Add doc for HGQ (#1117)

* add hgq doc

* Fix wording and style

Author: calad0i

docs/advanced/hgq.rst

@@ -0,0 +1,49 @@
+===================================
+High Granularity Quantization (HGQ)
+===================================
+
+.. image:: https://github.com/calad0i/HGQ/actions/workflows/sphinx-build.yml/badge.svg
+   :target: https://calad0i.github.io/HGQ/
+.. image:: https://badge.fury.io/py/hgq.svg
+   :target: https://badge.fury.io/py/hgq
+.. image:: https://img.shields.io/badge/arXiv-2405.00645-b31b1b.svg
+   :target: https://arxiv.org/abs/2405.00645
+
+`High Granularity Quantization (HGQ) <https://github.com/calad0i/HGQ/>`_ is a library that performs gradient-based automatic bitwidth optimization and quantization-aware training algorithm for neural networks to be deployed on FPGAs. By laveraging gradients, it allows for bitwidth optimization at arbitrary granularity, up to per-weight and per-activation level.
+
+.. image:: https://calad0i.github.io/HGQ/_images/overview.svg
+   :alt: Overview of HGQ
+   :align: center
+
+Conversion of models made with HGQ library is fully supported. The HGQ models are first converted to proxy model format, which can then be parsed by hls4ml bit-accurately. Below is an example of how to create a model with HGQ and convert it to hls4ml model.
+
+.. code-block:: Python
+
+   import keras
+   from HGQ.layers import HDense, HDenseBatchNorm, HQuantize
+   from HGQ import ResetMinMax, FreeBOPs
+
+   model = keras.models.Sequential([
+      HQuantize(beta=1.e-5),
+      HDenseBatchNorm(32, beta=1.e-5, activation='relu'),
+      HDenseBatchNorm(32, beta=1.e-5, activation='relu'),
+      HDense(10, beta=1.e-5),
+   ])
+
+    opt = keras.optimizers.Adam(learning_rate=0.001)
+    loss = keras.losses.SparseCategoricalCrossentropy(from_logits=True)
+    model.compile(optimizer=opt, loss=loss, metrics=['accuracy'])
+    callbacks = [ResetMinMax(), FreeBOPs()]
+
+    model.fit(..., callbacks=callbacks)
+
+    from HGQ import trace_minmax, to_proxy_model
+    from hls4ml.converters import convert_from_keras_model
+
+    trace_minmax(model, x_train, cover_factor=1.0)
+    proxy = to_proxy_model(model, aggressive=True)
+
+    model_hls = convert_from_keras_model(proxy, backend='vivado',output_dir=... ,part=...)
+
+
+An interactive example of HGQ can be found in the `kaggle notebook <https://www.kaggle.com/code/calad0i/small-jet-tagger-with-hgq-1>`_. Full documentation can be found at `calad0i.github.io/HGQ <https://calad0i.github.io/HGQ/>`_.

docs/index.rst

@@ -22,6 +22,7 @@
     :hidden:
     :caption: Advanced Features
 
+    advanced/hgq
     advanced/qonnx
     advanced/fifo_depth
     advanced/extension