Pass filename components into Checkpoint.load_objects

[KevinMusgrave]

🚀 Feature

Currently, objects can be loaded like this:

from ignite.handlers import Checkpoint

Checkpoint.load_objects(to_load=to_load, checkpoint=checkpoint_fp)

It would be nice to have the following as an option:

from ignite.handlers import Checkpoint

checkpointer = Checkpoint(...)
checkpointer.load_objects(to_load=to_load, filename_components={"name": name, "global_step": global_step})

In other words, pass in components of self.filename_pattern. The Checkpoint object already has self.filename_pattern, self.filename_prefix, self.ext, and it should also have the dirname that is passed into __init__. So most of the components of constructing the filename are already defined in the Checkpoint object. Getting the user to recreate the full file path is unnecessary.

[vfdev-5]

@KevinMusgrave interesting feature request. What is "name" in your example ?
So, you would like to see an instance method (today we have a static method) load_objects that could reuse previous info to recreate filepath using a dictionary ?

# for example
filepath = self.dirname / (f"{self.filename_prefix}_{name}_{global_step}.{self.ext}")

[KevinMusgrave]

Yes, basically I don't want to have to copy-paste this snippet into my own code (plus doing os.path.join(dirname, ...):

ignite/ignite/handlers/checkpoint.py

Lines 403 to 411 in c202a9a

	filename_dict = {
	"filename_prefix": self.filename_prefix,
	"ext": self.ext,
	"name": name,
	"score_name": self.score_name,
	"score": priority_str if (self.score_function is not None) else None,
	"global_step": global_step,
	}
	filename = filename_pattern.format(**filename_dict)

[vfdev-5]

I see, that makes sense. Let me see what can be done for that.

[sdesrozis]

A quick and dirty implementation could be the following (to be inserted in the Checkpoint class)

def reload_objects(self, to_load: Mapping, filename_components: dict, **kwargs: Any) -> None:
            
    global_step = filename_components.get("global_step", None)

    if self.filename_pattern is None:
        filename_pattern = self.setup_filename_pattern(
            with_prefix=len(self.filename_prefix) > 0,
            with_score=self.score_function is not None,
            with_score_name=self.score_name is not None,
            with_global_step=global_step is not None,
        )
    else:
        filename_pattern = self.filename_pattern

    name = filename_components.get("name", "checkpoint")
    score = filename_components.get("score", None)

     filename_dict = {
        "filename_prefix": self.filename_prefix,
        "ext": self.ext,
        "name": name,
        "score_name": self.score_name,
        "score": score,
        "global_step": global_step,
    }
        
    checkpoint_fp = filename_pattern.format(**filename_dict)

    path = self.save_handler.dirname / checkpoint_fp 

    Checkpoint.load_objects(to_load=to_load, checkpoint=str(path), **kwargs)

@KevinMusgrave does it sound good to you or I missed the point ?

[KevinMusgrave]

Looks good to me!

[sdesrozis]

@vfdev-5 Interested by your feedback, I will submit a PR afterwards.

[vfdev-5]

@sdesrozis looks good to me as well. I was also wondering if we could make the method signature as

def reload_objects(self, to_load: Mapping, **filename_components, load_kwards: Optional[Dict] = None) -> None:

basically, fetching filename_components as kwargs and rarely used load_kwards as a dict