Merge pull request #478 from Axelrod-Python/475

Add line to suppress runtime warning from numpy

Author: marcharper

axelrod/eigen.py

@@ -10,14 +10,18 @@
 
 def normalise(nvec):
     """Normalises the given numpy array."""
-    return nvec / numpy.sqrt(numpy.dot(nvec, nvec))
+    with numpy.errstate(invalid='ignore'):
+        result = nvec / numpy.sqrt(numpy.dot(nvec, nvec))
+    return result
+
 
 def squared_error(vector_1, vector_2):
     """Computes the squared error between two numpy arrays."""
     diff = vector_1 - vector_2
     s = numpy.dot(diff, diff)
     return numpy.sqrt(s)
 
+
 def power_iteration(mat, initial):
     """
     Generator of successive approximations.
@@ -39,6 +43,7 @@ def power_iteration(mat, initial):
         vec = normalise(numpy.dot(mat, vec))
         yield vec
 
+
 def principal_eigenvector(mat, maximum_iterations=None, max_error=1e-8):
     """
     Computes the (normalised) principal eigenvector of the given matrix.