Making a deep copy of an OPF model

Engineering NAB
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1

Hello!

I have an instance of an OPF model (the same one used in the numenta detector in NAB, actually) that I’d like to make a deep copy of in my code. The simplest solution (trying “model_copy = copy.deepcopy(model)”) does not work. When trying to do model_copy.run(), it breaks because self.__restoringFromState gets set to true inside model_copy which doesn’t pass an assert statement.

Could somebody explain or point me in the direction of documentation which explains how to make deep copies of models?

Best,
Brody

2

You probably want to use the old way of saving, which pickles things.

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3

Interesting…is there a new way of saving/loading models that is under development? Is that why it’s deprecated?

4

Yes, see the rest of the doc I sent. But to use this method you need to get hold of the algorithm instances.

5

Thanks for the quick responses…I have to create and load many copies and unfortunately writing to the file system is exceedingly slow. I’m going to keep trying to deep copy a model all within memory.

6

I notice the eq method is not overwritten in the base model class or the htm_prediction_model. Is there any code out there to test equality between two model instances?

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I’ll have to defer to @scott on that question.

8

I think you can probably use the new or old serialization completely in memory. The old method requires separate steps for the Python state (pickle) and C++ state so the new method is probably easier (and faster).

For the new method, you can see how to do an in-memory copy here:

It might be faster to use to_bytes_packed and from_bytes_packed instead of the unpacked version used in the example code. See pycapnp reference here:
http://jparyani.github.io/pycapnp/capnp.html#capnp._DynamicStructBuilder.to_bytes_packed
http://jparyani.github.io/pycapnp/capnp.html#capnp._StructModule.from_bytes_packed

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9

And you probably want to save the result of builderProto.to_bytes() into a variable that you can call from_bytes on multiple times to create multiple copies of the model.

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Excellent. You’re right, that method is much faster. For determining equality I’m just checking that they are giving the same output over time which is the case. Thanks so much for your help.

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