diff --git a/denoising_diffusion_pytorch/__init__.py b/denoising_diffusion_pytorch/__init__.py index 7831cbe..5082fd7 100644 --- a/denoising_diffusion_pytorch/__init__.py +++ b/denoising_diffusion_pytorch/__init__.py @@ -1,2 +1,4 @@ from denoising_diffusion_pytorch.denoising_diffusion_pytorch import GaussianDiffusion, Unet, Trainer + from denoising_diffusion_pytorch.learned_gaussian_diffusion import LearnedGaussianDiffusion +from denoising_diffusion_pytorch.weighted_objective_gaussian_diffusion import WeightedObjectiveGaussianDiffusion diff --git a/denoising_diffusion_pytorch/weighted_objective_gaussian_diffusion.py b/denoising_diffusion_pytorch/weighted_objective_gaussian_diffusion.py new file mode 100644 index 0000000..a92e833 --- /dev/null +++ b/denoising_diffusion_pytorch/weighted_objective_gaussian_diffusion.py @@ -0,0 +1,80 @@ +import torch +from inspect import isfunction +from torch import nn, einsum +from einops import rearrange + +from denoising_diffusion_pytorch.denoising_diffusion_pytorch import GaussianDiffusion, extract, unnormalize_to_zero_to_one + +# helper functions + +def exists(x): + return x is not None + +def default(val, d): + if exists(val): + return val + return d() if isfunction(d) else d + +# some improvisation on my end +# where i have the model learn to both predict noise and x0 +# and learn the weighted sum for each depending on time step + +class WeightedObjectiveGaussianDiffusion(GaussianDiffusion): + def __init__( + self, + denoise_fn, + *args, + pred_noise_loss_weight = 0.1, + pred_x_start_loss_weight = 0.1, + **kwargs + ): + super().__init__(denoise_fn, *args, **kwargs) + channels = denoise_fn.channels + assert denoise_fn.out_dim == (channels * 2 + 2), 'dimension out (out_dim) of unet must be twice the number of channels + 2 (for the softmax weighted sum) - for channels of 3, this should be (3 * 2) + 2 = 8' + + self.split_dims = (channels, channels, 2) + self.pred_noise_loss_weight = pred_noise_loss_weight + self.pred_x_start_loss_weight = pred_x_start_loss_weight + + def p_mean_variance(self, *, x, t, clip_denoised, model_output = None): + model_output = self.denoise_fn(x, t) + + pred_noise, pred_x_start, weights = model_output.split(self.split_dims, dim = 1) + normalized_weights = weights.softmax(dim = 1) + + x_start_from_noise = self.predict_start_from_noise(x, t = t, noise = pred_noise) + + x_starts = torch.stack((x_start_from_noise, pred_x_start), dim = 1) + weighted_x_start = einsum('b j h w, b j c h w -> b c h w', normalized_weights, x_starts) + + if clip_denoised: + weighted_x_start.clamp_(-1., 1.) + + model_mean, model_variance, model_log_variance = self.q_posterior(weighted_x_start, x, t) + + return model_mean, model_variance, model_log_variance + + def p_losses(self, x_start, t, noise = None, clip_denoised = False): + noise = default(noise, lambda: torch.randn_like(x_start)) + x_t = self.q_sample(x_start = x_start, t = t, noise = noise) + + model_output = self.denoise_fn(x_t, t) + pred_noise, pred_x_start, weights = model_output.split(self.split_dims, dim = 1) + + # get loss for predicted noise and x_start + # with the loss weight given at initialization + + noise_loss = self.loss_fn(noise, pred_noise) * self.pred_noise_loss_weight + x_start_loss = self.loss_fn(x_start, pred_x_start) * self.pred_x_start_loss_weight + + # calculate x_start from predicted noise + # then do a weighted sum of the x_start prediction, weights also predicted by the model (softmax normalized) + + x_start_from_pred_noise = self.predict_start_from_noise(x_t, t, pred_noise) + x_start_from_pred_noise = x_start_from_pred_noise.clamp(-2., 2.) + weighted_x_start = einsum('b j h w, b j c h w -> b c h w', weights.softmax(dim = 1), torch.stack((x_start_from_pred_noise, pred_x_start), dim = 1)) + + # main loss to x_start with the weighted one + + weighted_x_start_loss = self.loss_fn(x_start, weighted_x_start) + return weighted_x_start_loss + x_start_loss + noise_loss diff --git a/setup.py b/setup.py index a08ff22..0b421ee 100644 --- a/setup.py +++ b/setup.py @@ -3,7 +3,7 @@ from setuptools import setup, find_packages setup( name = 'denoising-diffusion-pytorch', packages = find_packages(), - version = '0.15.0', + version = '0.15.1', license='MIT', description = 'Denoising Diffusion Probabilistic Models - Pytorch', author = 'Phil Wang',