have researcher explicitly state upfront whether to condition with text encodings in cascading ddpm decoder, have DALLE-2 class take care of passing in text if feature turned on

dalle2_pytorch/dalle2_pytorch.py

@@ -894,6 +894,7 @@ class Unet(nn.Module):
         sparse_attn_window = 8,  # window size for sparse attention
         attend_at_middle = True, # whether to have a layer of attention at the bottleneck (can turn off for higher resolution in cascading DDPM, before bringing in efficient attention)
         cond_on_text_encodings = False,
+        max_text_len = 256,
         cond_on_image_embeds = False,
     ):
         super().__init__()
@@ -944,7 +945,7 @@ class Unet(nn.Module):
         # for classifier free guidance
 
         self.null_image_embed = nn.Parameter(torch.randn(1, num_image_tokens, cond_dim))
-        self.null_text_embed = nn.Parameter(torch.randn(1, 1, cond_dim))
+        self.null_text_embed = nn.Parameter(torch.randn(1, max_text_len, cond_dim))
 
         # attention related params
 
@@ -1072,7 +1073,7 @@ class Unet(nn.Module):
             text_tokens = torch.where(
                 cond_prob_mask,
                 text_tokens,
-                self.null_text_embed
+                self.null_text_embed[:, :text_tokens.shape[1]]
             )
 
         # main conditioning tokens (c)
@@ -1170,6 +1171,7 @@ class Decoder(nn.Module):
         lowres_downsample_first = True,             # cascading ddpm - resizes to lower resolution, then to next conditional resolution + blur
         blur_sigma = 0.1,                           # cascading ddpm - blur sigma
         blur_kernel_size = 3,                       # cascading ddpm - blur kernel size
+        condition_on_text_encodings = False,        # the paper suggested that this didn't do much in the decoder, but i'm allowing the option for experimentation
     ):
         super().__init__()
         assert isinstance(clip, CLIP)
@@ -1178,6 +1180,8 @@ class Decoder(nn.Module):
         self.clip_image_size = clip.image_size
         self.channels = clip.image_channels
 
+        self.condition_on_text_encodings = condition_on_text_encodings
+
         # automatically take care of ensuring that first unet is unconditional
         # while the rest of the unets are conditioned on the low resolution image produced by previous unet
 
@@ -1421,6 +1425,8 @@ class Decoder(nn.Module):
 
         text_encodings = self.get_text_encodings(text) if exists(text) else None
 
+        assert not (self.condition_on_text_encodings and not exists(text_encodings)), 'text or text encodings must be passed into decoder if specified'
+
         img = None
 
         for unet, vae, channel, image_size, predict_x_start in tqdm(zip(self.unets, self.vaes, self.sample_channels, self.image_sizes, self.predict_x_start)):
@@ -1481,6 +1487,8 @@ class Decoder(nn.Module):
 
         text_encodings = self.get_text_encodings(text) if exists(text) and not exists(text_encodings) else None
 
+        assert not (self.condition_on_text_encodings and not exists(text_encodings)), 'text or text encodings must be passed into decoder if specified'
+
         lowres_cond_img = self.to_lowres_cond(image, target_image_size = target_image_size, downsample_image_size = self.image_sizes[unet_index - 1]) if unet_number > 1 else None
         image = resize_image_to(image, target_image_size)
 
@@ -1508,7 +1516,9 @@ class DALLE2(nn.Module):
         assert isinstance(decoder, Decoder)
         self.prior = prior
         self.decoder = decoder
+
         self.prior_num_samples = prior_num_samples
+        self.decoder_need_text_cond = self.decoder.condition_on_text_encodings
 
     @torch.no_grad()
     @eval_decorator
@@ -1525,7 +1535,9 @@ 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, cond_scale = cond_scale)
+
+        text_cond = text if self.decoder_need_text_cond else None
+        images = self.decoder.sample(image_embed, text = text_cond, cond_scale = cond_scale)
 
         if one_text:
             return images[0]