[RMP] Support for simple ML/CF Models (like Implicit) in Merlin Models and Systems

Problem:

Latent factor models enable discovery of the underlying structure between interactions and items. These approaches have been popular over the years to leverage implicit feedback data. Customers who are using simple models via Implicit and LightFM want to be able to deploy those models within the Merlin ecosystem.

Goal:

• Provide training support for implicit and lightfm based models in Merlin Models
• Provide inference support for implicit based models in Merlin Systems
• NVIDIA-Merlin/systems#200

Constraints:

Systems

• Serve Implicit/LightFM as a self-contained op with everything required to serve within the exported triton model directory
  Requires installing the python package in the tritonserver environment where it will run.
  Decomposing the serving of these into different operators (retrieval with nearest neighbour search through embedding space)

Blocking issues

• Inference is blocked w/ issues on serialization of model w/ Implicit

Starting Point:

Merlin-models

wrap Implicit and lightFM in High-level model API:

• https://github.com/NVIDIA-Merlin/models/pull/218
• https://github.com/NVIDIA-Merlin/models/pull/219
  Note: 218 and 219 only builds the models. It doesn't take care of serving. It doesn't have the example.
• https://github.com/NVIDIA-Merlin/models/issues/410
  Note: Scope currently unclear (@oliverholworthy )

NVTabular

N/A

Merlin-systems

• NVIDIA-Merlin/systems#35
  • Implicit operator (self-contained)
    https://github.com/NVIDIA-Merlin/systems/pull/134
  • NVIDIA-Merlin/Merlin#457

Examples and Docs (To happen in 22.09)

• https://github.com/NVIDIA-Merlin/models/issues/561
• NVIDIA-Merlin/models#577
• NVIDIA-Merlin/models#576
• NVIDIA-Merlin/models#578