Merge pull request #2857 from jsiirola/fix-pow-0

Resolve handling of {}**0 in LinearRepn/QuadraticRepn

Author: mrmundt

pyomo/repn/linear.py

@@ -344,6 +344,8 @@ def _handle_pow_ANY_constant(visitor, node, arg1, arg2):
                 visitor, None, ans, (_type, _arg.duplicate())
             )
         return ans
+    elif exp == 0:
+        return _CONSTANT, 1
     else:
         return _handle_pow_nonlinear(visitor, node, arg1, arg2)
 

pyomo/repn/tests/test_linear.py

@@ -852,6 +852,18 @@ def test_pow_expr(self):
         self.assertEqual(repn.linear, {id(m.x): 1})
         self.assertEqual(repn.nonlinear, None)
 
+        m.p = 0
+
+        cfg = VisitorConfig()
+        repn = LinearRepnVisitor(*cfg).walk_expression(e)
+        self.assertEqual(cfg.subexpr, {})
+        self.assertEqual(cfg.var_map, {id(m.x): m.x})
+        self.assertEqual(cfg.var_order, {id(m.x): 0})
+        self.assertEqual(repn.multiplier, 1)
+        self.assertEqual(repn.constant, 1)
+        self.assertEqual(repn.linear, {})
+        self.assertEqual(repn.nonlinear, None)
+
         m.p = 2
 
         cfg = VisitorConfig()