Retriever does not train properly on a custom dataset with empty negative_ctxs and hard_negative_ctxs

[yu-rovikov]

Hi! I've been trying to train DPR using the in-batch negatives schema on a custom dataset with no negative_ctxs and hard_negative_ctxs with default configs. It appears that the network does not train properly on such datasets. In particular, loss on every training step is 0:

It seems that the issue is indeed due to the abscence of negative examples in the dataset: when I add random positive paragraphs from other questions as negatives, the retriever seems to train properly:

However, I don't want any fixed random paragraphs as negatives in my dataset. It seems that either the in-batch negatives schema does not apply when there are no negative_ctxs, or it does not apply in the default settings at all. I was not able to find the reason in _calc_loss (train_dense_encoder.py).

Is it possible to train the retriever on such datasets? Or do I need at least one negative_ctxs for each data point? Thank you!

P.S.
The dataset I am using looks like this (two exalmples):

[{'question': 'x y : ℝ,\nh : x ≤ y\n⊢ real.sqrt x ≤ real.sqrt y',
  'positive_ctxs': [{'title': 'real.sqrt',
    'text': 'def sqrt (x : ℝ) : ℝ :=\tnnreal.sqrt (real.to_nnreal x)'},
   {'title': 'nnreal.sqrt_le_sqrt_iff',
    'text': 'lemma sqrt_le_sqrt_iff : sqrt x ≤ sqrt y ↔ x ≤ y'}],
  'negative_ctxs': [],
  'hard_negative_ctxs': []},
 {'question': 'X : Compactum,\nA B : set ↥X\n⊢ basic (A ∩ B) = basic A ∩ basic B',
  'positive_ctxs': [{'title': '<None>', 'text': '<None>'}],
  'negative_ctxs': [],
  'hard_negative_ctxs': []}]

It is designed to search relevant lemmas for automated theorem proving.

The only thing I changed in the repo is the encoder_train_default.yaml config where I added my custom dataset:

[shahad2099]

hello
I have the same problem except that my dataset contains hard_neg_examples but no hard_neg .

[yu-rovikov]

The problem was in hydra configurations. Although my biencoder_default.yaml had batch_size: 2, the script (train_dense_encoder.py) still ran with batch_size=1. I did not find a regular way to set batch_size=2 (or any other value). A temporary workaround is to run the stript from the command line as follows:

python train_dense_encoder.py train_datasets=[lean_questions_one_lemma_train] dev_datasets=[lean_questions_one_lemma_dev] train=biencoder_local output_dir=outputs train.batch_size=<NEW BATCH_SIZE>