[RFC] TVM Target Specification

Development pre-RFC
57

Follow up on my previous PR on supporting the new target system with target_host folded into the target object. I have submitted a new PR on review [Target] Add support for target object with host field compatible with previous api by zxybazh · Pull Request #7534 · apache/tvm · GitHub this week to fully support all functions previously using target and target_host as argument with backward compatibility. This PR’s scope is to cover everything before we finally deprecate target_host. New tutorial code and test code are also updated in the PR for recommended practice. Please review the code the let me know any advice on the PR, thanks!

Currently, I did not remove all usage of target_host as a variable mainly because of two reasons:

  1. For heterogeneous targets, there could be multiple targets maintained in a dict, which makes a single target_host more convenient in related context. If we decide to move on in the deprecation, we might need to consider refactor the code for heterogenoues target.
  2. It takes more time to replace all the occurance, and part of the code would be refactored, e.g., the structure of SearchTaskNode and the signature of target_host related functions, once we decide to deprecate target_host. I want to leave the work later if we decide on deprecation and be more consistent in design at that time.

In the meantime, for next step, as @comaniac pointed out in his comment [Target] Add support for target object with host field compatible with previous api by zxybazh · Pull Request #7534 · apache/tvm · GitHub we have different options in target_host deprecation (also see @junrushao [Target] Add target host field for target specification by zxybazh · Pull Request #7462 · apache/tvm · GitHub).

  • D0. Simply remove the target_host argument if that API is seldomly used.
  • D1. Keep the target_host argument, but log out a warning saying this is not effective anymore and will be deprecated. We can move on deprecation in the next release cycle.

I think both ways could work. Would like to see how does everyone think and which way could be better.