UnsupervisedDecomposition

PyTorch original implementation of "Unsupervised Question Decomposition for Question Answering" (EMNLP 2020).

TL;DR: We decompose hard (multi-hop) questions into several, easier (single-hop) questions using unsupervised learning. Our decompositions improve multi-hop QA on HotpotQA without requiring extra supervision to decompose questions.

Overview

XLM contains the code to train (Unsupervised) Seq2Seq models, based on the code from XLM. We made the following changes/additions:

Unsupervised stopping criterion
Tensorboard logging
Data preprocessing scripts
Minor bug fixes from original XLM code
When initializing a smaller Seq2Seq model with XLM_en pretrained weights, automatically initialize the encoder with the first XLM_en layer weights and the decoder with the remaining layer weights.

pytorch-transformers contains the code to train question answering models (single-hop and multi-hop), based on the code from transformers. We made the following additions:

Scripts/notebooks to preprocess data
Additions to evaluation to handle/evaluate on HotpotQA (i.e., extend single-paragraph SQuAD implementation to multi-paragraph setting)

10/2020: Update! added additional data and resources:

Simple and multihop mined questions
Multihop QA model checkpoints
MLM pretraining data
Unsupervised MT training data

Installation

Create an anaconda3 environment (we used anaconda3 version 5.0.1):

conda create -y -n UnsupervisedDecomposition python=3.7
conda activate UnsupervisedDecomposition
# Install PyTorch 1.0. We used CUDA 10.0 (with NCCL/2.4.7-1) (see https://pytorch.org/ to install with other CUDA versions):
conda install -y pytorch=1.0 torchvision cudatoolkit=10.0 -c pytorch
conda install faiss-gpu cudatoolkit=10.0 -c pytorch # For CUDA 10.0
pip install -r requirements.txt
python -m spacy download en_core_web_lg  # Download Spacy model for NER

If your hardware supports half-precision (fp16), you can install NVIDIA apex to speed up QA model training. Also, set the MAIN_DIR variable to point to the main directory for this repo, e.g.:

export MAIN_DIR=/path/to/UnsupervisedDecomposition

Downloading and Preprocessing Data

Run download_data.sh once, to download/prepare the necessary files for decomposition and question answering training, e.g.:

bash download_data.sh --main_dir $MAIN_DIR

See below to train a decomposition model, or skip to "QA Model Training" to train a question answering model given our trained decomposition model (XLM/dumped/umt.dev1.pseudo_decomp.replace_entity_by_type/20639223/best-valid_mlm_ppl.pth). You can view our generations from the model in the downloaded files XLM/dumped/umt.dev1.pseudo_decomp.replace_entity_by_type/20639223/hyp.st=0.0.bs=5.lp=1.0.es=False.seed=0.mh-sh.{train|valid}.pred.bleu.sh.txt.

Unsupervised Decomposition Training

Create pseudo-decomposition training data using FastText embeddings and entity replacement using create_pseudo_decompositions.sh , e.g.:

bash create_pseudo_decompositions.sh --main_dir $MAIN_DIR

Then, train an Unsupervised Seq2Seq model as follows (initializing from our pre-trained MLM model):

# Set the following parameters based on your hardware
export NPROC_PER_NODE=8  # Use 1 for single-GPU training
export N_NODES=1  # Use >1 for multi-node training (where each node has NPROC_PER_NODE GPUs)
BS=32  # Make batch size smaller if GPU goes out-of-memory. Effective batch size is BS*NPROC_PER_NODE*N_NODES

# Select an MLM initialization checkpoint (for now, let's load the MLM we already pre-trained)
MLM_INIT=dumped/mlm.dev1.pseudo_decomp_random.mined/best-valid_mlm_ppl.pth 

