CLN: fix naming on ddp conversion routines

quantecon/markov/ddp.py

@@ -456,43 +456,43 @@ def _check_action_feasibility(self):
                     'violated for state {s}'.format(s=s)
                 )
 
-    def to_sa_formulation(self, sparse=True):
+    def to_sa_pair_form(self, sparse=True):
         """
         Convert this instance of `DiscreteDP` to SA-pair form
 
         Parameters
         ----------
         sparse : bool, optional(default=True)
-            Should the `Q` matrix be stored as a sparse matrix.
+            Should the `Q` matrix be stored as a sparse matrix?
             If true the CSR format is used
 
         Returns
         -------
         ddp_sa : DiscreteDP
-            The correspnoding DiscreteDP instance in SA form
+            The correspnoding DiscreteDP instance in SA-pair form
 
         Notes
         -----
-        If this instance is already in SA form then it is returned
+        If this instance is already in SA-pair form then it is returned
         un-modified
         """
 
         if self._sa_pair:
             return self
         else:
-            s_ind, a_ind = np.where(np.isfinite(self.R))
+            s_ind, a_ind = np.where(self.R > - np.inf)
             RL = self.R[s_ind, a_ind]
             if sparse:
                 QL = sp.csr_matrix(self.Q[s_ind, a_ind])
             else:
                 QL = self.Q[s_ind, a_ind]
             return DiscreteDP(RL, QL, self.beta, s_ind, a_ind)
 
-    def to_full_formulation(self):
+    def to_product_form(self):
         """
-        Convert this instance of `DiscreteDP` to the "full" form.
+        Convert this instance of `DiscreteDP` to the "product" form.
 
-        The full form uses the version of the init method taking
+        The product form uses the version of the init method taking
         `R`, `Q` and `beta`.
 
         Parameters
@@ -501,18 +501,18 @@ def to_full_formulation(self):
         Returns
         -------
         ddp_sa : DiscreteDP
-            The correspnoding DiscreteDP instance in full form
+            The correspnoding DiscreteDP instance in product form
 
         Notes
         -----
-        If this instance is already in full form then it is returned
+        If this instance is already in product form then it is returned
         un-modified
 
         """
         if self._sa_pair:
             ns = self.num_states
             na = self.a_indices.max() + 1
-            R = np.zeros((ns, na))
+            R = np.full((ns, na), -np.inf)
             R[self.s_indices, self.a_indices] = self.R
             Q = np.zeros((ns, na, ns))
             if self._sparse:

quantecon/markov/tests/test_ddp.py

@@ -126,7 +126,7 @@ def test_ddp_beta_0():
     v_init = [0, 0, 0]
 
     ddp0 = DiscreteDP(R, Q, beta)
-    ddp1 = ddp0.to_sa_formulation()
+    ddp1 = ddp0.to_sa_pair_form()
     methods = ['vi', 'pi', 'mpi']
 
     for ddp in [ddp0, ddp1]:
@@ -252,8 +252,8 @@ def test_ddp_beta_1_not_implemented_error():
     beta = 1
 
     ddp0 = DiscreteDP(R, Q, beta)
-    ddp1 = ddp0.to_sa_formulation()
-    ddp2 = ddp0.to_sa_formulation(sparse=False)
+    ddp1 = ddp0.to_sa_pair_form()
+    ddp2 = ddp0.to_sa_pair_form(sparse=False)
 
     solution_methods = \
         ['value_iteration', 'policy_iteration', 'modified_policy_iteration']
@@ -264,7 +264,7 @@ def test_ddp_beta_1_not_implemented_error():
             assert_raises(NotImplementedError, getattr(ddp, method))
 
 
-def test_ddp_to_sa_and_to_full():
+def test_ddp_to_sa_and_to_product():
     n, m = 3, 2
     R = np.array([[0, 1], [1, 0], [0, 1]])
     Q = np.empty((n, m, n))
@@ -275,12 +275,12 @@ def test_ddp_to_sa_and_to_full():
     sparse_Q = sparse.coo_matrix(np.full((6, 3), 1/3))
 
     ddp = DiscreteDP(R, Q, beta)
-    ddp_sa = ddp.to_sa_formulation()
-    ddp_sa2 = ddp_sa.to_sa_formulation()
-    ddp_sa3 = ddp.to_sa_formulation(sparse=False)
-    ddp2 = ddp_sa.to_full_formulation()
-    ddp3 = ddp_sa2.to_full_formulation()
-    ddp4 = ddp.to_full_formulation()
+    ddp_sa = ddp.to_sa_pair_form()
+    ddp_sa2 = ddp_sa.to_sa_pair_form()
+    ddp_sa3 = ddp.to_sa_pair_form(sparse=False)
+    ddp2 = ddp_sa.to_product_form()
+    ddp3 = ddp_sa2.to_product_form()
+    ddp4 = ddp.to_product_form()
 
     # make sure conversion worked
     for ddp_s in [ddp_sa, ddp_sa2, ddp_sa3]: