--fast now takes a number as argument to indicate how fast you want it.

The idea is that you can indicate how much quality vs speed you want.

At the moment:

--fast 2 enables fp16 accumulation if your pytorch supports it.
--fast 5 enables fp8 matrix mult on fp8 models and the optimization above.

--fast without a number enables all optimizations.

comfy/cli_args.py

@@ -130,7 +130,7 @@ class LatentPreviewMethod(enum.Enum):
 
 parser.add_argument("--disable-smart-memory", action="store_true", help="Force ComfyUI to agressively offload to regular ram instead of keeping models in vram when it can.")
 parser.add_argument("--deterministic", action="store_true", help="Make pytorch use slower deterministic algorithms when it can. Note that this might not make images deterministic in all cases.")
-parser.add_argument("--fast", action="store_true", help="Enable some untested and potentially quality deteriorating optimizations.")
+parser.add_argument("--fast", metavar="number", type=int, const=99, default=0, nargs="?", help="Enable some untested and potentially quality deteriorating optimizations. You can pass a number from 0 to 10 for a bigger speed vs quality tradeoff. Using --fast with no number means maximum speed. 2 or larger enables fp16 accumulation, 5 or larger enables fp8 matrix multiplication.")
 
 parser.add_argument("--dont-print-server", action="store_true", help="Don't print server output.")
 parser.add_argument("--quick-test-for-ci", action="store_true", help="Quick test for CI.")

comfy/model_management.py

@@ -280,9 +280,10 @@ def is_amd():
 
 PRIORITIZE_FP16 = False  # TODO: remove and replace with something that shows exactly which dtype is faster than the other
 try:
-    if is_nvidia() and args.fast:
+    if is_nvidia() and args.fast >= 2:
         torch.backends.cuda.matmul.allow_fp16_accumulation = True
         PRIORITIZE_FP16 = True  # TODO: limit to cards where it actually boosts performance
+        logging.info("Enabled fp16 accumulation.")
 except:
     pass
 

comfy/ops.py

@@ -360,7 +360,7 @@ def pick_operations(weight_dtype, compute_dtype, load_device=None, disable_fast_
     if scaled_fp8 is not None:
         return scaled_fp8_ops(fp8_matrix_mult=fp8_compute, scale_input=True, override_dtype=scaled_fp8)
 
-    if fp8_compute and (fp8_optimizations or args.fast) and not disable_fast_fp8:
+    if fp8_compute and (fp8_optimizations or args.fast >= 5) and not disable_fast_fp8:
         return fp8_ops
 
     if compute_dtype is None or weight_dtype == compute_dtype: