CNTK model format

CNTK allows users to save a model into a file for future use. It can be done by

• specifying "modelPath" in the config file when using BrainScript/cntk.exe, or
• save_model() in python, or
• SaveModel() in C++ when using CNTK Library API.

There are two different file formats to store the model in.

• The model-v1 format. This format was originally used prior to the CNTK2 version. A model is stored in the model-v1 format when it is saved

  • by BrainScript/cntk.exe, or
  • by save_model() in python, when the parameter use_legacy_format is true (default value), or
  • by SaveModel() in C++, when the parameter useLegacyModelFormat is true (default value).

• The model-v2 format. With CNTK2, a Protobuf based format is introduced, which is now known as the model-v2 format. A model is saved in this format only when using CNTK Library API

  • by save_model() in python, when the parameter use_legacy_format is false, or
  • by SaveModel() in C++, when the parameter useLegacyModelFormat is false.

The following table gives an overview about which model format is created and consumed by which CNTK binary.

	Model Creation	Model Evaluation	Lanugage Support
model-v1 format	cntk.exe; CNTK Library	EvalDll, CNTK Library	BrainScript, C++, C#
model-v2 format	CNTK Library	CNTK Library	C++, Python