add checkSquareStochastic function to sql mdp

mdpsql.py

@@ -9,6 +9,7 @@ from numpy import arange
 from numpy.random import permutation, random, randint
 
 def exampleRand(S, A):
+    """WARNING: This will delete a database with the same name as 'db'."""
     db = "MDP-%sx%s.db" % (S, A)
     if os.path.exists(db):
         os.remove(db)
@@ -20,14 +21,14 @@ def exampleRand(S, A):
             INSERT INTO info VALUES('states', %s);
             INSERT INTO info VALUES('actions', %s);''' % (S, A)
         c.executescript(cmd)
-        for a in range(A):
+        for a in range(1, A+1):
             cmd = '''
                 CREATE TABLE transition%s (row INTEGER, col INTEGER, prob REAL);
                 CREATE TABLE reward%s (state INTEGER PRIMARY KEY ASC, val REAL);''' % (a, a)
             c.executescript(cmd)
             cmd = "INSERT INTO reward%s(val) VALUES(?)" % a
             c.executemany(cmd, zip(random(S).tolist()))
-            for s in xrange(S):
+            for s in xrange(1, S+1):
                 # to be usefully represented as a sparse matrix, the number of
                 # nonzero entries should be less than 1/3 of dimesion of the
                 # matrix, so S/3
@@ -36,7 +37,7 @@ def exampleRand(S, A):
                 # ==> 10000 loops, best of 3: 141 us per loop
                 # timeit (90894*np.ones(20330, dtype=int)).tolist()
                 # ==> 1000 loops, best of 3: 548 us per loop
-                col = (permutation(arange(S))[0:n]).tolist()
+                col = (permutation(arange(1,S+1))[0:n]).tolist()
                 val = random(n)
                 val = (val / val.sum()).tolist()
                 cmd = "INSERT INTO transition%s VALUES(?, ?, ?)" % a
@@ -68,14 +69,45 @@ class MDP(object):
         except TypeError:
             raise ValueError("Cannot determine number of actions from database. "
                              "There is no name 'actions' in table 'info'.")
+        self._checkSquareStochastic()
         self._initQ()
         self._initResults(initial_V)
     
+    def _checkSquareStochastic(self):
+        # check that the columns of the transition matrices sum to one
+        for a in range(1, self.A + 1):
+            P = "transition%s" % a
+            cmd = "SELECT SUM(s) " \
+                  "  FROM (" \
+                  "       SELECT ABS(SUM(prob)-1)<10e-12 AS s" \
+                  "         FROM "+P+"" \
+                  "        GROUP BY row);"
+            self._cur.execute(cmd)
+            try:
+                if self._cur.fetchone()[0] != self.S:
+                    raise ValueError("The transition matrix for action %s " \
+                                     "is not stochastic." % a)
+            except TypeError:
+                raise StandardError("The check stochastic query for a=%s " \
+                                    "failed." % a)
+            cmd = "SELECT MAX(row) FROM " + P
+            self._cur.execute(cmd)
+            row_max = self._cur.fetchone()[0]
+            if int(row_max) != self.S:
+                raise ValueError("The transition matrix for action %s is " \
+                                 "not square: row_max = %s" % (a, row_max))
+            cmd = "SELECT MAX(col) FROM " + P
+            self._cur.execute(cmd)
+            col_max = self._cur.fetchone()[0]
+            if int(col_max) > row_max:
+                raise ValueError("The transition matrix for action %a id " \
+                                 "not square: col_max = %s" % (a, col_max))
+    
     def _initQ(self):
         self._delQ()
         self._cur.execute("CREATE TABLE Q (state INTEGER, action INTEGER, value REAL);")
-        for a in range(self.A):
-            state = range(self.S)
+        for a in range(1, self.A + 1):
+            state = xrange(1, self.S + 1)
             action = [a] * self.S
             value = [None] * self.S
             cmd = "INSERT INTO Q VALUES(?, ?, ?)"
@@ -198,8 +230,8 @@ class MDP(object):
         return policy, value
     
     def _randomQ(self):
-        for a in range(self.A):
-            state = range(self.S)
+        for a in range(1,self.A+1):
+            state = xrange(1,self.S+1)
             action = [a] * self.S
             value = random(self.S).tolist()
             cmd = "INSERT INTO Q VALUES(?, ?, ?)"
@@ -218,10 +250,10 @@ class ValueIteration(MDP):
         else:
             self.thresh = epsilon
         
-        self._iterate()
+        #self._iterate()
     
     def __del__(self):
-        MDP.__del__()
+        MDP.__del__(self)
     
     def _iterate(self):
         self.time = time()