# Train USeq2Seq model
export NGPU=$NPROC_PER_NODE
if [[ $NPROC_PER_NODE -gt 1 ]]; then DIST_OPTS="-m torch.distributed.launch --nproc_per_node=$NPROC_PER_NODE"; else DIST_OPTS=""; fi
NUM_TRAIN=`wc -l < data/umt/$DATA_FOLDER/processed/train.mh`
python $DIST_OPTS train.py --exp_name umt.$DATA_FOLDER --data_path data/umt/$DATA_FOLDER/processed --dump_path ./dumped/ --reload_model "$MLM_INIT,$MLM_INIT" --encoder_only false --emb_dim 2048 --n_layers 6 --n_heads 16 --dropout 0.1 --attention_dropout 0.1 --gelu_activation true --use_lang_emb true --lgs 'mh-sh' --ae_steps 'mh,sh' --bt_steps 'mh-sh-mh,sh-mh-sh' --stopping_criterion 'valid_mh-sh-mh_mt_effective_goods_back_bleu,2' --validation_metrics 'valid_mh-sh-mh_mt_effective_goods_back_bleu' --eval_bleu true --epoch_size $((4*NUM_TRAIN/(NPROC_PER_NODE*N_NODES))) --lambda_ae '0:1,100000:0.1,300000:0' --optimizer 'adam_inverse_sqrt,beta1=0.9,beta2=0.98,lr=0.00003' --tokens_per_batch 1024 --batch_size $BS --word_shuffle 3 --word_dropout 0.1 --word_blank 0.1 --max_len 128 --bptt 128 --save_periodic 0 --split_data true --validation_weight 0.5

New: to train UMT with the same data we used, download our splits here

Seq2Seq Decomposition Training (Optional)

Alternatively, you can train a standard Seq2Seq model as follows:

export NPROC_PER_NODE=8  # Use 1 for single-GPU training
export N_NODES=1  # Use >1 for multi-node training (where each node has NPROC_PER_NODE GPUs)
BS=128  # Make batch size smaller if GPU goes out-of-memory. Effective batch size is BS*NPROC_PER_NODE*N_NODES

MLM_INIT=dumped/mlm.dev1.pseudo_decomp_random.mined/best-valid_mlm_ppl.pth
export NGPU=$NPROC_PER_NODE
if [[ $NPROC_PER_NODE -gt 1 ]]; then DIST_OPTS="-m torch.distributed.launch --nproc_per_node=$NPROC_PER_NODE"; else DIST_OPTS=""; fi
DATA_FOLDER=dev1.pseudo_decomp.replace_entity_by_type
DATA_PATH=data/umt/$DATA_FOLDER/processed
NUM_TRAIN=`wc -l < $DATA_PATH/train.mh`
mkdir -p $OUTPUT_DIR
python $DIST_OPTS train.py --exp_name mt.$DATA_FOLDER --data_path $DATA_PATH --dump_path ./dumped/ --reload_model "$MLM_INIT,$MLM_INIT" --encoder_only false --emb_dim 2048 --n_layers 6 --n_heads 16 --dropout 0.1 --attention_dropout 0.1 --gelu_activation true --use_lang_emb true --lgs 'mh-sh' --mt_steps 'mh-sh,sh-mh' --stopping_criterion 'valid_mh-sh_mt_bleu,2' --validation_metrics 'valid_mh-sh_mt_bleu' --eval_bleu true --epoch_size $((2*NUM_TRAIN/(NPROC_PER_NODE*N_NODES))) --optimizer 'adam_inverse_sqrt,beta1=0.9,beta2=0.98,lr=0.0001' --tokens_per_batch 1024 --batch_size $BS --max_len 128 --bptt 128 --split_data true

You can also use the trained Seq2Seq model checkpoint as the pre-trained initialization (MLM_INIT) for USeq2Seq training, as our Curriculum Seq2Seq approach does (see Appendix).

MLM Pre-training (Optional)

New: Download MLM pretraining data here

To pre-train your own MLM initialization (used as MLM_INIT), use the below commands:

# Set the following parameters based on your hardware
export NPROC_PER_NODE=8  # Use 1 for single-GPU training
export N_NODES=8  # Use >1 for multi-node training (where each node has NPROC_PER_NODE GPUs)

# Copy XLM's English pre-trained MLM weights, which we use to initialize our MLM training
wget https://dl.fbaipublicfiles.com/XLM/mlm_en_2048.pth
mv mlm_en_2048.pth dumped/xlm_en/

# MLM pre-training (on same data as above)
export NGPU=$NPROC_PER_NODE
if [[ $NPROC_PER_NODE -gt 1 ]]; then DIST_OPTS="-m torch.distributed.launch --nproc_per_node=$NPROC_PER_NODE"; else DIST_OPTS=""; fi
EPOCH_SIZE=$((2*NUM_TRAIN))
BS=24
EFFECTIVE_BS=$((BS*NPROC_PER_NODE*N_NODES))
NUM_TRAIN=`wc -l < data/umt/$DATA_FOLDER/processed/train.mh`
# For fp16: Add "--fp16 true --amp 1" below
python $DIST_OPTS train.py --exp_name mlm.$DATA_FOLDER --data_path data/umt/$DATA_FOLDER/processed --dump_path ./dumped/ --reload_model 'dumped/xlm_en/mlm_en_2048.pth' --emb_dim 2048 --n_layers 12 --n_heads 16 --dropout 0.1 --attention_dropout 0.1 --gelu_activation true --use_lang_emb true --lgs 'mh-sh' --clm_steps '' --mlm_steps 'mh,sh' --stopping_criterion '_valid_mlm_ppl,0' --validation_metrics '_valid_mlm_ppl' --epoch_size $EPOCH_SIZE --optimizer "adam_inverse_sqrt,lr=0.00003,beta1=0.9,beta2=0.98,weight_decay=0,warmup_updates=$((EPOCH_SIZE/EFFECTIVE_BS))" --batch_size $BS --max_len 128 --bptt 128 --accumulate_gradients 1 --word_pred 0.15 --sample_alpha 0

