[Auto Sync] Update test_deterministic.py (20260214) (#18839)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Jiayi Yuan <34369239+jy-yuan@users.noreply.github.com>

python/sglang/test/test_deterministic.py

@@ -346,10 +346,46 @@ class TokenIdsAndLogprobs:
             print(f"✅ Logprobs match:", a.logprobs[:5])
         else:
             print(f"❌ Logprobs mismatch")
-            # Only print last 10 elements for readability
+
-            n_show = 10
+            # Find first divergent position
+            first_div = None
+            for idx, (la, lb) in enumerate(zip(a.logprobs, b.logprobs)):
+                if la != lb:
+                    first_div = idx
+                    break
+
+            n_show = 5
+            if first_div is not None:
+                print(f"    First divergence at position {first_div}/{len(a.logprobs)}")
+                # Show n_show elements starting from the divergent point
+                a_show = a.logprobs[first_div : first_div + n_show]
+                b_show = b.logprobs[first_div : first_div + n_show]
+                diff_show = [
+                    abs(x - y) if x is not None and y is not None else float("nan")
+                    for x, y in zip(a_show, b_show)
+                ]
+                pos_range = f"[{first_div}:{first_div + len(a_show)}]"
+                label_width = len(f"A {pos_range}")
+                print(
+                    f"    A {pos_range}: ",
+                    [f"{x:.10f}" if x is not None else "None" for x in a_show],
+                )
+                print(
+                    f"    B {pos_range}: ",
+                    [f"{x:.10f}" if x is not None else "None" for x in b_show],
+                )
+                print(
+                    f"    {'Diff':<{label_width}}: ",
+                    [f"{x:.10e}" for x in diff_show],
+                )
+            else:
+                # Fallback to tail (shouldn't happen if logprobs_match is False)
                 a_show = a.logprobs[-n_show:]
                 b_show = b.logprobs[-n_show:]
+                diff_show = [
+                    abs(x - y) if x is not None and y is not None else float("nan")
+                    for x, y in zip(a_show, b_show)
+                ]
                 print(
                     "    A:    ...  ",
                     [f"{x:.10f}" if x is not None else "None" for x in a_show],
@@ -360,14 +396,10 @@ class TokenIdsAndLogprobs:
                     [f"{x:.10f}" if x is not None else "None" for x in b_show],
                     f"({len(b.logprobs)} total)" if len(b.logprobs) > n_show else "",
                 )
-            diff = [
-                abs(x - y) if x is not None else float("nan")
-                for x, y in zip(a.logprobs, b.logprobs)
-            ]
                 print(
-                "    Diff:",
+                    "    Diff: ...  ",
-                [f"{x:.10e}" for x in diff[-n_show:]],
+                    [f"{x:.10e}" for x in diff_show],
-                f"... ({len(diff)} total)" if len(diff) > n_show else "",
+                    f"({len(a.logprobs)} total)" if len(a.logprobs) > n_show else "",
                 )
 
             # Compute KL-divergence using K3 approximation