add idempotent note and test

theano/gof/tests/test_utils.py

@@ -10,6 +10,19 @@ def test_give_variables_names():
     assert all(var.name for var in variables)
     assert unique([var.name for var in variables])
 
+def test_give_variables_names_idempotence():
+    x = theano.tensor.matrix('x')
+    y = x + 1
+    z = theano.tensor.dot(x, y)
+    variables = (x, y, z)
+
+    give_variables_names(variables)
+    names = [var.name for var in variables]
+    give_variables_names(variables)
+    names2 = [var.name for var in variables]
+
+    assert names == names2
+
 def test_give_variables_names_small():
     x = theano.tensor.matrix('x')
     y = theano.tensor.dot(x, x)

theano/gof/utils.py

@@ -341,7 +341,9 @@ def hist(coll):
     return counts
 
 def give_variables_names(variables):
-    """ Gives unique names to an iterable of variables. Modifies input."""
+    """ Gives unique names to an iterable of variables. Modifies input.
+
+    This function is idempotent."""
     names = map(lambda var: var.name, variables)
     h = hist(names)
     bad_var = lambda var: not var.name or h[var.name] > 1