[Bug] NotImplementedError when using env.fork() with SynchronousSqliteLogger

[ricardoprins]

The code below was executed from a Google Colab Notebook:

db_path = Path("/content/db/test.db")

env = SynchronousSqliteLogger(
    env=gym.make('llvm-ir-ic-v0'),
    db_path=db_path,
)

from time import time

def greedy(env, search_time_seconds: int, **kwargs) -> None:

    def eval_action(env, action: int):
        with env.fork() as fkd:
            return (fkd.step(action)[1], action)

    end_time = time() + search_time_seconds
    while time() < end_time:
        best = max(eval_action(env, action) for action in range(env.action_space.n))
        if best[0] <= 0 or env.step(best[1])[2]:
            return

greedy(env, 300)

and here's the traceback:

---------------------------------------------------------------------------

NotImplementedError                       Traceback (most recent call last)

[<ipython-input-3-5160ef3145bf>](https://localhost:8080/#) in <module>()
     21             return
     22 
---> 23 greedy(env, 300)

3 frames

[<ipython-input-3-5160ef3145bf>](https://localhost:8080/#) in greedy(env, search_time_seconds, **kwargs)
     17     end_time = time() + search_time_seconds
     18     while time() < end_time:
---> 19         best = max(eval_action(env, action) for action in range(env.action_space.n))
     20         if best[0] <= 0 or env.step(best[1])[2]:
     21             return

[<ipython-input-3-5160ef3145bf>](https://localhost:8080/#) in <genexpr>(.0)
     17     end_time = time() + search_time_seconds
     18     while time() < end_time:
---> 19         best = max(eval_action(env, action) for action in range(env.action_space.n))
     20         if best[0] <= 0 or env.step(best[1])[2]:
     21             return

[<ipython-input-3-5160ef3145bf>](https://localhost:8080/#) in eval_action(env, action)
     12 
     13     def eval_action(env, action: int):
---> 14         with env.fork() as fkd:
     15             return (fkd.step(action)[1], action)
     16 

[/usr/local/lib/python3.7/dist-packages/compiler_gym/wrappers/sqlite_logger.py](https://localhost:8080/#) in fork(self)
    272 
    273     def fork(self):
--> 274         raise NotImplementedError

NotImplementedError:

[ChrisCummins]

Thanks for the report @ricardoprins. I can see that the problem is the SqliteLogger does not yet support fork():

https://github.com/facebookresearch/CompilerGym/blob/development/compiler_gym/wrappers/sqlite_logger.py#L273-L274

Would you like to have a go at implementing it?

Cheers, Chris

[ricardoprins]

Sure, I'll try!

[ricardoprins]

Would simply doing this work, or are there any problems I'm unaware of?

The fork() method is already implemented in the CompilerEnvWrapper class, which the logger inherits from.

    def fork(self):
        return super().fork()

[ChrisCummins]

Would simply doing this work, or are there any problems I'm unaware of?

The fork() method is already implemented in the CompilerEnvWrapper class, which the logger inherits from.

    def fork(self):
        return super().fork()

Not quite. You would need to make sure to construct a new SliteLoggerWrapper class and pass in the right constructor arguments so that the forked environment writes to the same database.

Cheers, Chris