offer continuously parameterized time embedding for diffusion prior network, remove a hyperparameter that may trip up people, if not set correctly

README.md

@@ -34,7 +34,7 @@ Once built, images will be saved to the same directory the command is invoked
 
 To train DALLE-2 is a 3 step process, with the training of CLIP being the most important
 
-To train CLIP, you can either use `x-clip` package, or join the LAION discord, where a lot of replication efforts are already underway.
+To train CLIP, you can either use <a href="https://github.com/lucidrains/x-clip">x-clip</a> package, or join the LAION discord, where a lot of replication efforts are already underway.
 
 This repository will demonstrate integration with `x-clip` for starters
 
@@ -136,12 +136,14 @@ loss.backward()
 # then it will learn to generate images based on the CLIP image embeddings
 ```
 
-Finally, the main contribution of the paper. The repository offers the diffusion prior network. It takes the CLIP text embeddings and tries to generate the CLIP image embeddings. Again, you will need the trained CLIP fron the first step
+Finally, the main contribution of the paper. The repository offers the diffusion prior network. It takes the CLIP text embeddings and tries to generate the CLIP image embeddings. Again, you will need the trained CLIP from the first step
 
 ```python
 import torch
 from dalle2_pytorch import DiffusionPriorNetwork, DiffusionPrior, CLIP
 
+# get trained CLIP from step one
+
 clip = CLIP(
     dim_text = 512,
     dim_image = 512,
@@ -160,7 +162,6 @@ clip = CLIP(
 
 prior_network = DiffusionPriorNetwork(
     dim = 512,
-    num_timesteps = 100,
     depth = 6,
     dim_head = 64,
     heads = 8
@@ -249,7 +250,6 @@ loss.backward()
 
 prior_network = DiffusionPriorNetwork(
     dim = 512,
-    num_timesteps = 100,
     depth = 6,
     dim_head = 64,
     heads = 8
@@ -294,7 +294,10 @@ dalle2 = DALLE2(
     decoder = decoder
 )
 
-images = dalle2(['cute puppy chasing after a squirrel'])
+images = dalle2(
+    ['cute puppy chasing after a squirrel'],
+    cond_scale = 2. # classifier free guidance strength (> 1 would strengthen the condition)
+)
 
