[seq2seq] MAX_LEN env var for MT commands (#5837)

examples/seq2seq/README.md

@@ -78,7 +78,7 @@ The following command should work on a 16GB GPU:
     --model_name_or_path facebook/bart-large
 ```
 
-*Note*: The following tips mostly apply to summarization finetuning.
+
 
 ### Translation Finetuning
 
@@ -87,6 +87,7 @@ Then you can finetune mbart_cc25 on english-romanian with the following command.
 **Recommendation:** Read and potentially modify the fairly opinionated defaults in `train_mbart_cc25_enro.sh` script before running it. 
 ```bash
 export ENRO_DIR=${PWD}/wmt_en_ro   # may need to be fixed depending on where you downloaded
+export MAX_LEN=128
 export BS=4
 export GAS=8
 ./train_mbart_cc25_enro.sh --output_dir cc25_v1_frozen/

examples/seq2seq/train_mbart_cc25_enro.sh

@@ -8,11 +8,10 @@ python finetune.py \
     --do_train \
     --do_predict \
     --val_check_interval 0.1 \
-    --n_val 500 \
     --adam_eps 1e-06 \
     --num_train_epochs 3 --src_lang en_XX --tgt_lang ro_RO \
     --freeze_encoder --freeze_embeds --data_dir $ENRO_DIR \
-    --max_source_length=300 --max_target_length 300 --val_max_target_length=300 --test_max_target_length 300 \
+    --max_source_length $MAX_LEN --max_target_length $MAX_LEN --val_max_target_length $MAX_LEN --test_max_target_length $MAX_LEN \
     --train_batch_size=$BS --eval_batch_size=$BS --gradient_accumulation_steps=$GAS \
     --model_name_or_path facebook/mbart-large-cc25 \
     --task translation \

examples/seq2seq/train_mbart_cc25_enro_multigpu.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+export PYTHONPATH="../":"${PYTHONPATH}"
+# Need to export N_GPUS=
+python finetune.py \
+    --learning_rate=3e-5 \
+    --fp16 \
+    --gpus $N_GPUS \
+    --do_train \
+    --val_check_interval 0.25 \
+    --adam_eps 1e-06 \
+    --num_train_epochs 6 --src_lang en_XX --tgt_lang ro_RO \
+    --data_dir $ENRO_DIR \
+    --max_source_length $MAX_LEN --max_target_length $MAX_LEN --val_max_target_length $MAX_LEN --test_max_target_length $MAX_LEN \
+    --train_batch_size=$BS --eval_batch_size=$BS --gradient_accumulation_steps=$GAS \
+    --tokenizer facebook/mbart-large-cc25 \
+    --task translation \
+    --warmup_steps 500 --freeze_encoder --freeze_embeds \
+    $@