Added an always_underloaded underload detection algorithm

neat/locals/underload/trivial.py

@@ -22,6 +22,25 @@ import logging
 log = logging.getLogger(__name__)
 
 
+@contract
+def always_underloaded_factory(time_step, migration_time, params):
+    """ Creates an algorithm that always considers the host underloaded.
+
+    :param time_step: The length of the simulation time step in seconds.
+     :type time_step: int,>=0
+
+    :param migration_time: The VM migration time in time seconds.
+     :type migration_time: float,>=0
+
+    :param params: A dictionary containing the algorithm's parameters.
+     :type params: dict(str: *)
+
+    :return: A function implementing the algorithm.
+     :rtype: function
+    """
+    return lambda utilization, state=None: (True, {})
+
+
 @contract
 def threshold_factory(time_step, migration_time, params):
     """ Creates the threshold underload detection algorithm.

tests/locals/underload/test_trivial.py

@@ -23,6 +23,15 @@ logging.disable(logging.CRITICAL)
 
 class Trivial(TestCase):
 
+    @qc(10)
+    def always_underloaded_factory(
+        time_step=int_(min=0, max=10),
+        migration_time=float_(min=0, max=10),
+        utilization=list_(of=float)
+    ):
+        alg = trivial.always_underloaded_factory(time_step, migration_time, {})
+        assert alg(utilization) == (True, {})
+
     def test_threshold_factory(self):
         alg = trivial.threshold_factory(300, 20., {'threshold': 0.5})
         self.assertEqual(alg([]), (False, {}))
@@ -32,7 +41,6 @@ class Trivial(TestCase):
         self.assertEqual(alg([0.0, 0.6]), (False, {}))
         self.assertEqual(alg([0.0, 1.0]), (False, {}))
 
-
     def test_last_n_average_threshold_factory(self):
         alg = trivial.last_n_average_threshold_factory(
             300, 20., {'threshold': 0.5,
@@ -47,7 +55,7 @@ class Trivial(TestCase):
         self.assertEqual(alg([0.0, 0.2, 1.0]), (False, {}))
         self.assertEqual(alg([0.0, 1.0, 1.0]), (False, {}))
         self.assertEqual(alg([0.0, 0.6, 0.6]), (False, {}))
-        
+
         alg = trivial.last_n_average_threshold_factory(
             300, 20., {'threshold': 0.5,
                        'n': 3})