

# Raise an error if an online update is run before initial training on a corpus
if not len(self.wv.syn0):
raise RuntimeError("You can do an online update of vocabulary on a pre-trained model. " \
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Please start the message by stating the cause of the warning: "The model has not yet been trained."

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Note it isn't necessary any training has happened - just that no initial/prior vocabulary-discovery has happened (and the update=True case assumes that it has). So perhaps instead: "Cannot update vocabulary of model which has no prior vocabulary."

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I have updated the error message as,

"You cannot do an online vocabulary-update of a model which has no prior vocabulary. First build the vocabulary of your model with a corpus before doing an online update."

@gojomo, it does make sense to flag the error earlier than waiting till update_weights is called. I made a few changes on another file locally ( Note that this change is not currently reflected on github. It is local to me.) and tested the following code change.

    def build_vocab(self, sentences, keep_raw_vocab=False, trim_rule=None, progress_per=10000, update=False):
        """
        Build vocabulary from a sequence of sentences (can be a once-only generator stream).
        Each sentence must be a list of unicode strings.

        """
        if update:
            if not len(self.wv.vocab):
                raise RuntimeError("You cannot do an online vocabulary-update of a model which has no prior vocabulary." \
                "First build the vocabulary of your model with a corpus " \
                "before doing an online update.")        
        self.scan_vocab(sentences, progress_per=progress_per, trim_rule=trim_rule)  # initial survey
        self.scale_vocab(keep_raw_vocab=keep_raw_vocab, trim_rule=trim_rule, update=update)  # trim by min_count & precalculate downsampling
        self.finalize_vocab(update=update)  # build tables & arrays

It works well with the cases that I have mentioned earlier. I also tested this,

import gensim
from nltk.corpus import brown, movie_reviews, treebank
b_sents = brown.sents()
b = gensim.models.Word2Vec(b_sents)
b.build_vocab(b_sents, keep_raw_vocab=False, trim_rule=None, progress_per=10000, update=True)
b.train(b_sents)

Executing the will not display any error message.

"Or first build the vocabulary of your model with a corpus and train it " \
"before doing an online update.")

self.wv.syn0 = vstack([self.wv.syn0, newsyn0])

if self.hs:
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