  We present Samanantar, the largest publicly available parallel corpora
collection for Indic languages. The collection contains a total of 49.7 million
sentence pairs between English and 11 Indic languages (from two language
families). Specifically, we compile 12.4 million sentence pairs from existing,
publicly-available parallel corpora, and additionally mine 37.4 million
sentence pairs from the web, resulting in a 4x increase. We mine the parallel
sentences from the web by combining many corpora, tools, and methods: (a)
web-crawled monolingual corpora, (b) document OCR for extracting sentences from
scanned documents, (c) multilingual representation models for aligning
sentences, and (d) approximate nearest neighbor search for searching in a large
collection of sentences. Human evaluation of samples from the newly mined
corpora validate the high quality of the parallel sentences across 11
languages. Further, we extract 83.4 million sentence pairs between all 55 Indic
language pairs from the English-centric parallel corpus using English as the
pivot language. We trained multilingual NMT models spanning all these languages
on Samanantar, which outperform existing models and baselines on publicly
available benchmarks, such as FLORES, establishing the utility of Samanantar.
Our data and models are available publicly at
https://ai4bharat.iitm.ac.in/samanantar and we hope they will help advance
research in NMT and multilingual NLP for Indic languages.
