[Bugfix] Fix marlin nvfp4 rescaling (#37502)

Signed-off-by: Jinzhen Lin <jinzhen.ljz@antgroup.com>

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

@@ -43,9 +43,9 @@ def _nvfp4_compute_scale_factor(
     ws_float = marlin_scales.float() * (2**7)
     nonzero_mask = ws_float > 0
     if nonzero_mask.any():
-        min_val = ws_float[nonzero_mask].min()
-        if min_val < 2:
-            sf = (2 / min_val).log2().ceil().exp2()
+        max_val = ws_float[nonzero_mask].max()
+        if max_val < 448 * (2**7):
+            sf = (448 * (2**7) / max_val).log2().floor().exp2()
             return sf.item()
     return 1.0
 
@@ -105,7 +105,9 @@ def nvfp4_marlin_process_scales(
     if scale_factor > 1.0:
         marlin_scales = (marlin_scales.float() * scale_factor).to(torch.half)
 
-    marlin_scales = (marlin_scales * (2**7)).view(torch.int16) << 1
+    marlin_scales = marlin_scales * (2**7)
+    marlin_scales[marlin_scales < 2] = 0
+    marlin_scales = marlin_scales.view(torch.int16) << 1
     marlin_scales = marlin_scales.view(torch.float8_e4m3fn)
     marlin_scales = marlin_scales[:, 1::2].contiguous()