Merge 425ed43cc6 into ed7c2c6579

Mark the weight_dtype parameter in UNETLoader (Load Diffusion Model) as
an advanced input to reduce UI complexity for new users. The parameter
is now hidden behind an expandable Advanced section, matching the
pattern used for other advanced inputs like device, tile_size, and
overlap.

Amp-Thread-ID: https://ampcode.com/threads/T-019cbaf1-d3c0-718e-a325-318baba86dec

app/user_manager.py

@@ -6,6 +6,7 @@ import uuid
 import glob
 import shutil
 import logging
+import tempfile
 from aiohttp import web
 from urllib import parse
 from comfy.cli_args import args
@@ -377,8 +378,15 @@ class UserManager():
             try:
                 body = await request.read()
 
-                with open(path, "wb") as f:
-                    f.write(body)
+                dir_name = os.path.dirname(path)
+                fd, tmp_path = tempfile.mkstemp(dir=dir_name)
+                try:
+                    with os.fdopen(fd, "wb") as f:
+                        f.write(body)
+                    os.replace(tmp_path, path)
+                except:
+                    os.unlink(tmp_path)
+                    raise
             except OSError as e:
                 logging.warning(f"Error saving file '{path}': {e}")
                 return web.Response(

comfy/cli_args.py

@@ -149,6 +149,7 @@ parser.add_argument("--reserve-vram", type=float, default=None, help="Set the am
 parser.add_argument("--async-offload", nargs='?', const=2, type=int, default=None, metavar="NUM_STREAMS", help="Use async weight offloading. An optional argument controls the amount of offload streams. Default is 2. Enabled by default on Nvidia.")
 parser.add_argument("--disable-async-offload", action="store_true", help="Disable async weight offloading.")
 parser.add_argument("--disable-dynamic-vram", action="store_true", help="Disable dynamic VRAM and use estimate based model loading.")
+parser.add_argument("--enable-dynamic-vram", action="store_true", help="Enable dynamic VRAM on systems where it's not enabled by default.")
 
 parser.add_argument("--force-non-blocking", action="store_true", help="Force ComfyUI to use non-blocking operations for all applicable tensors. This may improve performance on some non-Nvidia systems but can cause issues with some workflows.")
 
@@ -262,4 +263,6 @@ else:
     args.fast = set(args.fast)
 
 def enables_dynamic_vram():
+    if args.enable_dynamic_vram:
+        return True
     return not args.disable_dynamic_vram and not args.highvram and not args.gpu_only and not args.novram and not args.cpu

comfy/ldm/hunyuan3dv2_1/hunyuandit.py

@@ -343,6 +343,7 @@ class CrossAttention(nn.Module):
             k.reshape(b, s2, self.num_heads * self.head_dim),
             v,
             heads=self.num_heads,
+            low_precision_attention=False,
         )
 
         out = self.out_proj(x)
@@ -412,6 +413,7 @@ class Attention(nn.Module):
             key.reshape(B, N, self.num_heads * self.head_dim),
             value,
             heads=self.num_heads,
+            low_precision_attention=False,
         )
 
         x = self.out_proj(x)

comfy/ops.py

@@ -776,6 +776,71 @@ from .quant_ops import (
 )
 
