add experimental split mode for FLUX

library/flux_models.py

@@ -918,3 +918,168 @@ class Flux(nn.Module):
 
         img = self.final_layer(img, vec)  # (N, T, patch_size ** 2 * out_channels)
         return img
+
+
+class FluxUpper(nn.Module):
+    """
+    Transformer model for flow matching on sequences.
+    """
+
+    def __init__(self, params: FluxParams):
+        super().__init__()
+
+        self.params = params
+        self.in_channels = params.in_channels
+        self.out_channels = self.in_channels
+        if params.hidden_size % params.num_heads != 0:
+            raise ValueError(f"Hidden size {params.hidden_size} must be divisible by num_heads {params.num_heads}")
+        pe_dim = params.hidden_size // params.num_heads
+        if sum(params.axes_dim) != pe_dim:
+            raise ValueError(f"Got {params.axes_dim} but expected positional dim {pe_dim}")
+        self.hidden_size = params.hidden_size
+        self.num_heads = params.num_heads
+        self.pe_embedder = EmbedND(dim=pe_dim, theta=params.theta, axes_dim=params.axes_dim)
+        self.img_in = nn.Linear(self.in_channels, self.hidden_size, bias=True)
+        self.time_in = MLPEmbedder(in_dim=256, hidden_dim=self.hidden_size)
+        self.vector_in = MLPEmbedder(params.vec_in_dim, self.hidden_size)
+        self.guidance_in = MLPEmbedder(in_dim=256, hidden_dim=self.hidden_size) if params.guidance_embed else nn.Identity()
+        self.txt_in = nn.Linear(params.context_in_dim, self.hidden_size)
+
+        self.double_blocks = nn.ModuleList(
+            [
+                DoubleStreamBlock(
+                    self.hidden_size,
+                    self.num_heads,
+                    mlp_ratio=params.mlp_ratio,
+                    qkv_bias=params.qkv_bias,
+                )
+                for _ in range(params.depth)
+            ]
+        )
+
+        self.gradient_checkpointing = False
+
+    @property
+    def device(self):
+        return next(self.parameters()).device
+
+    @property
+    def dtype(self):
+        return next(self.parameters()).dtype
+
+    def enable_gradient_checkpointing(self):
+        self.gradient_checkpointing = True
+
+        self.time_in.enable_gradient_checkpointing()
+        self.vector_in.enable_gradient_checkpointing()
+        self.guidance_in.enable_gradient_checkpointing()
+
+        for block in self.double_blocks:
+            block.enable_gradient_checkpointing()
+
+        print("FLUX: Gradient checkpointing enabled.")
+
+    def disable_gradient_checkpointing(self):
+        self.gradient_checkpointing = False
+
+        self.time_in.disable_gradient_checkpointing()
+        self.vector_in.disable_gradient_checkpointing()
+        self.guidance_in.disable_gradient_checkpointing()
+
+        for block in self.double_blocks:
+            block.disable_gradient_checkpointing()
+
+        print("FLUX: Gradient checkpointing disabled.")
+
+    def forward(
+        self,
+        img: Tensor,
+        img_ids: Tensor,
+        txt: Tensor,
+        txt_ids: Tensor,
+        timesteps: Tensor,
+        y: Tensor,
+        guidance: Tensor | None = None,
+    ) -> Tensor:
+        if img.ndim != 3 or txt.ndim != 3:
+            raise ValueError("Input img and txt tensors must have 3 dimensions.")
+
+        # running on sequences img
+        img = self.img_in(img)
+        vec = self.time_in(timestep_embedding(timesteps, 256))
+        if self.params.guidance_embed:
+            if guidance is None:
+                raise ValueError("Didn't get guidance strength for guidance distilled model.")
+            vec = vec + self.guidance_in(timestep_embedding(guidance, 256))
+        vec = vec + self.vector_in(y)
+        txt = self.txt_in(txt)
+
+        ids = torch.cat((txt_ids, img_ids), dim=1)
+        pe = self.pe_embedder(ids)
+
+        for block in self.double_blocks:
+            img, txt = block(img=img, txt=txt, vec=vec, pe=pe)
+
+        return img, txt, vec, pe
+
+
+class FluxLower(nn.Module):
+    """
+    Transformer model for flow matching on sequences.
+    """
+
+    def __init__(self, params: FluxParams):
+        super().__init__()
+        self.hidden_size = params.hidden_size
+        self.num_heads = params.num_heads
+        self.out_channels = params.in_channels
+
+        self.single_blocks = nn.ModuleList(
+            [
+                SingleStreamBlock(self.hidden_size, self.num_heads, mlp_ratio=params.mlp_ratio)
+                for _ in range(params.depth_single_blocks)
+            ]
+        )
+
+        self.final_layer = LastLayer(self.hidden_size, 1, self.out_channels)
+
+        self.gradient_checkpointing = False
+
+    @property
+    def device(self):
+        return next(self.parameters()).device
+
+    @property
+    def dtype(self):
+        return next(self.parameters()).dtype
+
+    def enable_gradient_checkpointing(self):
+        self.gradient_checkpointing = True
+
+        for block in self.single_blocks:
+            block.enable_gradient_checkpointing()
+
+        print("FLUX: Gradient checkpointing enabled.")
+
+    def disable_gradient_checkpointing(self):
+        self.gradient_checkpointing = False
+
+        for block in self.single_blocks:
+            block.disable_gradient_checkpointing()
+
+        print("FLUX: Gradient checkpointing disabled.")
+
+    def forward(
+        self,
+        img: Tensor,
+        txt: Tensor,
+        vec: Tensor | None = None,
+        pe: Tensor | None = None,
+    ) -> Tensor:
+        img = torch.cat((txt, img), 1)
+        for block in self.single_blocks:
+            img = block(img, vec=vec, pe=pe)
+        img = img[:, txt.shape[1] :, ...]
+
+        img = self.final_layer(img, vec)  # (N, T, patch_size ** 2 * out_channels)
+        return img