From 5be13d35420ee7f94612c2193ed43c0e49383579 Mon Sep 17 00:00:00 2001
From: Jean-Baptiste Keck <Jean-Baptiste.Keck@imag.fr>
Date: Wed, 15 Apr 2020 21:09:39 +0200
Subject: [PATCH] remove graph_tool dependency in favor of networkx

---
 hysop/core/graph/computational_graph.py       | 158 ++-----
 hysop/core/graph/graph.py                     | 129 +++++-
 hysop/core/graph/graph_builder.py             | 384 +++++-------------
 hysop/operator/tests/test_absorption.py       |   2 +-
 .../tests/test_spectral_derivative.py         |   2 +-
 hysop/problem.py                              |  16 +-
 6 files changed, 261 insertions(+), 430 deletions(-)

diff --git a/hysop/core/graph/computational_graph.py b/hysop/core/graph/computational_graph.py
index 233f4e307..6aaffae39 100644
--- a/hysop/core/graph/computational_graph.py
+++ b/hysop/core/graph/computational_graph.py
@@ -7,7 +7,7 @@ from hysop.tools.string_utils import framed_str, strlen, multiline_split
 from hysop.tools.numpywrappers import npw
 from hysop.core.graph.graph import not_implemented, initialized, discretized, \
     ready, graph_built, not_initialized
-from hysop.core.graph.graph import Graph, ComputationalGraphNodeData, gt
+from hysop.core.graph.graph import ComputationalGraphNodeData
 from hysop.core.graph.computational_node import ComputationalGraphNode
 from hysop.core.graph.computational_operator import ComputationalGraphOperator
 from hysop.core.graph.node_generator import ComputationalGraphNodeGenerator
@@ -353,16 +353,12 @@ class ComputationalGraph(ComputationalGraphNode):
         return u'\n{}\n'.format(framed_str(title=title, msg=ss[1:]))
 
     def variable_report(self):
-        reduced_graph = self.reduced_graph
-        operators = reduced_graph.vertex_properties['operators']
         fields = self.fields
 
         topologies = {}
         for field in self.fields:
             field_topologies = {}
-            for (i, vid) in enumerate(self.sorted_nodes):
-                vertex = reduced_graph.vertex(vid)
-                op = operators[vertex]
+            for (i, node) in enumerate(self.nodes):
                 if field in op.input_fields:
                     topo = op.input_fields[field]
                     field_topologies.setdefault(topo, []).append(op)
@@ -420,43 +416,39 @@ class ComputationalGraph(ComputationalGraphNode):
         replace = ('--',  '',  '',  '-',  '',  '')
 
         reduced_graph = self.reduced_graph
-        operators = reduced_graph.vertex_properties['operators']
         ops = []
-        for (i, vid) in enumerate(self.sorted_nodes):
-            vertex = reduced_graph.vertex(vid)
-            op = operators[vertex]
-
+        for (i, node) in enumerate(self.nodes):
             handled_inputs, handled_outputs = (), ()
             finputs, foutputs = [], []
-            for f in op.input_tensor_fields:
+            for f in node.input_tensor_fields:
                 f0 = f.fields[0]
-                t0 = op.input_fields[f0]
-                if all((op.input_fields[fi] is t0) for fi in f.fields):
+                t0 = node.input_fields[f0]
+                if all((node.input_fields[fi] is t0) for fi in f.fields):
                     finputs.append(u'{}.{}'.format(f.pretty_name.decode('utf-8'),
                                                    t0.pretty_tag.decode('utf-8')))
                     handled_inputs += f.fields
-            for f in op.output_tensor_fields:
+            for f in node.output_tensor_fields:
                 f0 = f.fields[0]
-                t0 = op.output_fields[f0]
-                if all((op.output_fields[fi] is t0) for fi in f.fields):
+                t0 = node.output_fields[f0]
+                if all((node.output_fields[fi] is t0) for fi in f.fields):
                     foutputs.append(u'{}.{}'.format(f.pretty_name.decode('utf-8'),
                                                     t0.pretty_tag.decode('utf-8')))
                     handled_outputs += f.fields
             finputs += [u'{}.{}'.format(f.pretty_name.decode('utf-8'),
                                         t.pretty_tag.decode('utf-8'))
-                        for (f, t) in op.input_fields.iteritems()
+                        for (f, t) in node.input_fields.iteritems()
                         if f not in handled_inputs]
             foutputs += [u'{}.{}'.format(f.pretty_name.decode('utf-8'),
                                          t.pretty_tag.decode('utf-8'))
-                         for (f, t) in op.output_fields.iteritems()
+                         for (f, t) in node.output_fields.iteritems()
                          if f not in handled_outputs]
             finputs = u','.join(sorted(finputs))
             foutputs = u','.join(sorted(foutputs))
 
