add computation of a lower bound for the optimal makespan

tests/test_dataDistribution.py

@@ -285,6 +285,33 @@ class TestDataDistribution(unittest.TestCase):
         self.assertEqual(9, max(total_folder_sizes))
         self.assertEqual(36, sum(total_folder_sizes))
 
+    def test_get_lower_bound_on_makespan(self):
+        folder_sizes = [1]
+        num_folders = 5
+        osd_bandwidths = [1]
+        num_osds = 4
+
+        distribution = dataDistribution.DataDistribution()
+        distribution.add_osd_list(create_test_osd_list(num_osds, osd_bandwidths))
+        distribution.add_folders(create_test_folder_list(num_folders, folder_sizes), random_osd_assignment=True)
+
+        self.assertEqual(5 / 4, distribution.get_lower_bound_on_makespan())
+
+        folder_sizes = [1]
+        num_folders = 60
+        osd_bandwidths = [3, 2, 1]
+        osd_capacities = [2, 5, 100]
+        num_osds = 4
+
+        distribution = dataDistribution.DataDistribution()
+        distribution.add_osd_list(create_test_osd_list(num_osds, osd_bandwidths))
+        distribution.set_osd_bandwidths(create_osd_information(num_osds, osd_bandwidths))
+        distribution.set_osd_capacities(create_osd_information(num_osds, osd_capacities))
+
+        distribution.add_folders(create_test_folder_list(num_folders, folder_sizes))
+
+        self.assertEqual(8, distribution.get_maximum_processing_time()[1])
+
 
 def create_test_osd_list(num_osds, osd_capacities):
     test_osds = []

xtreemfs_client/dataDistribution.py

@@ -184,6 +184,26 @@ class DataDistribution(object):
                 maximum_osd = osd
         return maximum_osd, maximum_processing_time
 
+    def get_lower_bound_on_makespan(self):
+        total_remaining_file_size = self.get_total_folder_size()
+        artificial_data_distribution = copy.deepcopy(self)
+        for tmp_osd in artificial_data_distribution.OSDs.values():
+            for a_folder in list(tmp_osd.folders.keys()):
+                tmp_osd.remove_folder(a_folder)
+
+        while total_remaining_file_size > 0:
+            free_OSDs = list(filter(lambda x: x.get_free_capacity() > 0, artificial_data_distribution.OSDs.values()))
+            total_bandwidth = sum(list(map(lambda x: x.bandwidth, free_OSDs)))
+            assigned_file_size = 0
+            for free_OSD in free_OSDs:
+                optimal_share = (free_OSD.bandwidth / total_bandwidth) * total_remaining_file_size
+                assignable_share = min(optimal_share, free_OSD.get_free_capacity())
+                free_OSD.add_folder("dummy_id", assignable_share)
+                assigned_file_size += assignable_share
+            total_remaining_file_size -= assigned_file_size
+
+        return artificial_data_distribution.get_maximum_processing_time()[1]
+
     def add_folders(self, folders,
                     ignore_osd_capacities=True,
                     random_osd_assignment=False,

xtreemfs_client/osd.py

@@ -50,6 +50,9 @@ class OSD(object):
     def get_load(self):
         return self.total_folder_size
 
+    def get_free_capacity(self):
+        return self.capacity - self.total_folder_size
+
     def get_processing_time(self):
         return self.total_folder_size / self.bandwidth