[Kinetics] Fix handling of integral, explicit reaction orders

If any of the reaction orders differ from the corresponding stoichiometric
coefficients, the reaction needs to be handled as the general case, instead of
just when the orders are non-integral.

include/cantera/kinetics/StoichManager.h

@@ -771,7 +771,7 @@ public:
         }
         bool frac = false;
         for (size_t n = 0; n < stoich.size(); n++) {
-            if (fmod(stoich[n], 1.0) || fmod(order[n], 1.0)) {
+            if (fmod(stoich[n], 1.0) || stoich[n] != order[n]) {
                 frac = true;
                 break;
             }

interfaces/cython/cantera/test/test_kinetics.py

@@ -426,8 +426,8 @@ class ExplicitForwardOrderTest(utilities.CanteraTest):
     def test_irreversibility(self):
         # Reactions are irreversible
         Rr = self.gas.reverse_rate_constants
-        self.assertEqual(Rr[0], 0.0)
+        for i in range(3):
-        self.assertEqual(Rr[1], 0.0)
+            self.assertEqual(Rr[i], 0.0)
 
     def test_rateConstants(self):
         # species order: [H, AR, R1A, R1B, P1]
@@ -436,6 +436,7 @@ class ExplicitForwardOrderTest(utilities.CanteraTest):
         kf = self.gas.forward_rate_constants
         self.assertNear(Rf[0], kf[0] * C[2]**1.5 * C[3]**0.5)
         self.assertNear(Rf[1], kf[1] * C[0]**1.0 * C[4]**0.2)
+        self.assertNear(Rf[2], kf[2] * C[2]**3.0)
 
     def test_ratio1(self):
         rop1 = self.gas.forward_rates_of_progress
@@ -445,6 +446,7 @@ class ExplicitForwardOrderTest(utilities.CanteraTest):
         ratio = rop2/rop1
         self.assertNear(ratio[0], 2**1.5) # order of R1A is 1.5
         self.assertNear(ratio[1], 2**1.0) # order of H is 1.0
+        self.assertNear(ratio[2], 2**3) # order of R1A is 3
 
     def test_ratio2(self):
         rop1 = self.gas.forward_rates_of_progress
@@ -454,6 +456,7 @@ class ExplicitForwardOrderTest(utilities.CanteraTest):
         ratio = rop2/rop1
         self.assertNear(ratio[0], 2**0.5) # order of R1B is 0.5
         self.assertNear(ratio[1], 2**0.2) # order of P1 is 1.0
+        self.assertNear(ratio[2], 2**0.0) # order of R1B is 0
 
 
 class TestSofcKinetics(utilities.CanteraTest):

test/data/explicit-forward-order.inp

@@ -13,8 +13,14 @@ REACTIONS
 R1A+R1B=>H+P1              1e12  0.0   20000.0
   FORD / R1A 1.5 /
   FORD / R1B 0.5 /
+  DUPLICATE
 
 H+P1=>R1A+R1B             5e13 -2.0 5000.0
   FORD / P1 0.2 /
 
+R1A+R1B=>H+P1              1e12  0.0   20000.0
+  FORD / R1A 3.0 /
+  FORD / R1B 0.0 /
+  DUPLICATE
+
 END

test/data/explicit-forward-order.xml

@@ -108,7 +108,7 @@
   <reactionData id="reaction_data">
 
     <!-- reaction 0001    -->
-    <reaction reversible="no" id="0001">
+    <reaction duplicate="yes" reversible="no" id="0001">
       <equation>R1A + R1B =] H + P1</equation>
       <order species="R1B">0.5</order>
       <order species="R1A">1.5</order>
@@ -138,5 +138,21 @@
       <reactants>H:1.0 P1:1</reactants>
       <products>R1B:1 R1A:1.0</products>
     </reaction>
+
+    <!-- reaction 0003    -->
+    <reaction duplicate="yes" reversible="no" id="0003">
+      <equation>R1A + R1B =] H + P1</equation>
+      <order species="R1B">0.0</order>
+      <order species="R1A">3.0</order>
+      <rateCoeff>
+        <Arrhenius>
+           <A>1.000000E+06</A>
+           <b>0.0</b>
+           <E units="cal/mol">20000.000000</E>
+        </Arrhenius>
+      </rateCoeff>
+      <reactants>R1B:1 R1A:1.0</reactants>
+      <products>H:1.0 P1:1</products>
+    </reaction>
   </reactionData>
 </ctml>