Update README.

README.md

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+---
+language: "en"
+tags:
+- icefall
+- k2
+- transducer
+- aishell
+- ASR
+- stateless transducer
+- PyTorch
+license: "apache-2.0"
+datasets:
+- aishell
+metrics:
+- WER
+---
+
+# Introduction
+
+This repo contains pre-trained model using
+<https://github.com/k2-fsa/icefall/pull/219>.
+
+It is trained on [AIShell](https://www.openslr.org/33/) dataset
+using modified transducer from [optimized_transducer](https://github.com/csukuangfj/optimized_transducer).
+
+## How to clone this repo
+```
+sudo apt-get install git-lfs
+git clone https://huggingface.co/csukuangfj/icefall-aishell-transducer-stateless-modified-2022-03-01
+
+cd icefall-aishell-transducer-stateless-modified-2022-03-01
+git lfs pull
+```
+
+**Catuion**: You have to run `git lfs pull`. Otherwise, you will be SAD later.
+
+The model in this repo is trained using the commit `TODO`.
+
+You can use
+
+```
+git clone https://github.com/k2-fsa/icefall
+cd icefall
+git checkout TODO
+```
+to download `icefall`.
+
+You can find the model information by visiting <https://github.com/k2-fsa/icefall/blob/TODO/egs/aishell/ASR/transducer_stateless_modified/train.py#L232>.
+
+
+In short, the encoder is a Conformer model with 8 heads, 12 encoder layers, 512-dim attention, 2048-dim feedforward;
+the decoder contains a 512-dim embedding layer and a Conv1d with kernel size 2.
+
+The decoder architecture is modified from
+[Rnn-Transducer with Stateless Prediction Network](https://ieeexplore.ieee.org/document/9054419).
+A Conv1d layer is placed right after the input embedding layer.
+
+-----
+
+## Description
+
+This repo provides pre-trained transducer Conformer model for the AIShell dataset
+using [icefall][icefall]. There are no RNNs in the decoder. The decoder is stateless
+and contains only an embedding layer and a Conv1d.
+
+The commands for training are:
+
+```bash
+cd egs/aishell/ASR
+./prepare.sh --stop-stage 6
+
+export CUDA_VISIBLE_DEVICES="0,1,2"
+
+./transducer_stateless_modified/train.py \
+  --world-size 3 \
+  --num-epochs 90 \
+  --start-epoch 0 \
+  --exp-dir transducer_stateless_modified/exp-4 \
+  --max-duration 250 \
+  --lr-factor 2.0 \
+  --context-size 2 \
+  --modified-transducer-prob 0.25
+```
+
+The tensorboard training log can be found at
+<https://tensorboard.dev/experiment/C27M8YxRQCa1t2XglTqlWg>
+
+The commands for decoding are
+
+```bash
+# greedy search
+for epoch in 64; do
+  for avg in 33; do
+  ./transducer_stateless_modified-2/decode.py \
+    --epoch $epoch \
+    --avg $avg \
+    --exp-dir transducer_stateless_modified/exp-4 \
+    --max-duration 100 \
+    --context-size 2 \
+    --decoding-method greedy_search \
+    --max-sym-per-frame 1
+  done
+done
+
+# modified beam search
+for epoch in 64; do
+  for avg in 33; do
+    ./transducer_stateless_modified/decode.py \
+    --epoch $epoch \
+    --avg $avg \
+    --exp-dir transducer_stateless_modified/exp-4 \
+    --max-duration 100 \
+    --context-size 2 \
+    --decoding-method modified_beam_search \
+    --beam-size 4
+  done
+done
+```
+
+You can find the decoding log for the above command in this
+repo (in the folder [log][log]).
+
+The WER for the test dataset is
+
+|                        | test |comment                                                         |
+|------------------------|------|----------------------------------------------------------------|
+| greedy search          | 5.22 |--epoch 64, --avg 33, --max-duration 100, --max-sym-per-frame 1 |
+| modified beam search   | 5.02 |--epoch 64, --avg 33, --max-duration 100  --beam-size 4         |
+
+# File description
+
+- [log][log], this directory contains the decoding log and decoding results
+- [test_wavs][test_wavs], this directory contains wave files for testing the pre-trained model
+- [data][data], this directory contains files generated by [prepare.sh][prepare]
+- [exp][exp], this directory contains only one file: `preprained.pt`
+
+`exp/pretrained.pt` is generated by the following command:
+
+```bash
+epoch=64
+avg=33
+
+./transducer_stateless_modified/export.py \
+  --exp-dir ./transducer_stateless_modified/exp-4 \
+  --lang-dir ./data/lang_char \
+  --epoch $epoch \
+  --avg $avg
+```
+
+**HINT**: To use `pretrained.pt` to compute the WER for the `test` dataset,
+just do the following:
+
+```bash
+cp icefall-aishell-transducer-stateless-modified-2022-03-01/exp/pretrained.pt \
+  /path/to/icefall/egs/aishell/ASR/transducer_stateless_modified/exp/epoch-999.pt
+```
+and pass `--epoch 999 --avg 1` to `transducer_stateless_modified/decode.py`.
+
+
+[icefall]: https://github.com/k2-fsa/icefall
+[prepare]: https://github.com/k2-fsa/icefall/blob/master/egs/aishell/ASR/prepare.sh
+[exp]: https://huggingface.co/csukuangfj/icefall-aishell-transducer-stateless-modified-2022-03-01/tree/main/exp
+[data]: https://huggingface.co/csukuangfj/icefall-aishell-transducer-stateless-modified-2022-03-01/tree/main/data
+[test_wavs]: https://huggingface.co/csukuangfj/icefall-aishell-transducer-stateless-modified-2022-03-01/tree/main/test_wavs
+[log]: https://huggingface.co/csukuangfj/icefall-aishell-transducer-stateless-modified-2022-03-01/tree/main/log
+[icefall]: https://github.com/k2-fsa/icefall