eq(): better performance by avoiding array comparison when shapes do not match

pyqtgraph/functions.py

@@ -418,6 +418,20 @@ def eq(a, b):
     if a is b:
         return True
 
+    # Avoid comparing large arrays against scalars; this is expensive and we know it should return False.
+    aIsArr = isinstance(a, (np.ndarray, MetaArray))
+    bIsArr = isinstance(b, (np.ndarray, MetaArray))
+    if (aIsArr or bIsArr) and type(a) != type(b):
+        return False
+
+    # If both inputs are arrays, we can speeed up comparison if shapes / dtypes don't match
+    # NOTE: arrays of dissimilar type should be considered unequal even if they are numerically
+    # equal because they may behave differently when computed on.
+    if aIsArr and bIsArr and (a.shape != b.shape or a.dtype != b.dtype):
+        return False
+
+    # Test for equivalence. 
+    # If the test raises a recognized exception, then return Falase
     try:
         try:
             # Sometimes running catch_warnings(module=np) generates AttributeError ???