 
+class QuantLinearFunc(torch.autograd.Function):
+    """Custom autograd function for quantized linear: quantized forward, compute_dtype backward.
+    Handles any input rank by flattening to 2D for matmul and restoring shape after.
+    """
+
+    @staticmethod
+    def forward(ctx, input_float, weight, bias, layout_type, input_scale, compute_dtype):
+        input_shape = input_float.shape
+        inp = input_float.detach().flatten(0, -2)  # zero-cost view to 2D
+
+        # Quantize input (same as inference path)
+        if layout_type is not None:
+            q_input = QuantizedTensor.from_float(inp, layout_type, scale=input_scale)
+        else:
+            q_input = inp
+
+        w = weight.detach() if weight.requires_grad else weight
+        b = bias.detach() if bias is not None and bias.requires_grad else bias
+
+        output = torch.nn.functional.linear(q_input, w, b)
+
+        # Restore original input shape
+        if len(input_shape) > 2:
+            output = output.unflatten(0, input_shape[:-1])
+
+        ctx.save_for_backward(input_float, weight)
+        ctx.input_shape = input_shape
+        ctx.has_bias = bias is not None
+        ctx.compute_dtype = compute_dtype
+        ctx.weight_requires_grad = weight.requires_grad
+
+        return output
+
+    @staticmethod
+    @torch.autograd.function.once_differentiable
+    def backward(ctx, grad_output):
+        input_float, weight = ctx.saved_tensors
+        compute_dtype = ctx.compute_dtype
+        grad_2d = grad_output.flatten(0, -2).to(compute_dtype)
+
+        # Dequantize weight to compute dtype for backward matmul
+        if isinstance(weight, QuantizedTensor):
+            weight_f = weight.dequantize().to(compute_dtype)
+        else:
+            weight_f = weight.to(compute_dtype)
+
+        # grad_input = grad_output @ weight
+        grad_input = torch.mm(grad_2d, weight_f)
+        if len(ctx.input_shape) > 2:
+            grad_input = grad_input.unflatten(0, ctx.input_shape[:-1])
+
+        # grad_weight (only if weight requires grad, typically frozen for quantized training)
+        grad_weight = None
+        if ctx.weight_requires_grad:
+            input_f = input_float.flatten(0, -2).to(compute_dtype)
+            grad_weight = torch.mm(grad_2d.t(), input_f)
+
+        # grad_bias
+        grad_bias = None
+        if ctx.has_bias:
+            grad_bias = grad_2d.sum(dim=0)
+
+        return grad_input, grad_weight, grad_bias, None, None, None
+
+
 def mixed_precision_ops(quant_config={}, compute_dtype=torch.bfloat16, full_precision_mm=False, disabled=[]):
     class MixedPrecisionOps(manual_cast):
         _quant_config = quant_config
@@ -970,10 +1035,37 @@ def mixed_precision_ops(quant_config={}, compute_dtype=torch.bfloat16, full_prec
                 #If cast needs to apply lora, it should be done in the compute dtype
                 compute_dtype = input.dtype
 
-                if (getattr(self, 'layout_type', None) is not None and
+                _use_quantized = (
+                    getattr(self, 'layout_type', None) is not None and
                     not isinstance(input, QuantizedTensor) and not self._full_precision_mm and
                     not getattr(self, 'comfy_force_cast_weights', False) and
-                    len(self.weight_function) == 0 and len(self.bias_function) == 0):
+                    len(self.weight_function) == 0 and len(self.bias_function) == 0
+                )
+
+                # Training path: quantized forward with compute_dtype backward via autograd function
+                if (input.requires_grad and _use_quantized):
+
+                    weight, bias, offload_stream = cast_bias_weight(
+                        self,
+                        input,
+                        offloadable=True,
+                        compute_dtype=compute_dtype,
+                        want_requant=True
+                    )
+
+                    scale = getattr(self, 'input_scale', None)
+                    if scale is not None:
+                        scale = comfy.model_management.cast_to_device(scale, input.device, None)
+
+                    output = QuantLinearFunc.apply(
+                        input, weight, bias, self.layout_type, scale, compute_dtype
+                    )
+
+                    uncast_bias_weight(self, weight, bias, offload_stream)
+                    return output
+
+                # Inference path (unchanged)
+                if _use_quantized:
 
                     # Reshape 3D tensors to 2D for quantization (needed for NVFP4 and others)
                     input_reshaped = input.reshape(-1, input_shape[2]) if input.ndim == 3 else input
@@ -1021,7 +1113,10 @@ def mixed_precision_ops(quant_config={}, compute_dtype=torch.bfloat16, full_prec
                 for key, param in self._parameters.items():
                     if param is None:
                         continue
-                    self.register_parameter(key, torch.nn.Parameter(fn(param), requires_grad=False))
+                    p = fn(param)
+                    if p.is_inference():
+                        p = p.clone()
+                    self.register_parameter(key, torch.nn.Parameter(p, requires_grad=False))
                 for key, buf in self._buffers.items():
                     if buf is not None:
                         self._buffers[key] = fn(buf)

comfy/utils.py

@@ -897,6 +897,10 @@ def set_attr(obj, attr, value):
     return prev
 
 def set_attr_param(obj, attr, value):
+    # Clone inference tensors (created under torch.inference_mode) since
+    # their version counter is frozen and nn.Parameter() cannot wrap them.
+    if (not torch.is_inference_mode_enabled()) and value.is_inference():
+        value = value.clone()
     return set_attr(obj, attr, torch.nn.Parameter(value, requires_grad=False))
 
 def set_attr_buffer(obj, attr, value):