             pinputs = u','.join(sorted([p.pretty_name.decode('utf-8')
-                                        for p in op.input_params.values()]))
+                                        for p in node.input_params.values()]))
             poutputs = u','.join(sorted([p.pretty_name.decode('utf-8')
-                                         for p in op.output_params.values()]))
+                                         for p in node.output_params.values()]))
 
             infields = u'[{}]'.format(finputs) if finputs else u''
             outfields = u'[{}]'.format(foutputs) if foutputs else u''
@@ -471,8 +463,8 @@ class ComputationalGraph(ComputationalGraphNode):
             if outputs == '':
                 outputs = u'no outputs'
 
-            opname = op.pretty_name.decode('utf-8')
-            optype = type(op).__name__
+            opname = node.pretty_name.decode('utf-8')
+            optype = type(node).__name__
             strdata = (str(i), opname, inputs, '->', outputs, optype)
 
             ops += multiline_split(strdata, maxlen, split_sep, replace, newline_prefix)
@@ -626,11 +618,8 @@ class ComputationalGraph(ComputationalGraphNode):
     def check(self):
         super(ComputationalGraph, self).check()
         reduced_graph = self.reduced_graph
-        operators = reduced_graph.vertex_properties['operators']
-        for vid in self.sorted_nodes:
-            vertex = reduced_graph.vertex(vid)
-            op = operators[vertex]
-            op.check()
+        for node in self.nodes:
+            node.check()
 
     @debug
     def get_field_requirements(self):
@@ -722,66 +711,16 @@ class ComputationalGraph(ComputationalGraphNode):
         from hysop import main_rank
         if (visu_rank is None) or (main_rank != visu_rank):
             return
-
-        graph = self.reduced_graph
-        edge_text = graph.edge_properties['var_names']
-        vertex_text = graph.vertex_properties['op_pnames']
-        vertex_info = graph.vertex_properties['op_info']
-        if 'command_queues' in graph.vp:
-            command_queues = graph.vertex_properties['command_queues']
-            active_ops = graph.vertex_properties['active_ops']
-        else:
-            command_queues = None
-            active_ops = None
-
-        def draw():
-            import time
-            from gi.repository import Gtk, GObject
-            from graph_tool.draw import GraphWindow, sfdp_layout
-
-            pos_layout = sfdp_layout(graph)
-
-            win = GraphWindow(graph, pos_layout, geometry=(800, 600),
-                              vertex_text=vertex_text,
-                              edge_text=edge_text,
-                              vertex_font_size=vertex_font_size,
-                              edge_font_size=edge_font_size,
-                              vertex_color=active_ops,
-                              vertex_fill_color=command_queues,
-                              display_props=vertex_info,
-                              display_props_size=14,
-                              max_render_time=50)
-
-            def update_window():
-                win.graph.regenerate_surface()
-                win.graph.queue_draw()
-                time.sleep(0.01)
-                return True
-
-            GObject.idle_add(update_window)
-            win.connect("delete_event", Gtk.main_quit)
-            win.show_all()
-            Gtk.main()
-            self.graph_is_rendering = False
-
-        self.graph_is_rendering = True
-
-        from threading import Thread
-        display_thread = Thread(target=draw)
-        display_thread.start()
+        raise NotImplementedError('This feature has not been implemented yet.')
 
