hls4ml: `TypeError` occurs when calling `hls_model.compile()`

Quick summary

I’m currently trying to create an HLS project for the PYNQ-ZU starting from the DeepTrack package. Specifically I’m attempting to implement as a starting point the single particle tracking example within the package. After defining the configuration and the HLS model though, compile() generates a TypeError.

Details

• I replicate in a separate notebook the entirety of the single particle tracking example model created with DeepTrack.
• I define the configuration and the HLS model using as part the part name of the Zynq UltraScale+ chip on the PYNQ-ZU board.

Using hls4ml.utils.plot_model(hls_model, show_shapes=True, show_precision=True, to_file=None) the plotted model is shown as follows:

Steps to Reproduce

1. pip install deeptrack
2. pip install hls4ml
3. Create a Jupyter notebook starting from the single particle example (link in the quick summary)
4. Add the following code as next steps:

import plotting
from hls4ml.converters import convert_from_keras_model
from hls4ml.utils import config_from_keras_model
from pprint import pprint

config = config_from_keras_model(model=model, granularity="model")
hls_model = convert_from_keras_model(
    model=model,
    output_dir="./deeptrack_model/hls4ml_prj",
    project_name="deep_track_spt",
    part="XCZU5EG-SFVC784"
)

hls_model.compile()

Expected behavior

The model should compile without problems.

Actual behavior

The current traceback is generated:

Writing HLS project
Output exceeds the [size limit](command:workbench.action.openSettings?[). Open the full output data [in a text editor](command:workbench.action.openLargeOutput?1688e68f-2cf1-45f7-b1b7-a2a874d20238)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/home/jacopo/workspace/hls4ml/deeptrack_with_hls4ml.ipynb Cell 23 in <cell line: 1>()
----> [1](vscode-notebook-cell://wsl%2Bubuntu-18.04/home/jacopo/workspace/hls4ml/deeptrack_with_hls4ml.ipynb#ch0000022vscode-remote?line=0) hls_model.compile()

File ~/.local/lib/python3.8/site-packages/hls4ml/model/hls_model.py:526, in HLSModel.compile(self)
    525 def compile(self):
--> 526     self.write()
    528     curr_dir = os.getcwd()
    529     os.chdir(self.config.get_output_dir())

File ~/.local/lib/python3.8/site-packages/hls4ml/model/hls_model.py:523, in HLSModel.write(self)
    519     return ''.join(choice(hexdigits) for m in range(length))
    521 self.config.config['Stamp'] = make_stamp()
--> 523 self.config.writer.write_hls(self)

File ~/.local/lib/python3.8/site-packages/hls4ml/writer/vivado_writer.py:682, in VivadoWriter.write_hls(self, model)
    680 self.write_build_script(model)
    681 self.write_nnet_utils(model)
--> 682 self.write_yml(model)
    683 self.write_tar(model)
    684 print('Done')

File ~/.local/lib/python3.8/site-packages/hls4ml/writer/vivado_writer.py:660, in VivadoWriter.write_yml(self, model)
    657     pass
    659 with open(model.config.get_output_dir() + '/' + config_filename, 'w') as file:
--> 660     yaml.dump(model.config.config, file)

File /usr/lib/python3/dist-packages/yaml/__init__.py:200, in dump(data, stream, Dumper, **kwds)
    195 def dump(data, stream=None, Dumper=Dumper, **kwds):
    196     """
    197     Serialize a Python object into a YAML stream.
    198     If stream is None, return the produced string instead.
    199     """
--> 200     return dump_all([data], stream, Dumper=Dumper, **kwds)

File /usr/lib/python3/dist-packages/yaml/__init__.py:188, in dump_all(documents, stream, Dumper, default_style, default_flow_style, canonical, indent, width, allow_unicode, line_break, encoding, explicit_start, explicit_end, version, tags)
    186     dumper.open()
    187     for data in documents:
--> 188         dumper.represent(data)
    189     dumper.close()
    190 finally:

File /usr/lib/python3/dist-packages/yaml/representer.py:26, in BaseRepresenter.represent(self, data)
     25 def represent(self, data):
---> 26     node = self.represent_data(data)
     27     self.serialize(node)
     28     self.represented_objects = {}

File /usr/lib/python3/dist-packages/yaml/representer.py:47, in BaseRepresenter.represent_data(self, data)
     45 data_types = type(data).__mro__
     46 if data_types[0] in self.yaml_representers:
---> 47     node = self.yaml_representers[data_types[0]](self, data)
     48 else:
     49     for data_type in data_types:

File /usr/lib/python3/dist-packages/yaml/representer.py:205, in SafeRepresenter.represent_dict(self, data)
    204 def represent_dict(self, data):
--> 205     return self.represent_mapping('tag:yaml.org,2002:map', data)

File /usr/lib/python3/dist-packages/yaml/representer.py:116, in BaseRepresenter.represent_mapping(self, tag, mapping, flow_style)
    114 for item_key, item_value in mapping:
    115     node_key = self.represent_data(item_key)
--> 116     node_value = self.represent_data(item_value)
    117     if not (isinstance(node_key, ScalarNode) and not node_key.style):
    118         best_style = False

File /usr/lib/python3/dist-packages/yaml/representer.py:51, in BaseRepresenter.represent_data(self, data)
     49 for data_type in data_types:
     50     if data_type in self.yaml_multi_representers:
---> 51         node = self.yaml_multi_representers[data_type](self, data)
     52         break
     53 else:

File /usr/lib/python3/dist-packages/yaml/representer.py:340, in Representer.represent_object(self, data)
    337 function_name = '%s.%s' % (function.__module__, function.__name__)
    338 if not args and not listitems and not dictitems \
    339         and isinstance(state, dict) and newobj:
--> 340     return self.represent_mapping(
    341             'tag:yaml.org,2002:python/object:'+function_name, state)
    342 if not listitems and not dictitems  \
    343         and isinstance(state, dict) and not state:
    344     return self.represent_sequence(tag+function_name, args)

File /usr/lib/python3/dist-packages/yaml/representer.py:116, in BaseRepresenter.represent_mapping(self, tag, mapping, flow_style)
    114 for item_key, item_value in mapping:
    115     node_key = self.represent_data(item_key)
--> 116     node_value = self.represent_data(item_value)
    117     if not (isinstance(node_key, ScalarNode) and not node_key.style):
    118         best_style = False

File /usr/lib/python3/dist-packages/yaml/representer.py:51, in BaseRepresenter.represent_data(self, data)
     49 for data_type in data_types:
     50     if data_type in self.yaml_multi_representers:
---> 51         node = self.yaml_multi_representers[data_type](self, data)
...
--> 315     reduce = data.__reduce_ex__(2)
    316 elif hasattr(data, '__reduce__'):
    317     reduce = data.__reduce__()

TypeError: cannot pickle 'weakref' object

System and version information

OS: Ubuntu 18.04 (WSL2 on Windows 10) Python: 3.8.13 hls4ml: 0.6.0