Covid_19_DINN/src/problem.py

import torch
from .dataset import PandemicDataset

class PandemicProblem:
    def __init__(self, data: PandemicDataset) -> None:
        """Parent class for all pandemic problem classes. Holding the function, that calculates the residuals of the differential system.

        Args:
            data (PandemicDataset): Dataset holding the time values used.
        """

        self._data = data
        self._device_name = data.device_name

        self._gradients = None

    def residual(self):
        """NEEDS TO BE IMPLEMENTED WHEN INHERITING FROM THIS CLASS
        """
        assert self._gradients != None, 'Gradientmatrix need to be defined'
        

    def def_grad_matrix(self, number:int):
        assert self._gradients == None, 'Gradientmatrix is already defined'
        self._gradients = [torch.zeros((len(self._data.t_raw), number), device=self._device_name) for _ in range(number)]
        for i in range(number):
            self._gradients[i][:, i] = 1

class SIRProblem(PandemicProblem):
    def __init__(self, data: PandemicDataset):
        super().__init__(data)

    def residual(self, SIR_pred, alpha, beta):
        super().residual()
        SIR_pred.backward(self._gradients[0], retain_graph=True)
        dSdt = self._data.t_raw.grad.clone()
        self._data.t_raw.grad.zero_()

        SIR_pred.backward(self._gradients[1], retain_graph=True)
        dIdt = self._data.t_raw.grad.clone()
        self._data.t_raw.grad.zero_()

        SIR_pred.backward(self._gradients[2], retain_graph=True)
        dRdt = self._data.t_raw.grad.clone()
        self._data.t_raw.grad.zero_()

        S, I, _ = self._data.get_denormalized_data([SIR_pred[:, 0], SIR_pred[:, 1], SIR_pred[:, 2]])

        S_residual = dSdt - (-beta * ((S * I) / self._data.N)) / (self._data.get_max('S') - self._data.get_min('S'))
        I_residual = dIdt - (beta * ((S * I) / self._data.N) - alpha * I) / (self._data.get_max('I') - self._data.get_min('I'))
        R_residual = dRdt - (alpha * I) / (self._data.get_max('R') - self._data.get_min('R'))

        return S_residual, I_residual, R_residual


class ReducedSIRProblem(PandemicProblem):
    def __init__(self, data: PandemicDataset, alpha:float):
        super().__init__(data)
        self.alpha = alpha

    def residual(self, SI_pred):
        super().residual()

        SI_pred.backward(self._gradients[0], retain_graph=True)
        dIdt = self._data.t_raw.grad.clone()
        self._data.t_raw.grad.zero_()
        
        I = SI_pred[:, 0]
        R_t = SI_pred[:, 1]

        I_residual = dIdt - (self.alpha * (self._data.t_final - self._data.t_init) * (R_t - 1) * I)

        return I_residual