QA Model Training

With a trained decomposition model, we can generate decompositions for multi-hop questions (train and valid sets), and train a question answering model to use the decompositions (below we use our pre-trained decomposition model which you downloaded):

# Generate decompositions
ST=0.0
LP=1.0
BEAM=5
SEED=0
# Point to model directory (change the final directory number/string/id below to match the directory string from the previous Unsupervised Seq2Seq training command)
MODEL_DIR=dumped/umt.dev1.pseudo_decomp.replace_entity_by_type/20639223
MODEL_NO="$(echo $MODEL_DIR | rev | cut -d/ -f1 | rev)"
for SPLIT in valid train; do
    # Note: Decrease batch size below if GPU goes out of memory
    cat data/umt/all/processed/$SPLIT.mh | python translate.py --exp_name translate --src_lang mh --tgt_lang sh --model_path $MODEL_DIR/best-valid_mh-sh-mh_mt_effective_goods_back_bleu.pth --output_path $MODEL_DIR/$SPLIT.pred.bleu.sh --batch_size 48 --beam_size $BEAM --length_penalty $LP --sample_temperature $ST
done

# Convert Sub-Qs to SQUAD format
cd $MAIN_DIR/pytorch-transformers
for SPLIT in valid train; do
    python umt_gen_subqs_to_squad_format.py --model_dir $MODEL_DIR --data_folder all --sample_temperature $ST --beam $BEAM --length_penalty $LP --seed $SEED --split $SPLIT --new_data_format
done

# Answer sub-Qs
DATA_FOLDER=data/hotpot.umt.all.model=$MODEL_NO.st=$ST.beam=$BEAM.lp=$LP.seed=$SEED
for SPLIT in "dev" "train"; do
for NUM_PARAGRAPHS in 1 3; do
    # For fp16: Add "--fp16 --fp16_opt_level O2" below
    python examples/run_squad.py --model_type roberta --model_name_or_path roberta-large --train_file $DATA_FOLDER/train.json --predict_file $DATA_FOLDER/$SPLIT.json --do_eval --do_lower_case --version_2_with_negative --output_dir checkpoint/roberta_large.hotpot_easy_and_squad.num_paragraphs=$NUM_PARAGRAPHS --per_gpu_train_batch_size 64 --per_gpu_eval_batch_size 32 --learning_rate 1.5e-5 --max_query_length 234 --max_seq_length 512 --doc_stride 50 --num_shards 1 --seed 0 --max_grad_norm inf --adam_epsilon 1e-6 --adam_beta_2 0.98 --weight_decay 0.01 --warmup_proportion 0.06 --num_train_epochs 2 --write_dir $DATA_FOLDER/roberta_predict.np=$NUM_PARAGRAPHS --no_answer_file
done
done

# Ensemble sub-answer predictions
for SPLIT in "dev" "train"; do
    python ensemble_answers_by_confidence_script.py --seeds_list 1 3 --no_answer_file --split $SPLIT --preds_file1 data/hotpot.umt.all.model=$MODEL_NO.st=$ST.beam=$BEAM.lp=$LP.seed=$SEED/roberta_predict.np={}/nbest_predictions_$SPLIT.json
done

# Add sub-questions and sub-answers to QA input
FLAGS="--atype sentence-1-center --subq_model roberta-large-np=1-3 --use_q --use_suba --use_subq"
python add_umt_subqs_subas_to_q_squad_format_new.py --subqs_dir data/hotpot.umt.all.model=$MODEL_NO.st=$ST.beam=$BEAM.lp=$LP.seed=$SEED --splits train dev --num_shards 1 --model_dir $MODEL_DIR --sample_temperature $ST --beam $BEAM --length_penalty $LP --seed $SEED --subsample_data --use_easy --use_squad $FLAGS

