Source code for pina.callbacks.adaptive_refinment_callbacks

"""PINA Callbacks Implementations"""

import torch
from pytorch_lightning.callbacks import Callback
from ..label_tensor import LabelTensor
from ..utils import check_consistency


[docs] class R3Refinement(Callback): def __init__(self, sample_every): """ PINA Implementation of an R3 Refinement Callback. This callback implements the R3 (Retain-Resample-Release) routine for sampling new points based on adaptive search. The algorithm incrementally accumulates collocation points in regions of high PDE residuals, and releases those with low residuals. Points are sampled uniformly in all regions where sampling is needed. .. seealso:: Original Reference: Daw, Arka, et al. *Mitigating Propagation Failures in Physics-informed Neural Networks using Retain-Resample-Release (R3) Sampling. (2023)*. DOI: `10.48550/arXiv.2207.02338 <https://doi.org/10.48550/arXiv.2207.02338>`_ :param int sample_every: Frequency for sampling. :raises ValueError: If `sample_every` is not an integer. Example: >>> r3_callback = R3Refinement(sample_every=5) """ super().__init__() # sample every check_consistency(sample_every, int) self._sample_every = sample_every self._const_pts = None def _compute_residual(self, trainer): """ Computes the residuals for a PINN object. :return: the total loss, and pointwise loss. :rtype: tuple """ # extract the solver and device from trainer solver = trainer._model device = trainer._accelerator_connector._accelerator_flag precision = trainer.precision if precision == "64-true": precision = torch.float64 elif precision == "32-true": precision = torch.float32 else: raise RuntimeError( "Currently R3Refinement is only implemented " "for precision '32-true' and '64-true', set " "Trainer precision to match one of the " "available precisions." ) # compute residual res_loss = {} tot_loss = [] for location in self._sampling_locations: condition = solver.problem.conditions[location] pts = solver.problem.input_pts[location] # send points to correct device pts = pts.to(device=device, dtype=precision) pts = pts.requires_grad_(True) pts.retain_grad() # PINN loss: equation evaluated only for sampling locations target = condition.equation.residual(pts, solver.forward(pts)) res_loss[location] = torch.abs(target).as_subclass(torch.Tensor) tot_loss.append(torch.abs(target)) return torch.vstack(tot_loss), res_loss def _r3_routine(self, trainer): """ R3 refinement main routine. :param Trainer trainer: PINA Trainer. """ # compute residual (all device possible) tot_loss, res_loss = self._compute_residual(trainer) tot_loss = tot_loss.as_subclass(torch.Tensor) # !!!!!! From now everything is performed on CPU !!!!!! # average loss avg = (tot_loss.mean()).to("cpu") old_pts = {} # points to be retained for location in self._sampling_locations: pts = trainer._model.problem.input_pts[location] labels = pts.labels pts = pts.cpu().detach().as_subclass(torch.Tensor) residuals = res_loss[location].cpu() mask = (residuals > avg).flatten() if any(mask): # append residuals greater than average pts = (pts[mask]).as_subclass(LabelTensor) pts.labels = labels old_pts[location] = pts numb_pts = self._const_pts[location] - len(old_pts[location]) # sample new points trainer._model.problem.discretise_domain( numb_pts, "random", locations=[location] ) else: # if no res greater than average, samples all uniformly numb_pts = self._const_pts[location] # sample new points trainer._model.problem.discretise_domain( numb_pts, "random", locations=[location] ) # adding previous population points trainer._model.problem.add_points(old_pts) # update dataloader trainer._create_or_update_loader()
[docs] def on_train_start(self, trainer, _): """ Callback function called at the start of training. This method extracts the locations for sampling from the problem conditions and calculates the total population. :param trainer: The trainer object managing the training process. :type trainer: pytorch_lightning.Trainer :param _: Placeholder argument (not used). :return: None :rtype: None """ # extract locations for sampling problem = trainer._model.problem locations = [] for condition_name in problem.conditions: condition = problem.conditions[condition_name] if hasattr(condition, "location"): locations.append(condition_name) self._sampling_locations = locations # extract total population const_pts = {} # for each location, store the # of pts to keep constant for location in self._sampling_locations: pts = trainer._model.problem.input_pts[location] const_pts[location] = len(pts) self._const_pts = const_pts
[docs] def on_train_epoch_end(self, trainer, __): """ Callback function called at the end of each training epoch. This method triggers the R3 routine for refinement if the current epoch is a multiple of `_sample_every`. :param trainer: The trainer object managing the training process. :type trainer: pytorch_lightning.Trainer :param __: Placeholder argument (not used). :return: None :rtype: None """ if trainer.current_epoch % self._sample_every == 0: self._r3_routine(trainer)