 # save your image
 ```
@@ -317,6 +320,7 @@ For the layperson, no worries, training will all be automated into a CLI tool, a
 - [ ] figure out all the current bag of tricks needed to make DDPMs great (starting with the blur trick mentioned in paper)
 - [ ] train on a toy task, offer in colab
 - [ ] add attention to unet - apply some personal tricks with efficient attention
+- [ ] figure out the big idea behind latent diffusion and what can be ported over
 
 ## Citations
 

dalle2_pytorch/dalle2_pytorch.py

@@ -7,6 +7,7 @@ import torch.nn.functional as F
 from torch import nn, einsum
 
 from einops import rearrange, repeat
+from einops.layers.torch import Rearrange
 from einops_exts import rearrange_many, repeat_many, check_shape
 from einops_exts.torch import EinopsToAndFrom
 
@@ -124,6 +125,43 @@ class PreNormResidual(nn.Module):
     def forward(self, x, **kwargs):
         return self.fn(self.norm(x), **kwargs) + x
 
+# mlp
+
+class MLP(nn.Module):
+    def __init__(
+        self,
+        dim_in,
+        dim_out,
+        *,
+        expansion_factor = 2.,
+        depth = 2,
+        norm = False,
+    ):
+        super().__init__()
+        hidden_dim = int(expansion_factor * dim_out)
+        norm_fn = lambda: nn.LayerNorm(hidden_dim) if norm else nn.Identity()
+
+        layers = [nn.Sequential(
+            nn.Linear(dim_in, hidden_dim),
+            nn.SiLU(),
+            norm_fn()
+        )]
+
+        for _ in range(depth - 1):
+            layers.append(nn.Sequential(
+                nn.Linear(hidden_dim, hidden_dim),
+                nn.SiLU(),
+                norm_fn()
+            ))
+
+        layers.append(nn.Linear(hidden_dim, dim_out))
+        self.net = nn.Sequential(*layers)
+
+    def forward(self, x):
+        return self.net(x.float())
+
+# feedforward
+
 def FeedForward(dim, mult = 4, dropout = 0.):
     inner_dim = int(mult * dim)
     return nn.Sequential(
@@ -134,6 +172,8 @@ def FeedForward(dim, mult = 4, dropout = 0.):
         nn.Linear(inner_dim, dim, bias = False)
     )
 
+# attention
+
 class Attention(nn.Module):
     def __init__(
         self,
@@ -235,26 +275,27 @@ class DiffusionPriorNetwork(nn.Module):
     def __init__(
         self,
         dim,
-        num_timesteps = 1000,
+        num_timesteps = None,
         **kwargs
     ):
         super().__init__()
-        self.time_embeddings = nn.Embedding(num_timesteps, dim)  # also offer a continuous version of timestep embeddings, with a 2 layer MLP
+        self.time_embeddings = nn.Embedding(num_timesteps, dim) if exists(num_timesteps) else nn.Sequential(Rearrange('b -> b 1'), MLP(1, dim)) # also offer a continuous version of timestep embeddings, with a 2 layer MLP
         self.learned_query = nn.Parameter(torch.randn(dim))
         self.causal_transformer = CausalTransformer(dim = dim, **kwargs)
 
     def forward_with_cond_scale(
         self,
         x,
-        *,
+        *args,
         cond_scale = 1.,
         **kwargs
     ):
-        if cond_scale == 1:
-            return self.forward(x, **kwargs)
+        logits = self.forward(x, *args, **kwargs)
 
-        logits = self.forward(x, **kwargs)
-        null_logits = self.forward(x, cond_drop_prob = 1., **kwargs)
+        if cond_scale == 1:
+            return logits
+
+        null_logits = self.forward(x, *args, cond_drop_prob = 1., **kwargs)
         return null_logits + (logits - null_logits) * cond_scale
 
     def forward(
@@ -635,15 +676,16 @@ class Unet(nn.Module):
     def forward_with_cond_scale(
         self,
         x,
-        *,
+        *args,
         cond_scale = 1.,
         **kwargs
     ):
-        if cond_scale == 1:
-            return self.forward(x, **kwargs)
+        logits = self.forward(x, *args, **kwargs)
 
-        logits = self.forward(x, **kwargs)
-        null_logits = self.forward(x, cond_drop_prob = 1., **kwargs)
+        if cond_scale == 1:
+            return logits
+
+        null_logits = self.forward(x, *args, cond_drop_prob = 1., **kwargs)
         return null_logits + (logits - null_logits) * cond_scale
 
     def forward(
@@ -774,8 +816,8 @@ class Decoder(nn.Module):
         posterior_log_variance_clipped = extract(self.posterior_log_variance_clipped, t, x_t.shape)
         return posterior_mean, posterior_variance, posterior_log_variance_clipped
 
-    def p_mean_variance(self, x, t, image_embed, clip_denoised: bool):
-        x_recon = self.predict_start_from_noise(x, t = t, noise = self.net(x, t, image_embed = image_embed))
+    def p_mean_variance(self, x, t, image_embed, clip_denoised = True, cond_scale = 1.):
+        x_recon = self.predict_start_from_noise(x, t = t, noise = self.net.forward_with_cond_scale(x, t, image_embed = image_embed, cond_scale = cond_scale))
 
         if clip_denoised:
             x_recon.clamp_(-1., 1.)
@@ -784,31 +826,31 @@ class Decoder(nn.Module):
         return model_mean, posterior_variance, posterior_log_variance
 
     @torch.no_grad()
-    def p_sample(self, x, t, image_embed, clip_denoised = True, repeat_noise = False):
+    def p_sample(self, x, t, image_embed, cond_scale = 1., clip_denoised = True, repeat_noise = False):
         b, *_, device = *x.shape, x.device
-        model_mean, _, model_log_variance = self.p_mean_variance(x = x, t = t, image_embed = image_embed, clip_denoised = clip_denoised)
+        model_mean, _, model_log_variance = self.p_mean_variance(x = x, t = t, image_embed = image_embed, cond_scale = cond_scale, clip_denoised = clip_denoised)
         noise = noise_like(x.shape, device, repeat_noise)
         # no noise when t == 0
         nonzero_mask = (1 - (t == 0).float()).reshape(b, *((1,) * (len(x.shape) - 1)))
         return model_mean + nonzero_mask * (0.5 * model_log_variance).exp() * noise
 
     @torch.no_grad()
-    def p_sample_loop(self, shape, image_embed):
+    def p_sample_loop(self, shape, image_embed, cond_scale = 1):
         device = self.betas.device
 
         b = shape[0]
         img = torch.randn(shape, device=device)
 
         for i in tqdm(reversed(range(0, self.num_timesteps)), desc='sampling loop time step', total=self.num_timesteps):
-            img = self.p_sample(img, torch.full((b,), i, device = device, dtype = torch.long), image_embed = image_embed)
+            img = self.p_sample(img, torch.full((b,), i, device = device, dtype = torch.long), image_embed = image_embed, cond_scale = cond_scale)
         return img
 
     @torch.no_grad()
-    def sample(self, image_embed):
+    def sample(self, image_embed, cond_scale = 1.):
         batch_size = image_embed.shape[0]
         image_size = self.image_size
         channels = self.channels
-        return self.p_sample_loop((batch_size, channels, image_size, image_size), image_embed = image_embed)
+        return self.p_sample_loop((batch_size, channels, image_size, image_size), image_embed = image_embed, cond_scale = cond_scale)
 
     def q_sample(self, x_start, t, noise=None):
         noise = default(noise, lambda: torch.randn_like(x_start))
@@ -869,7 +911,8 @@ class DALLE2(nn.Module):
     @torch.no_grad()
     def forward(
         self,
-        text
+        text,
+        cond_scale = 1.
     ):
         device = next(self.parameters()).device
 
@@ -878,5 +921,5 @@ class DALLE2(nn.Module):
             text = tokenizer.tokenize(text).to(device)
 
         image_embed = self.prior.sample(text, num_samples_per_batch = self.prior_num_samples)
-        images = self.decoder.sample(image_embed)
+        images = self.decoder.sample(image_embed, cond_scale = cond_scale)
         return images

setup.py

@@ -10,7 +10,7 @@ setup(
       'dream = dalle2_pytorch.cli:dream'
     ],
   },
-  version = '0.0.6',
+  version = '0.0.8',
   license='MIT',
   description = 'DALL-E 2',
   author = 'Phil Wang',