Enhance diff and tensor-info logging in dumper grafter (#24512)

test/registered/debug_utils/test_dumper.py

@@ -17,6 +17,7 @@ import torch.distributed as dist
 from sglang.srt.debug_utils.dumper import (
     DumperConfig,
     _collective_with_timeout,
+    _compare_tensors_quick,
     _deepcopy_or_clone,
     _detect_recompute_status,
     _Dumper,
@@ -397,6 +398,37 @@ class TestLog:
         assert ", t=" in out, out
 
 
+class TestCompareTensorsQuick:
+    def test_identical(self):
+        a = torch.tensor([1.0, 2.0, 3.0])
+        s = _compare_tensors_quick(a, a.clone())
+        assert "rel_diff=0" in s, s
+        assert "max_abs=0" in s, s
+
+    def test_diverged(self):
+        a = torch.tensor([1.0, 2.0, 3.0])
+        b = torch.tensor([1.0, 2.0, 4.0])  # last element differs by 1
+        s = _compare_tensors_quick(a, b)
+        assert "max_abs=1" in s, s
+        assert "rel_diff=" in s, s
+
+    def test_shape_mismatch(self):
+        s = _compare_tensors_quick(torch.zeros(3), torch.zeros(4))
+        assert "shape mismatch" in s, s
+
+    def test_dtype_unified(self):
+        s = _compare_tensors_quick(
+            torch.zeros(3, dtype=torch.float32),
+            torch.zeros(3, dtype=torch.float64),
+        )
+        assert "rel_diff=" in s, s
+        assert "max_abs=" in s, s
+
+    def test_empty(self):
+        s = _compare_tensors_quick(torch.zeros(0), torch.zeros(0))
+        assert s == "empty"
+
+
 class TestCollectiveTimeout:
     def test_watchdog_fires_on_timeout(self):
         block_event = threading.Event()