Make the stochastic fp8 rounding reproducible.

comfy/float.py

@@ -1,18 +1,18 @@
 import torch
 import math
 
-def calc_mantissa(abs_x, exponent, normal_mask, MANTISSA_BITS, EXPONENT_BIAS):
+def calc_mantissa(abs_x, exponent, normal_mask, MANTISSA_BITS, EXPONENT_BIAS, generator=None):
     mantissa_scaled = torch.where(
         normal_mask,
         (abs_x / (2.0 ** (exponent - EXPONENT_BIAS)) - 1.0) * (2**MANTISSA_BITS),
         (abs_x / (2.0 ** (-EXPONENT_BIAS + 1 - MANTISSA_BITS)))
     )
 
-    mantissa_scaled += torch.rand_like(mantissa_scaled)
+    mantissa_scaled += torch.rand(mantissa_scaled.size(), dtype=mantissa_scaled.dtype, layout=mantissa_scaled.layout, device=mantissa_scaled.device, generator=generator)
     return mantissa_scaled.floor() / (2**MANTISSA_BITS)
 
 #Not 100% sure about this
-def manual_stochastic_round_to_float8(x, dtype):
+def manual_stochastic_round_to_float8(x, dtype, generator=None):
     if dtype == torch.float8_e4m3fn:
         EXPONENT_BITS, MANTISSA_BITS, EXPONENT_BIAS = 4, 3, 7
     elif dtype == torch.float8_e5m2:
@@ -34,7 +34,7 @@ def manual_stochastic_round_to_float8(x, dtype):
     # Combine mantissa calculation and rounding
     normal_mask = ~(exponent == 0)
 
-    abs_x[:] = calc_mantissa(abs_x, exponent, normal_mask, MANTISSA_BITS, EXPONENT_BIAS)
+    abs_x[:] = calc_mantissa(abs_x, exponent, normal_mask, MANTISSA_BITS, EXPONENT_BIAS, generator=generator)
 
     sign *= torch.where(
         normal_mask,
@@ -47,7 +47,7 @@ def manual_stochastic_round_to_float8(x, dtype):
 
 
 
-def stochastic_rounding(value, dtype):
+def stochastic_rounding(value, dtype, seed=0):
     if dtype == torch.float32:
         return value.to(dtype=torch.float32)
     if dtype == torch.float16:
@@ -55,6 +55,8 @@ def stochastic_rounding(value, dtype):
     if dtype == torch.bfloat16:
         return value.to(dtype=torch.bfloat16)
     if dtype == torch.float8_e4m3fn or dtype == torch.float8_e5m2:
-        return manual_stochastic_round_to_float8(value, dtype)
+        generator = torch.Generator(device=value.device)
+        generator.manual_seed(seed)
+        return manual_stochastic_round_to_float8(value, dtype, generator=generator)
 
     return value.to(dtype=dtype)

comfy/model_patcher.py

@@ -30,6 +30,18 @@ import comfy.model_management
 import comfy.lora
 from comfy.types import UnetWrapperFunction
 
+def string_to_seed(data):
+    crc = 0xFFFFFFFF
+    for byte in data:
+        if isinstance(byte, str):
+            byte = ord(byte)
+        crc ^= byte
+        for _ in range(8):
+            if crc & 1:
+                crc = (crc >> 1) ^ 0xEDB88320
+            else:
+                crc >>= 1
+    return crc ^ 0xFFFFFFFF
 
 def set_model_options_patch_replace(model_options, patch, name, block_name, number, transformer_index=None):
     to = model_options["transformer_options"].copy()
@@ -309,7 +321,7 @@ class ModelPatcher:
         else:
             temp_weight = weight.to(torch.float32, copy=True)
         out_weight = comfy.lora.calculate_weight(self.patches[key], temp_weight, key)
-        out_weight = comfy.float.stochastic_rounding(out_weight, weight.dtype)
+        out_weight = comfy.float.stochastic_rounding(out_weight, weight.dtype, seed=string_to_seed(key))
         if inplace_update:
             comfy.utils.copy_to_param(self.model, key, out_weight)
         else: