Fast N-Gram LM on GPU + greedy decoding (RNN-T, TDT, CTC)
State: open | Pull request: yes
Labels: name: core

name: ASR

# What does this PR do ?

Add a one line overview of what this PR aims to accomplish.

**Collection**: [Note which collection this PR will affect]

# Changelog 
- Add specific line by line info of high level changes in this PR.

# Usage
* You can potentially add a usage example below

```python
# Add a code snippet demonstrating how to use this 
```

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# Before your PR is "Ready for review"
**Pre checks**:
- [x] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [ ] Did you write any new necessary tests?
- [ ] Did you add or update any necessary documentation?
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  - [ ] Reviewer: Does the PR have correct import guards for all optional libraries?
  
**PR Type**:
- [x] New Feature
- [ ] Bugfix
- [ ] Documentation

If you haven't finished some of the above items you can still open "Draft" PR.


## Who can review?

Anyone in the community is free to review the PR once the checks have passed. 
[Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md) contains specific people who can review PRs to various areas.

# Additional Information
* Related to # (issue)


<!-- pylint-output-strict-mode-true -->

beep boop 🤖: 🚨 The following files must be fixed before merge!

---

Your code was analyzed with PyLint. The following annotations have been identified:

```
************* Module nemo.collections.asr.parts.submodules.ngram_lm
nemo/collections/asr/parts/submodules/ngram_lm.py:85:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ngram_lm.py:94:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ngram_lm.py:97:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ngram_lm.py:147:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ngram_lm.py:168:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/parts/submodules/ngram_lm.py:251:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ngram_lm.py:350:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ngram_lm.py:474:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ngram_lm.py:671:4: C0116: Missing function or method docstring (missing-function-docstring)

-----------------------------------
Your code has been rated at 9.83/10
```

---

Mitigation guide:

* Add sensible and useful docstrings to functions and methods
* For trivial methods like getter/setters, consider adding `# pylint: disable=C0116` inside the function itself
* To disable multiple functions/methods at once, put a `# pylint: disable=C0116` before the first and a `# pylint: enable=C0116` after the last.

By applying these rules, we reduce the occurance of this message in future.

Thank you for improving NeMo's documentation!

<!-- pylint-output-strict-mode-false -->

beep boop 🤖: 🙏 The following files have warnings. In case you are familiar with these, please try helping us to improve the code base.

---

Your code was analyzed with PyLint. The following annotations have been identified:

```
************* Module nemo.collections.asr.parts.submodules.ctc_decoding
nemo/collections/asr/parts/submodules/ctc_decoding.py:370:0: C0301: Line too long (136/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_decoding.py:764:0: C0301: Line too long (151/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_decoding.py:921:0: C0301: Line too long (125/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_decoding.py:33:0: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_decoding.py:995:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_decoding.py:1006:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_decoding.py:1017:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_decoding.py:1477:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/asr/parts/submodules/ctc_decoding.py:1524:0: C0115: Missing class docstring (missing-class-docstring)
************* Module nemo.collections.asr.parts.submodules.ctc_greedy_decoding
nemo/collections/asr/parts/submodules/ctc_greedy_decoding.py:63:0: C0301: Line too long (247/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_greedy_decoding.py:162:0: C0301: Line too long (123/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_greedy_decoding.py:171:0: C0301: Line too long (205/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_greedy_decoding.py:399:0: C0301: Line too long (123/119) (line-too-long)
nemo/collections/asr/parts/submodules/ctc_greedy_decoding.py:30:0: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/asr/parts/submodules/ctc_greedy_decoding.py:643:0: C0115: Missing class docstring (missing-class-docstring)
************* Module nemo.collections.asr.parts.submodules.rnnt_loop_labels_computer
nemo/collections/asr/parts/submodules/rnnt_loop_labels_computer.py:198:4: C0115: Missing class docstring (missing-class-docstring)
************* Module nemo.collections.asr.parts.submodules.tdt_loop_labels_computer
nemo/collections/asr/parts/submodules/tdt_loop_labels_computer.py:204:4: C0115: Missing class docstring (missing-class-docstring)
************* Module scripts.asr_language_modeling.ngram_lm.train_kenlm
scripts/asr_language_modeling/ngram_lm/train_kenlm.py:66:0: C0301: Line too long (169/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/train_kenlm.py:77:0: C0301: Line too long (128/119) (line-too-long)
scripts/asr_language_modeling/ngram_lm/train_kenlm.py:83:0: C0116: Missing function or method docstring (missing-function-docstring)

-----------------------------------
Your code has been rated at 9.93/10
```

---

Mitigation guide:

* Add sensible and useful docstrings to functions and methods
* For trivial methods like getter/setters, consider adding `# pylint: disable=C0116` inside the function itself
* To disable multiple functions/methods at once, put a `# pylint: disable=C0116` before the first and a `# pylint: enable=C0116` after the last.

By applying these rules, we reduce the occurance of this message in future.

Thank you for improving NeMo's documentation!