comfy_extras/nodes_train.py

@@ -15,6 +15,7 @@ import comfy.sampler_helpers
 import comfy.sd
 import comfy.utils
 import comfy.model_management
+from comfy.cli_args import args, PerformanceFeature
 import comfy_extras.nodes_custom_sampler
 import folder_paths
 import node_helpers
@@ -138,6 +139,7 @@ class TrainSampler(comfy.samplers.Sampler):
         training_dtype=torch.bfloat16,
         real_dataset=None,
         bucket_latents=None,
+        use_grad_scaler=False,
     ):
         self.loss_fn = loss_fn
         self.optimizer = optimizer
@@ -152,6 +154,8 @@ class TrainSampler(comfy.samplers.Sampler):
         self.bucket_latents: list[torch.Tensor] | None = (
             bucket_latents  # list of (Bi, C, Hi, Wi)
         )
+        # GradScaler for fp16 training
+        self.grad_scaler = torch.amp.GradScaler() if use_grad_scaler else None
         # Precompute bucket offsets and weights for sampling
         if bucket_latents is not None:
             self._init_bucket_data(bucket_latents)
@@ -204,10 +208,13 @@ class TrainSampler(comfy.samplers.Sampler):
                 batch_sigmas.requires_grad_(True),
                 **batch_extra_args,
             )
-            loss = self.loss_fn(x0_pred, x0)
+            loss = self.loss_fn(x0_pred.float(), x0.float())
         if bwd:
             bwd_loss = loss / self.grad_acc
-            bwd_loss.backward()
+            if self.grad_scaler is not None:
+                self.grad_scaler.scale(bwd_loss).backward()
+            else:
+                bwd_loss.backward()
         return loss
 
     def _generate_batch_sigmas(self, model_wrap, batch_size, device):
@@ -307,7 +314,10 @@ class TrainSampler(comfy.samplers.Sampler):
             )
             total_loss += loss
         total_loss = total_loss / self.grad_acc / len(indicies)
-        total_loss.backward()
+        if self.grad_scaler is not None:
+            self.grad_scaler.scale(total_loss).backward()
+        else:
+            total_loss.backward()
         if self.loss_callback:
             self.loss_callback(total_loss.item())
         pbar.set_postfix({"loss": f"{total_loss.item():.4f}"})
@@ -348,12 +358,18 @@ class TrainSampler(comfy.samplers.Sampler):
                 self._train_step_multires_mode(model_wrap, cond, extra_args, noisegen, latent_image, dataset_size, pbar)
 
             if (i + 1) % self.grad_acc == 0:
+                if self.grad_scaler is not None:
+                    self.grad_scaler.unscale_(self.optimizer)
                 for param_groups in self.optimizer.param_groups:
                     for param in param_groups["params"]:
                         if param.grad is None:
                             continue
                         param.grad.data = param.grad.data.to(param.data.dtype)
-                self.optimizer.step()
+                if self.grad_scaler is not None:
+                    self.grad_scaler.step(self.optimizer)
+                    self.grad_scaler.update()
+                else:
+                    self.optimizer.step()
                 self.optimizer.zero_grad()
             ui_pbar.update(1)
         torch.cuda.empty_cache()
@@ -1004,9 +1020,9 @@ class TrainLoraNode(io.ComfyNode):
                 ),
                 io.Combo.Input(
                     "training_dtype",
-                    options=["bf16", "fp32"],
+                    options=["bf16", "fp32", "none"],
                     default="bf16",
-                    tooltip="The dtype to use for training.",
+                    tooltip="The dtype to use for training. 'none' preserves the model's native compute dtype instead of overriding it. For fp16 models, GradScaler is automatically enabled.",
                 ),
                 io.Combo.Input(
                     "lora_dtype",
@@ -1035,7 +1051,7 @@ class TrainLoraNode(io.ComfyNode):
                 io.Boolean.Input(
                     "offloading",
                     default=False,
-                    tooltip="Offload the Model to RAM. Requires Bypass Mode.",
+                    tooltip="Offload model weights to CPU during training to save GPU memory.",
                 ),
                 io.Combo.Input(
                     "existing_lora",
@@ -1120,22 +1136,32 @@ class TrainLoraNode(io.ComfyNode):
 
