Fix nondeterministic error in measure_x

Looks like nondeterminism in `next(d.iterkeys())` was breaking
consistency with A&B. Next up: switching determinism on or off.

abp/graphstate.py

@@ -144,10 +144,12 @@ class GraphState(object):
 
     def toggle_edges(self, a, b):
         """ Toggle edges between vertex sets a and b """
+        # TODO: i'm pretty sure this is just a single-line it.combinations or equiv
         done = set()
         for i, j in it.product(a, b):
-            if i == j and not (i, j) in done:
-                done.add((i, j), (j, i))
+            if i != j and not (i, j) in done:
+                done.add((i, j))
+                done.add((j, i))
                 self.toggle_edge(i, j)
 
     def measure_x(self, node, result):
@@ -156,9 +158,11 @@ class GraphState(object):
             return 0
 
         # Pick a vertex
-        friend = next(self.adj[node].iterkeys())
+        #friend = next(self.adj[node].iterkeys())
+        # TODO this is enforced determinism for testing purposes
+        friend = sorted(self.adj[node].keys())[0] 
 
-        # TODO: yuk yuk yuk
+        # Update the VOPs. TODO: pretty ugly
         if result:
             # Do a z on all ngb(vb) \ ngb(v) \ {v}, and some other stuff
             self.act_local_rotation(node, "pz")
@@ -171,7 +175,7 @@ class GraphState(object):
             for n in set(self.adj[node]) - set(self.adj[friend]) - {friend}:
                 self.act_local_rotation(n, "pz")
 
-        # TODO: Yuk. Just awful!
+        # Toggle the edges. TODO: Yuk. Just awful!
         a = set(self.adj[node].keys())
         b = set(self.adj[friend].keys())
         self.toggle_edges(a, b)

tests/dummy.py

@@ -1,5 +1,6 @@
 from abp import GraphState, clifford
 from anders_briegel import graphsim
+import numpy as np
 
 def random_state(N=10, messy=True):
     """ A state to test on """

tests/test_measurement_against_anders_and_briegel.py

@@ -4,7 +4,7 @@ import numpy as np
 from tqdm import tqdm
 import dummy
 
-N = 2
+N = 10
 REPEATS = 10
 m = {1: graphsim.lco_X, 2: graphsim.lco_Y, 3: graphsim.lco_Z}
 
@@ -21,13 +21,25 @@ def _test_multiqubit_measurement_pz():
         #assert a.to_json() == b.to_json(), a
 
 
-def test_multiqubit_pz():
-    for measurement in (3, 2,):
+def test_2qubit():
+    """ Relentless testing of measurements """
+    for measurement in (3, 2, 1):
         for outcome in (0, 1):
             a, b = dummy.bell()
             a.measure(0, str(measurement), outcome)
             b.measure(0, m[measurement], None, outcome)
-            print a.to_json()
-            print b.to_json()
+            assert a == b, "FUCK"
+            #print a.to_json()
+            #print b.to_json()
             assert a == b, (measurement, outcome)
                 
+def test_multiqubit():
+    """ Relentless testing of measurements """
+    for measurement in (1,):
+        for i in tqdm(range(1000), "Testing {} measurement".format(measurement)):
+            for outcome in (0, 1):
+                a, b = dummy.random_state(N, messy=False)
+                a.measure(0, str(measurement), outcome)
+                b.measure(0, m[measurement], None, outcome)
+                assert a == b, (measurement, outcome)
+