add shift to schedule

main.py

@@ -12,9 +12,10 @@ image = flux.generate_image(
     seed=3,
     prompt="Luxury food photograph of a birthday cake. In the middle it has three candles shaped like letters spelling the word 'MLX'. It has perfect lighting and a cozy background with big bokeh and shallow depth of field. The mood is a sunset balcony in tuscany. The photo is taken from the side of the cake. The scene is complemented by a warm, inviting light that highlights the textures and colors of the ingredients, giving it an appetizing and elegant look.",
     config=Config(
-        num_inference_steps=2,
+        num_inference_steps=20,
         width=256,
         height=256,
+        guidance=3.5,
     )
 )
 

src/flux_1_schnell/config/config.py

@@ -13,18 +13,26 @@ class Config:
             num_inference_steps: int = 4,
             width: int = 1024,
             height: int = 1024,
+            guidance: float = 4.0,
     ):
         if width %16 != 0 or height % 16 != 0:
             log.warning("Width and height should be multiples of 16. Rounding down.")
         self.width = 16 * (height // 16)
         self.height = 16 * (width // 16)
-        base_sigmas = Config.base_sigmas(num_inference_steps)
+        self.sigmas = Config.base_sigmas(num_inference_steps)
         self.num_inference_steps = num_inference_steps
-        self.time_steps = base_sigmas * self.num_train_steps
-        self.sigmas = mx.concatenate([base_sigmas, mx.zeros(1)])
+        self.guidance = guidance
 
     @staticmethod
     def base_sigmas(num_inference_steps):
-        sigmas = np.linspace(1.0, 1 / num_inference_steps, num_inference_steps)
+        sigmas = np.linspace(1.0, 0, num_inference_steps+1)
         sigmas = mx.array(sigmas).astype(mx.float32)
         return sigmas
+    
+    def shift_sigmas(self):
+        y1 = 0.5
+        x1 = 256
+        m = (1.15 - y1) / (4096 - x1)
+        b = y1 - m * x1
+        mu = m + b
+        self.sigmas = mx.exp(mu) / (mx.exp(mu) + (1 / self.sigmas - 1))

src/flux_1_schnell/flux.py

@@ -19,8 +19,9 @@ from flux_1_schnell.weights.weight_handler import WeightHandler
 class Flux1:
 
     def __init__(self, repo_id: str):
-        is_dev = "FLUX.1-dev" in repo_id
-        max_t5_length = 512 if is_dev else 256
+        self.is_dev = "FLUX.1-dev" in repo_id
+        # max_t5_length = 512 if self.is_dev else 256
+        max_t5_length = 256
         tokenizers = TokenizerHandler.load_from_disk_or_huggingface(repo_id, max_t5_length)
         self.t5_tokenizer = TokenizerT5(tokenizers.t5, max_length=max_t5_length)
         self.clip_tokenizer = TokenizerCLIP(tokenizers.clip)
@@ -32,6 +33,8 @@ class Flux1:
         self.clip_text_encoder = CLIPEncoder(weights.clip_encoder)
 
     def generate_image(self, seed: int, prompt: str, config: Config = Config()) -> PIL.Image.Image:
+        if self.is_dev:
+            config.shift_sigmas()
         latents = LatentCreator.create(config.height, config.width, seed)
 
         t5_tokens = self.t5_tokenizer.tokenize(prompt)

src/flux_1_schnell/models/transformer/time_text_embed.py

@@ -15,15 +15,14 @@ class TimeTextEmbed(nn.Module):
         self.text_embedder = TextEmbedder()
         self.with_guidance_embed = with_guidance_embed
         if self.with_guidance_embed:
-            self.guidance = mx.broadcast_to(4.0, (1,))
             self.guidance_embedder = GuidanceEmbedder()
         self.timestep_embedder = TimestepEmbedder()
 
-    def forward(self, time_step: mx.array, pooled_projection: mx.array) -> mx.array:
+    def forward(self, time_step: mx.array, pooled_projection: mx.array, guidance: mx.array) -> mx.array:
         time_steps_proj = self._time_proj(time_step)
         time_steps_emb = self.timestep_embedder.forward(time_steps_proj)
         if self.with_guidance_embed:
-            time_steps_emb += self.guidance_embedder.forward(self._time_proj(self.guidance))
+            time_steps_emb += self.guidance_embedder.forward(self._time_proj(guidance))
         pooled_projections = self.text_embedder.forward(pooled_projection)
         conditioning = time_steps_emb + pooled_projections
         return conditioning.astype(Config.precision)

src/flux_1_schnell/models/transformer/transformer.py

@@ -34,10 +34,11 @@ class Transformer(nn.Module):
             hidden_states: mx.array,
             config: Config
     ) -> mx.array:
-        time_step = config.time_steps[t]
+        time_step = config.sigmas[t] * config.num_train_steps
         time_step = mx.broadcast_to(time_step, (1,))
         hidden_states = self.x_embedder(hidden_states)
-        text_embeddings = self.time_text_embed.forward(time_step, pooled_prompt_embeds)
+        guidance = mx.broadcast_to(config.guidance, (1,))
+        text_embeddings = self.time_text_embed.forward(time_step, pooled_prompt_embeds, guidance)
         encoder_hidden_states = self.context_embedder(prompt_embeds)
         txt_ids = Transformer._prepare_text_ids(seq_len = prompt_embeds.shape[1])
         img_ids = Transformer._prepare_latent_image_ids(config.width, config.height)