source/model.py

from __future__ import annotations

import torch
from torch import nn


class LiquidTimeConstantRNN(nn.Module):
    def __init__(self, hidden_dimensions: int = 41) -> None:
        super().__init__()
        self.hidden_dimensions = hidden_dimensions
        self.candidate = nn.Linear(hidden_dimensions + 2, hidden_dimensions)
        self.log_time_constant = nn.Parameter(torch.zeros(hidden_dimensions))
        self.output = nn.Linear(hidden_dimensions, 1)

    def forward(self, sequence: torch.Tensor) -> torch.Tensor:
        hidden = torch.zeros(
            len(sequence),
            self.hidden_dimensions,
            device=sequence.device,
        )
        time_constant = torch.nn.functional.softplus(self.log_time_constant) + 0.03
        outputs = []
        for step in range(sequence.shape[1]):
            value_and_dt = sequence[:, step]
            candidate_inputs = torch.cat(
                [
                    value_and_dt[:, :1],
                    value_and_dt[:, 1:2].clamp(max=0.12),
                ],
                dim=1,
            )
            candidate = torch.tanh(
                self.candidate(torch.cat([candidate_inputs, hidden], dim=1))
            )
            delta_time = value_and_dt[:, 1:2]
            decay = torch.exp(-delta_time / time_constant[None])
            hidden = decay * hidden + (1 - decay) * candidate
            outputs.append(self.output(hidden))
        return torch.stack(outputs, dim=1)


class MatchedGRU(nn.Module):
    def __init__(self, hidden_dimensions: int = 23) -> None:
        super().__init__()
        self.recurrent = nn.GRU(2, hidden_dimensions, batch_first=True)
        self.output = nn.Linear(hidden_dimensions, 1)

    def forward(self, sequence: torch.Tensor) -> torch.Tensor:
        hidden, _ = self.recurrent(sequence)
        return self.output(hidden)


class MatchedRNN(nn.Module):
    def __init__(self, hidden_dimensions: int = 41) -> None:
        super().__init__()
        self.recurrent = nn.RNN(2, hidden_dimensions, batch_first=True)
        self.output = nn.Linear(hidden_dimensions, 1)

    def forward(self, sequence: torch.Tensor) -> torch.Tensor:
        hidden, _ = self.recurrent(sequence)
        return self.output(hidden)


def parameter_count(model: nn.Module) -> int:
    return sum(parameter.numel() for parameter in model.parameters())