     @debug
     @graph_built
     def discretize(self):
         if self.discretized:
             return
-        reduced_graph = self.reduced_graph
-        operators = reduced_graph.vertex_properties['operators']
-        for vid in self.sorted_nodes:
-            vertex = reduced_graph.vertex(vid)
-            op = operators[vertex]
-            if not op.discretized:
-                op.discretize()
+        for node in self.nodes:
+            if not node.discretized:
+                node.discretize()
 
         if self.is_root:
             input_discrete_fields = {}
@@ -846,14 +785,10 @@ class ComputationalGraph(ComputationalGraphNode):
     def get_work_properties(self):
         requests = MultipleOperatorMemoryRequests()
 
-        reduced_graph = self.reduced_graph
-        operators = reduced_graph.vertex_properties['operators']
-        for vid in self.sorted_nodes:
-            vertex = reduced_graph.vertex(vid)
-            op = operators[vertex]
-            if op not in requests.operators():
-                wp = op.get_work_properties()
-                requests += op.get_work_properties()
+        for node in self.nodes:
+            if node not in requests.operators():
+                wp = node.get_work_properties()
+                requests += node.get_work_properties()
         if __DEBUG__ or (__VERBOSE__ and self.level == 0) or self.__FORCE_REPORTS__:
             srequests = requests.sreport()
             ss = (srequests if (srequests != u'') else u' *no extra work requested*')
@@ -870,13 +805,9 @@ class ComputationalGraph(ComputationalGraphNode):
         if (work is None):
             work = self.get_work_properties()
             work.allocate(allow_subbuffers=allow_subbuffers)
-        reduced_graph = self.reduced_graph
-        operators = reduced_graph.vertex_properties['operators']
-        for vid in self.sorted_nodes:
-            vertex = reduced_graph.vertex(vid)
-            op = operators[vertex]
-            if not op.ready:
-                op.setup(work=work)
+        for node in self.nodes:
+            if not node.ready:
+                node.setup(work=work)
         self.ready = True
 
     def build(self, outputs_are_inputs=True, method=None, allow_subbuffers=False):
@@ -896,38 +827,17 @@ class ComputationalGraph(ComputationalGraphNode):
     @debug
     @ready
     def apply(self, **kwds):
-        drawing = self.graph_is_rendering
-        reduced_graph = self.reduced_graph
-        operators = reduced_graph.vertex_properties['operators']
-
-        if drawing:
-            active_ops = reduced_graph.vertex_properties['active_ops']
-            old_color = None
-            for vid in self.sorted_nodes:
-                if old_color:
-                    active_ops[vertex] = old_color
-                vertex = reduced_graph.vertex(vid)
-                old_color = active_ops[vertex]
-                active_ops[vertex] = 'red'
-                op = operators[vertex]
-                dprint('{}.apply()'.format(op.name))
-                op.apply(**kwds)
-                active_ops[vertex] = old_color
-        else:
-            for op in self.nodes:
-                dprint('{}.apply()'.format(op.name))
-                op.apply(**kwds)
+        for node in self.nodes:
+            dprint('{}.apply()'.format(node.name))
+            node.apply(**kwds)
 
     @debug
     @ready
     def finalize(self, **kwds):
         reduced_graph = self.reduced_graph
-        operators = reduced_graph.vertex_properties['operators']
-        for vid in self.sorted_nodes:
-            vertex = reduced_graph.vertex(vid)
-            op = operators[vertex]
-            if op.ready:
-                op.finalize(**kwds)
+        for node in self.nodes:
+            if node.ready:
+                node.finalize(**kwds)
         self.ready = False
 
