ci: make performance regression script more robust with shebang and error guards

Author: poyrazK

scripts/check_perf_regression.py

@@ -1,25 +1,32 @@
+#!/usr/bin/env python3
 import json
 import sys
 import os
 
 def check_regression(current_file, baseline_file, threshold=0.2):
-    if not os.path.exists(baseline_file):
-        print(f"No baseline found at {baseline_file}. Skipping comparison.")
-        return True
-
+    # Load current results - failure here is a fatal error
     try:
         with open(current_file) as f:
             current = json.load(f)
+    except Exception as e:
+        print(f"Error loading current performance results from {current_file}: {e}")
+        return False
+
+    # Load baseline results - missing file is handled gracefully
+    try:
         with open(baseline_file) as f:
             baseline = json.load(f)
-    except Exception as e:
-        print(f"Error loading JSON: {e}")
+    except FileNotFoundError:
+        print(f"No baseline found at {baseline_file}. Skipping comparison.")
         return True
+    except Exception as e:
+        print(f"Error loading baseline performance results from {baseline_file}: {e}")
+        return False
 
     regressions = []
 
     # Create map of baseline metrics
-    base_map = {b['name']: b['real_time'] for b in baseline['benchmarks']}
+    base_map = {b['name']: b.get('real_time') for b in baseline['benchmarks']}
 
     print(f"{'Benchmark':<40} | {'Old (ns)':<12} | {'New (ns)':<12} | {'Change':<10}")
     print("-" * 85)
@@ -28,8 +35,17 @@ def check_regression(current_file, baseline_file, threshold=0.2):
         name = b['name']
         if name in base_map:
             old_time = base_map[name]
-            new_time = b['real_time']
+            new_time = b.get('real_time')
 
+            if old_time is None or new_time is None:
+                print(f"{name:<40} | {'N/A':<12} | {'N/A':<12} | {'N/A':>9}")
+                continue
+
+            # Guard against division by zero
+            if old_time <= 0:
+                print(f"{name:<40} | {old_time:<12.2f} | {new_time:<12.2f} | {'NEW/ZERO':>9}")
+                continue
+
             # Increase in time means decrease in performance
             change = (new_time - old_time) / old_time
             print(f"{name:<40} | {old_time:<12.2f} | {new_time:<12.2f} | {change:>+9.1%}")