[Bugfix] Remove NVFP4 scales assertions to fix load_format=dummy (#18861)

Signed-off-by: mgoin <mgoin64@gmail.com>

vllm/model_executor/layers/quantization/modelopt.py

@@ -585,9 +585,11 @@ class ModelOptNvFp4FusedMoE(FusedMoEMethodBase):
     def process_weights_after_loading(self, layer: torch.nn.Module) -> None:
 
         # GEMM 1
-        assert torch.allclose(
-            layer.w13_weight_scale_2[:, 0], layer.w13_weight_scale_2[:, 1]), (
-                "w1_weight_scale_2 must match w3_weight_scale_2")
+        if not torch.allclose(layer.w13_weight_scale_2[:, 0],
+                              layer.w13_weight_scale_2[:, 1]):
+            logger.warning_once(
+                "w1_weight_scale_2 must match w3_weight_scale_2. "
+                "Accuracy may be affected.")
 
         w13_weight_scale_2 = layer.w13_weight_scale_2[:, 0]
         layer.w13_weight_scale_2 = Parameter(w13_weight_scale_2,

vllm/model_executor/layers/quantization/utils/marlin_utils_fp4.py

@@ -22,7 +22,12 @@ def is_fp4_marlin_supported():
 
 
 def fp4_marlin_process_scales(marlin_scales):
-    assert (marlin_scales >= 0).all()
+    if not (marlin_scales >= 0).all():
+        logger.warning_once(
+            "NVFP4 Marlin assumes the scales to be >=0, but has encountered "
+            "negative scales. Accuracy will likely be degraded. This is "
+            "because it changes the scales from FP8-S1E4M3 to a special "
+            "FP8-S0E5M3 format to speedup the dequantization.")
 
     # convert to half first, we would convert to fp8 later
     marlin_scales = marlin_scales.to(torch.half)