     @classmethod
diff --git a/hysop/core/graph/graph.py b/hysop/core/graph/graph.py
index 09e5a7f57..6c2f37aff 100644
--- a/hysop/core/graph/graph.py
+++ b/hysop/core/graph/graph.py
@@ -1,11 +1,79 @@
-import inspect
-import graph_tool as gt
-from graph_tool import Graph, GraphView
-from graph_tool import topology, stats, search
-from hysop.tools.decorators import not_implemented, debug, wraps, profile
+import inspect, networkx
 from hysop import dprint
+from hysop.tools.types import check_instance, first_not_None
+from hysop.tools.decorators import not_implemented, debug, wraps, profile
+
+is_directed_acyclic_graph = networkx.algorithms.dag.is_directed_acyclic_graph
+transitive_reduction = networkx.algorithms.dag.transitive_reduction
+
+def all_simple_paths(graph, src, dst):
+    return tuple(networkx.algorithms.simple_paths.all_simple_paths(graph, src, dst))
+
+def topological_sort(graph):
+    return tuple(networkx.algorithms.dag.topological_sort(graph))
+
+def new_directed_graph():
+    return networkx.DiGraph()
+
+def new_vertex(graph, *args, **kwds):
+    # /!\ We have to use networkx 2.2 which has a different interface for attributes
+    node = VertexAttributes(graph, *args, **kwds)
+    graph.add_node(node)
+    return node
 
+def new_edge(graph, u, v, *args, **kwds):
+    # /!\ We have to use networkx 2.2 which has a different interface for attributes
+    graph.add_edge(u, v, object=EdgeAttributes(*args, **kwds))
+    return (u,v)
+        
+class VertexAttributes(object):
+    """Simple class to hold vertex data."""
+    def __init__(self, graph, operator=None):
+        if not hasattr(graph, '_hysop_node_counter'):
+            graph._hysop_node_counter = 0
+        node_id = graph._hysop_node_counter
+        graph._hysop_node_counter += 1
+        
+        self.node_id  = node_id
+        self.operator = operator
+        
+        self.input_states  = None
+        self.output_states = None
+        self.op_ordering   = None
+        self.command_queue = None
 
