from jittor import Module
from typing import List, Callable, Dict
from ..higher_jit.patch import _MonkeyPatchBase
from jboat.operation_registry import register_class
from jboat.na_ol.hyper_gradient import HyperGradient
[docs]
@register_class
class PTT(HyperGradient):
"""
Computes the hyper-gradient of the upper-level variables using Pessimistic Trajectory Truncation (PTT) [1].
Parameters
----------
ll_objective : Callable
The lower-level objective function of the BLO problem.
ul_objective : Callable
The upper-level objective function of the BLO problem.
ll_model : jittor.Module
The lower-level model of the BLO problem.
ul_model : jittor.Module
The upper-level model of the BLO problem.
ll_var : List[jittor.Var]
List of variables optimized with the lower-level objective.
ul_var : List[jittor.Var]
List of variables optimized with the upper-level objective.
solver_config : Dict[str, Any]
Dictionary containing solver configurations, including:
- "na_op" (List[str]): Indicates if PTT is used in the hyper-gradient operations.
References
----------
[1] Liu R., Liu Y., Zeng S., et al. "Towards gradient-based bilevel optimization with non-convex followers and beyond," in NeurIPS, 2021.
"""
def __init__(
self,
ll_objective: Callable,
ul_objective: Callable,
ll_model: Module,
ul_model: Module,
ll_var: List,
ul_var: List,
solver_config: Dict,
):
super(PTT, self).__init__(
ll_objective,
ul_objective,
ul_model,
ll_model,
ll_var,
ul_var,
solver_config,
)
self.truncate_max_loss_iter = "PTT" in solver_config["na_op"]
[docs]
def compute_gradients(
self,
ll_feed_dict: Dict,
ul_feed_dict: Dict,
auxiliary_model: _MonkeyPatchBase,
max_loss_iter: int = 0,
hyper_gradient_finished: bool = False,
next_operation: str = None,
**kwargs
):
"""
Compute the hyper-gradients of the upper-level variables with the data from feed_dict and patched models.
Parameters
----------
ll_feed_dict : Dict
Dictionary containing the lower-level data used for optimization.
It typically includes training data, targets, and other information required to compute the LL objective.
ul_feed_dict : Dict
Dictionary containing the upper-level data used for optimization.
It typically includes validation data, targets, and other information required to compute the UL objective.
auxiliary_model : _MonkeyPatchBase
A patched lower model wrapped by the `higher` library.
It serves as the lower-level model for optimization.
max_loss_iter : int, optional
The number of iterations used for backpropagation, by default 0.
next_operation : str, optional
The next operator for the calculation of the hypergradient, by default None.
hyper_gradient_finished : bool, optional
A boolean flag indicating whether the hypergradient computation is finished, by default False.
Returns
-------
Dict
A dictionary containing updated feed_dict, auxiliary model, and gradient computation results.
"""
assert (
hyper_gradient_finished is False
), "Hypergradient computation should not be finished"
assert self.truncate_max_loss_iter and (
max_loss_iter > 0
), "With PTT operation, 'max_loss_iter' should be greater than 0"
assert next_operation is not None, "Next operation should be defined"
lower_model_params = kwargs.get(
"lower_model_params", list(auxiliary_model.parameters(time=max_loss_iter))
)
return {
"ll_feed_dict": ll_feed_dict,
"ul_feed_dict": ul_feed_dict,
"auxiliary_model": auxiliary_model,
"max_loss_iter": max_loss_iter,
"hyper_gradient_finished": False,
"lower_model_params": lower_model_params,
**kwargs,
}