         # Setup model and dtype
         mp = model.clone()
-        dtype = node_helpers.string_to_torch_dtype(training_dtype)
+        use_grad_scaler = False
+        if training_dtype != "none":
+            dtype = node_helpers.string_to_torch_dtype(training_dtype)
+            mp.set_model_compute_dtype(dtype)
+        else:
+            # Detect model's native dtype for autocast
+            model_dtype = mp.model.get_dtype()
+            if model_dtype == torch.float16:
+                dtype = torch.float16
+                use_grad_scaler = True
+                # Warn about fp16 accumulation instability during training
+                if PerformanceFeature.Fp16Accumulation in args.fast:
+                    logging.warning(
+                        "WARNING: FP16 model detected with fp16_accumulation enabled. "
+                        "This combination can be numerically unstable during training and may cause NaN values. "
+                        "Suggested fixes: 1) Set training_dtype to 'bf16', or 2) Disable fp16_accumulation (remove from --fast flags)."
+                    )
+            else:
+                # For fp8, bf16, or other dtypes, use bf16 autocast
+                dtype = torch.bfloat16
         lora_dtype = node_helpers.string_to_torch_dtype(lora_dtype)
-        mp.set_model_compute_dtype(dtype)
-
-        if mp.is_dynamic():
-            if not bypass_mode:
-                logging.info("Training MP is Dynamic - forcing bypass mode. Start comfy with --highvram to force weight diff mode")
-                bypass_mode = True
-            offloading = True
-        elif offloading:
-            if not bypass_mode:
-                logging.info("Training Offload selected - forcing bypass mode. Set bypass = True to remove this message")
 
         # Prepare latents and compute counts
+        latents_dtype = dtype if dtype not in (None,) else torch.bfloat16
         latents, num_images, multi_res = _prepare_latents_and_count(
-            latents, dtype, bucket_mode
+            latents, latents_dtype, bucket_mode
         )
 
         # Validate and expand conditioning
@@ -1201,6 +1227,7 @@ class TrainLoraNode(io.ComfyNode):
                     seed=seed,
                     training_dtype=dtype,
                     bucket_latents=latents,
+                    use_grad_scaler=use_grad_scaler,
                 )
             else:
                 train_sampler = TrainSampler(
@@ -1213,6 +1240,7 @@ class TrainLoraNode(io.ComfyNode):
                     seed=seed,
                     training_dtype=dtype,
                     real_dataset=latents if multi_res else None,
+                    use_grad_scaler=use_grad_scaler,
                 )
 
             # Setup guider
@@ -1337,7 +1365,7 @@ class SaveLoRA(io.ComfyNode):
                 io.Int.Input(
                     "steps",
                     optional=True,
-                    tooltip="Optional: The number of steps to LoRA has been trained for, used to name the saved file.",
+                    tooltip="Optional: The number of steps the LoRA has been trained for, used to name the saved file.",
                 ),
             ],
             outputs=[],

main.py

@@ -206,8 +206,8 @@ import hook_breaker_ac10a0
 import comfy.memory_management
 import comfy.model_patcher
 
-if enables_dynamic_vram() and comfy.model_management.is_nvidia() and not comfy.model_management.is_wsl():
-    if comfy.model_management.torch_version_numeric < (2, 8):
+if args.enable_dynamic_vram or (enables_dynamic_vram() and comfy.model_management.is_nvidia() and not comfy.model_management.is_wsl()):
+    if (not args.enable_dynamic_vram) and (comfy.model_management.torch_version_numeric < (2, 8)):
         logging.warning("Unsupported Pytorch detected. DynamicVRAM support requires Pytorch version 2.8 or later. Falling back to legacy ModelPatcher. VRAM estimates may be unreliable especially on Windows")
     elif comfy_aimdo.control.init_device(comfy.model_management.get_torch_device().index):
         if args.verbose == 'DEBUG':

nodes.py

@@ -952,7 +952,7 @@ class UNETLoader:
     @classmethod
     def INPUT_TYPES(s):
         return {"required": { "unet_name": (folder_paths.get_filename_list("diffusion_models"), ),
-                              "weight_dtype": (["default", "fp8_e4m3fn", "fp8_e4m3fn_fast", "fp8_e5m2"],)
+                              "weight_dtype": (["default", "fp8_e4m3fn", "fp8_e4m3fn_fast", "fp8_e5m2"], {"advanced": True})
                              }}
     RETURN_TYPES = ("MODEL",)
     FUNCTION = "load_unet"

requirements.txt

@@ -1,5 +1,5 @@
 comfyui-frontend-package==1.41.20
-comfyui-workflow-templates==0.9.21
+comfyui-workflow-templates==0.9.26
 comfyui-embedded-docs==0.4.3
 torch
 torchsde