Suggestions on training on English to Vietnamese translation

[sugeeth14]

Hi ,
I am trying on English to Vietnamese translation using IWLST data from Stanford NLP which has 133K pairs. I want to replicate results presented here tensorflow/tensor2tensor#611 where Transformer base architecture is used. I have a few quick questions

• Can preparation of data be done same as prepare-iwslt14.sh or whether it is better if learn_bpe.py is done on a larger wikipedia dump and apply_bpe.py on the smaller corpus mentioned above. Are 133k sentences alone sufficient to learn bpe so that I can just use the pre-processing script or should go for latter case. Also since moses doesn't support Vietnamese how to proceed about tokenization.

• Whether to use --joined-dictionary or not during preprocessing. As I see here it is better to use joined dictionary if the alphabets are shared. In Vietnamese I felt there are more diacritics as compared to German where joined dictionary is used without ambiguity.

• Also I used the below command on EN-DE to get good results for 4.5 million sentence pairs from WMT.
  CUDA_VISIBLE_DEVICES=0 python train.py data-bin/wmt16_en_de_bpe32k --arch transformer_wmt_en_de --share-all-embeddings --optimizer adam --adam-betas '(0.9, 0.98)' --clip-norm 0.0 --lr-scheduler inverse_sqrt --warmup-init-lr 1e-07 --warmup-updates 4000 --lr 0.0007 --min-lr 1e-09 --criterion label_smoothed_cross_entropy --label-smoothing 0.1 --weight-decay 0.0 --max-tokens 4096 --save-dir checkpoints/en-de --update-freq 8 --no-progress-bar --log-format simple --keep-interval-updates 20
  Since the data set is small whether I can use the same architecture or use IWLST architecture for DE-EN if so in any case do I need to change any hyper parameters.

I know the questions are naive but I think it would help for new users as well who are trying on Vietnamese. I am working on single gpu setup.Please give some suggestions or leads on this kind of task and dataset.
Thanks.

[edunov]

Hi @raghava14

Unfortunately I can't give exact answers to your questions without proper experimentation, but here are some thoughts:

• Is it better to learn BPE on 133K parallel sentences or on a larger monolingual corpus: I tried both for another language pair (160K parallel sentences) and I didn't see much difference, changing BPE vocab size has generally much bigger effect.

• Whether to use --joined-dictionary: For low resource settings joined-dictionary seems to be beneficial even if vocabularies are not shared (assuming you also do --share-all-embeddings during training), if you don't share vocab make sure you use --share-decoder-input-output-embed during training.

• What architecture to pick: the pre-defined architectures we have like transformer_wmt_en_de or transformer_iwslt_de_en are tuned for particular datasets, that is we found that these architectures work best on the datasets in question. They tend to work well for other datasets of similar size, but if you want to squeeze every bit of performance, you need to tune your own architecture. That, unfortunately, requires a lot of experimentation. You'll need to try various values for these parameters:
  https://github.com/pytorch/fairseq/blob/master/fairseq/models/transformer.py#L872-L879 and see what works best.

Hope that helps...

[sugeeth14]

Hi @edunov ,
Firstly thanks a lot for suggestions I tried them following architectures for English to Vietnamese and got following results

Architecture	BLEU
IWSLT DE_EN	31
Transformer_base	26

I think it is better than the one claimed here tensorflow/tensor2tensor#611 so I am closing the issue now. But as a next step I want to see if I can increase any BLEU score with Understanding Back-Translation at Scale . But unlike Monolingual corpus you obtained from WMT18 there aren't much resources available for monolingual data in Vietnamese. I am trying to use wikipedia dump but not sure how it would work. If you have any suggestions or thoughts please share them so that I can see if there can be any improvement in BLEU. Thanks again for the help.

[jiachangliu]

Hi @raghava14 ,

I tried IWSLT_DE_EN architecture for translation from English to Vietnamese. I'm able to produce BLEU score 26.86. Did you use joint dictionary or separate dictionary?

[sugeeth14]

Hi @jiachangliu I used --joined-dictionary for English to Vietnamese translation.

[jiachangliu]

@raghava14 Thank you very much. I used separate dictionaries. I will try --joined-dictionary to see if I can get better results.