diff --git a/PowerDiagram.py b/PowerDiagram.py
index 9b19253..72b5a31 100644
--- a/PowerDiagram.py
+++ b/PowerDiagram.py
@@ -41,6 +41,7 @@ class Machine(object):
         self.current_capacity_constraint = None  # the maximum amperes in this connection
         self.power_config = power_config
         self.power_consumption = 0.0
+        self.rack_id = None
 
     def get_plug(self, plug_name):
         plugs = {'i': self.input_plugs, 'o': self.output_plugs}[plug_name[0]]
@@ -199,6 +200,14 @@ class PowerConfig(object):
 
             machine_name = machine.name
 
+            # find its rack location
+            try:
+                rack_id, rack_slot_index = inventory.get_machine_rack_location(machine_name)
+                machine.rack_id = rack_id
+                machine.rack_slot_index = rack_slot_index
+            except SimpaDbUtil.TableAttrNotFound:
+                pass
+
             if re.match('[a-z]+.._..', machine_name):
                 # machine_name is a group of machines such as physix80_83
                 # in this case, we use a hack : the type and power consumption is based on the first machine of this group (in this example physix80)
@@ -220,6 +229,7 @@ class PowerConfig(object):
                 if power_consumption is not None:
                     machine.power_consumption = power_consumption
 
+
     def get_connection_to(self, to_plug):
         for connection in self.connections:
             if connection.to_plug == to_plug:
@@ -261,6 +271,7 @@ def power_config_to_svg(power_config, svg_file_path):
     graph = pygraphviz.AGraph()
     graph.graph_attr['overlap'] = 'false'
     graph.graph_attr['splines'] = 'true'
+    graph.graph_attr['rankdir'] = 'LR'  # to get hrizontal tree rather than vertical
     
     graph.edge_attr['colorscheme'] = 'rdylgn9'  # 'brbg11'
     graph.node_attr['shape'] = 'box'
@@ -280,6 +291,31 @@ def power_config_to_svg(power_config, svg_file_path):
     # graph.add_node('b')
     # graph.add_edge(u'a',u'b',color='blue')
     # graph.add_edge(u'b',u'a',color='blue')
+    racks = {}
+
+    for con in power_config.connections:
+        for machine in [con.from_plug.machine, con.to_plug.machine]:
+            rack_id = machine.rack_id
+            if rack_id is not None:
+                if rack_id not in racks.keys():
+                    rack = {}
+                    rack['name'] = rack_id
+                    rack['machines'] = []
+                    racks[rack_id] = rack
+                rack = racks[rack_id]
+                if machine.name not in rack['machines']:
+                    rack['machines'].append(machine)
+
+    if False:
+        x = 0.0
+        for rack in racks.itervalues():
+            y = 0.0
+            for machine in rack['machines']:
+                graph.add_node(machine.name, pos='%f,%f!' % (x, y))  # https://observablehq.com/@magjac/placing-graphviz-nodes-in-fixed-positions
+                print(machine.name, x, y)
+                y += 1.0
+            x += 1.0
+
     for con in power_config.connections:
         # print(con.from_plug.machine.name, con.to_plug.machine.name)
         if not con.is_redundancy_cable():  # don't display redundancy cables, as they might overlap and hide the main one
@@ -306,5 +342,19 @@ def power_config_to_svg(power_config, svg_file_path):
             # color='//%d' % int(9.0-amperes/capacity*8)
             
             graph.add_edge(con.from_plug.machine.name, con.to_plug.machine.name, color=color, label=label, penwidth=penwidth)
-    graph.layout(prog='twopi')
+
+    if True:
+        for rack_id, rack in racks.iteritems():
+            # sub = graph.add_subgraph(rack, name='cluster_%s' % rack_id, rank='same')
+            machine_names = list(machine.name for machine in rack['machines'])
+            sub = graph.add_subgraph(machine_names, name='cluster_%s' % rack_id)
+            sub.graph_attr['label'] = rack_id
+            # sub.graph_attr['rank']='same'
+    # assert False
+    #graph.layout(prog='twopi')
+    with open('./toto.dot', 'w') as f:
+        f.write(graph.string())
+
+
+    graph.layout(prog='dot')
     graph.draw(svg_file_path)
diff --git a/inventory.py b/inventory.py
index 0c96e5a..4d3a4e7 100644
--- a/inventory.py
+++ b/inventory.py
@@ -130,6 +130,11 @@ class Inventory(object):
         ordering_date = datetime.datetime.strptime(ordering_date_as_str, '%d/%m/%Y')
         return ordering_date
 
+    def get_machine_rack_location(self, machine_id):
+        rack_id = self._sql_reader.get_table_attr('rackable_machine_to_location', 'machine_id', machine_id, 'rack_id')
+        slot_index = self._sql_reader.get_table_attr('rackable_machine_to_location', 'machine_id', machine_id, 'slot_index')
+        return rack_id, slot_index
+
     def get_cpu_dflops(self, cpu_model):
         '''
         returns the number of double precision operation per second this cpu can achieve