Registry¶

In DI-engine, in order to start a training task through config file convenientely, we recommend that you should utilize Registry mechanism to register those modules that are implemented by yourself.

For now, Registry supports these modules:

policy

env

model

reward_model

learner

buffer

serial_collector

parallel_collector

comm_learner

comm_collector

commander

league

player

Then we will take Policy to exemplify how to use Registry when you implement a new policy.

Add the Registry decorator for the new policy.

from ding.utils import POLICY_REGISTRY

@POLICY_REGISTRY.register('dqn')
class DQNPolicy(Policy):
    pass

In config file, list the name and file path of the new policy

In key type，write the name of the policy。

In key import_names，write the file path. import_names is asked to be a list, and each of its element is a python import abstract path(i.e. We can run import name1.name2 in Python Idle), such as:

ding.policy.dqn

dizoo.atari.envs.atari_env

The config file example is as follows:
create_config = dict(
    policy=dict(
        type='multi_head_dqn',
        import_names=['dizoo.common.policy.multi_head_dqn'],
    # ...
    )
)
If you carefully read the source code, you will find out that for polices implemented in DI-engine core code(in path ding/ding/), the import_names is not listed in config file. However, if you implement a new policy, it is a must to list import_names.

Create the module through system functions

If you want to start the training task through DI-engine serial_pipeline, for example, use CLI ding -m XXX -c XXXX_config.py -s XX, or call serial_pipeline function. Step 3 can be ignored, because serial_pipeline has already been done in serial_pipeline function. However, if you want to write your own pipeline, you can call create_policy function to create your policy.
```
from ding.policy import create_policy

cfg: dict
dqn_policy = create_policy(cfg.policy)
```

Besides, you can use CLI ding -q <registry name> to look up the modules that are already registered in DI-engine core code. For example：