# Train QA model
export NGPU=8  # Set based on number of available GPUs
if [ $NGPU -gt 1 ]; then DIST_OPTS="-m torch.distributed.launch --nproc_per_node=$NGPU"; else DIST_OPTS=""; fi
if [ $NGPU -gt 1 ]; then EVAL_OPTS="--do_eval"; else EVAL_OPTS=""; fi
export MASTER_PORT=$(shuf -i 12001-19999 -n 1)
FLAGS_STRING="${FLAGS// --/.}"
FLAGS_STRING="${FLAGS_STRING//--/.}"
FLAGS_STRING="${FLAGS_STRING// /=}"
TN=hotpot.umt.all.model=$MODEL_NO.st=$ST.beam=$BEAM.lp=$LP.seed=$SEED$FLAGS_STRING.suba1=0.suba2=0-squad.medium_hard_frac=1.0
RANDOM_SEED=0
OUTPUT_DIR="checkpoint/tn=$TN/rs=$RANDOM_SEED"
# For fp16: Add "--fp16 --fp16_opt_level O2" below
python $DIST_OPTS examples/run_squad.py --model_type roberta --model_name_or_path roberta-large --train_file data/$TN/train.json --predict_file data/$TN/dev.json --do_train $EVAL_OPTS --do_lower_case --version_2_with_negative --output_dir $OUTPUT_DIR --per_gpu_train_batch_size $((64/NGPU)) --per_gpu_eval_batch_size 32 --learning_rate 1.5e-5 --master_port $MASTER_PORT --max_query_length 234 --max_seq_length 512 --doc_stride 50 --num_shards 1 --seed $RANDOM_SEED --max_grad_norm inf --adam_epsilon 1e-6 --adam_beta_2 0.98 --weight_decay 0.01 --warmup_proportion 0.06 --num_train_epochs 2 --overwrite_output_dir

New: our trained multihop model checkpoints are available here:

Creating Alternate Pseudo-Decompositions

We can also create pseudo-decompositions using other embedding methods aside from FastText, as described in the Appendix. To do so, use the functions in pytorch-transformers/pseudoalignment/pseudo_decomp_{paired_random|fasttext|tfidf|bert|variable}.py, e.g., by running:

python pseudoalignment/pseudo_decomp_fasttext.py \
    --split train    # decompose the hotpotQA training question
    --min_q_len 4    # minimum length of short questions (tokens)
    --max_q_len 20   # maximum length of short questions (tokens)
    --beam_size 100  # subset of short questions to search exhaustively over for each complex question
    --data_folder data/umt/decomposition_name  # path to dump the results to

The different pseudo-decomposition methods are:

pseudo_decomp_fasttext.py - decompose using bag of fasttext vectors
pseudo_decomp_random.py - randomly pair short questions (for ablations/comparisons)
pseudo_decomp_tfidf.py - decompose using bag of tfidf vectors
pseudo_decomp_variable.py - decompose using bag of facttext vectors, but using a variable number of subquestions (see Appendix)
pseudo_decomp_bert.py - decompose using bert embeddings (requires generating the bert embeddings first with embed_questions_with_bert.py)
pseudo_decomp_bert_nsp.py - decompose using bert NSP embeddings (not in the paper) (requires generating the bert embeddings first with embed_questions_with_bert.py)

Variable Number of Sub-Questions

To train a decomposition model to generate a variable number of sub-questions, you'll need to make the following changes:

Train on variable-length pseudo-decompositions, created using python pseudoalignment/pseudo_decomp_fasttext.py (see above).
Use a version of the unsupervised stopping criterion which only counts bad decompositions as those with N<2 sub-questions (as opposed to N!=2 sub-questions). Simply add the flag --one_to_variable when training (Unsupervised) Seq2Seq models with XLM/train.py.
Have the single-hop QA model answer an arbitrary number of sub-questions, instead of a maximum of 2 sub-questions. Simply add --one_to_variable to the FLAGS variable used in the "QA Model Training" section earlier.

Data mined from Common Crawl

Data mined from common crawl using our fasttext classifiers can be found here

Citation

@inproceedings{perez2020unsupervised,
    title={Unsupervised Question Decomposition for Question Answering},
    author={Ethan Perez and Patrick Lewis and Wen-tau Yih and Kyunghyun Cho and Douwe Kiela},
    year={2020},
    booktitle={EMNLP},
    url={https://arxiv.org/abs/2002.09758}
}

License

See the LICENSE file for more details.

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