Constrain and unconstrain

constrain.py

import torch


def constrain(x, min, max, temperature:float=1.):
    return (max - min) * torch.sigmoid(x / temperature) + min

def unconstrain(y, min, max, temperature:float=1, EPS:float=1e-8):
    assert torch.all(y >= min) and torch.all(y <= max)
    # ensure both numerator and denominator are positive
    numerator = y - min 
    denominator = max - min
    return temperature * torch.logit(numerator / denominator, eps=EPS)