+    def copy_attributes(self, other):
+        if (other is None):
+            return self
+        check_instance(other, VertexAttributes)
+        for vname in ('operator', 
+                      'input_states', 'output_states', 
+                      'op_ordering', 'command_queue'):
+            setattr(self, vname, first_not_None(getattr(self,  vname), 
+                                                getattr(other, vname)))
+        return self
+
+    def set_op_info(self, operator, input_states, output_states):
+        assert (self.operator is not None)
+        assert self.operator is operator
+        self.operator      = operator
+        self.input_states  = input_states
+        self.output_states = output_states
+        return self
+    
+    def hash(self):
+        return self.node_id
+    def __eq__(self, other):
+        return self.node_id == other.node_id
+    def __int__(self):
+        return self.node_id
+
+class EdgeAttributes(object):
+    """Simple class to hold edge data."""
+    def __init__(self, variable=None, topology=None):
+        self.variable = variable
+        self.topology = topology
+    
 class ComputationalGraphNodeData(object):
     """
     Simple class to hold some node data.
@@ -127,7 +195,6 @@ def op_apply(f):
     @profile
     @ready
     def apply(*args, **kwds):
-        #print u'APPLY {}'.format(args[0].name)
         dbg = ('dbg' in kwds)
         dbg = dbg and (kwds['dbg'] is not None)
         dbg = dbg and (kwds['dbg'].enable_on_op_apply)
@@ -175,3 +242,53 @@ def op_apply(f):
                 return
         return ret
     return apply
+
+def _op_info(op, istates=None, ostates=None, jmp=False):
+    ifields = op.input_fields
+    ofields = op.output_fields
+    iparams = op.input_params
+    oparams = op.output_params
+
+    memorder2str = {
+            MemoryOrdering.C_CONTIGUOUS: 'C',
+            MemoryOrdering.F_CONTIGUOUS: 'F',
+    }
+
+    def ifinfo(field, topo):
+        info = (field.name, topo.id)
+        if istates:
+            assert field in istates
+            istate = istates[field]
+            assert (istate is not None)
+            info+=(memorder2str[istate.memory_order],)
+            info+=(str(istate.tstate),)
+        return info
+    def ofinfo(field, topo):
+        info = (field.name, topo.id)
+        if ostates:
+            assert field in ostates
+            ostate = ostates[field]
+            assert (ostate is not None)
+            info+=(memorder2str[ostate.memory_order],)
+            info+=(str(ostate.tstate),)
+        return info
+    def ipinfo(param):
+        return param.name
+    def opinfo(param):
+        return param.name
+
+    ss = 'Operator {} => \n {}{}{}{}\n  {}'.format(op.name,
+            'Pin:{}\n  '.format([ ipinfo(param) for param in iparams.values() ])
+                if iparams else '',
+            'Fin:{}\n  '.format([ ifinfo(f,topo) for (f,topo) in ifields.iteritems() ])
+                if ifields else '',
+            'Pout:{}\n  '.format([ opinfo(param) for param in oparams.values() ])
+                if oparams else '',
+            'Fout:{}\n  '.format([ ofinfo(f,topo) for (f,topo) in ofields.iteritems() ])
+                if ofields else '',
+            op.__class__)
+    if jmp:
+        return ss
+    else:
+        return ss.replace('\n','    ')
+
diff --git a/hysop/core/graph/graph_builder.py b/hysop/core/graph/graph_builder.py
index 3abe3a7ef..5cda50bcc 100644
--- a/hysop/core/graph/graph_builder.py
+++ b/hysop/core/graph/graph_builder.py
@@ -1,3 +1,4 @@
+
 from hysop import vprint, dprint, Problem
 from hysop.deps import np, __builtin__, print_function
 from hysop.tools.types import check_instance
@@ -9,16 +10,21 @@ from hysop.constants import MemoryOrdering, Backend
 from hysop.parameters.parameter import Parameter
 from hysop.topology.cartesian_topology import CartesianTopologyState
 
+from hysop.core.graph.graph import (new_directed_graph, new_vertex, new_edge,
+                                    is_directed_acyclic_graph, transitive_reduction,
+                                    topological_sort, all_simple_paths)
 from hysop.core.graph.computational_graph    import ComputationalGraph
 from hysop.core.graph.computational_node     import ComputationalGraphNode
 from hysop.core.graph.computational_operator import ComputationalGraphOperator
-from hysop.core.graph.graph import Graph, ComputationalGraphNodeData, gt
 
-from hysop.fields.field_requirements import DiscreteFieldRequirements, MultiFieldRequirements
+from hysop.fields.field_requirements import (DiscreteFieldRequirements, 
+                                             MultiFieldRequirements)
 
-from hysop.operator.redistribute      import Redistribute, RedistributeNotImplementedError
-from hysop.operator.transpose         import Transpose, TranspositionNotImplementedError
-from hysop.operator.memory_reordering import MemoryReordering, MemoryReorderingNotImplementedError
+from hysop.operator.redistribute import (Redistribute,
+                                         RedistributeNotImplementedError)
+from hysop.operator.transpose import Transpose, TranspositionNotImplementedError
+from hysop.operator.memory_reordering import (MemoryReordering,
+                                              MemoryReorderingNotImplementedError)
 
 # Debug level for graph building
 #   0: no debug logs
@@ -35,57 +41,6 @@ def gprint2(*args, **kwds):
     kwds['level'] = 2
     gprint(*args, **kwds)
 
-def _op_info(op,
-        istates=None, ostates=None,
-        jmp=False):
-    ifields = op.input_fields
-    ofields = op.output_fields
-    iparams = op.input_params
-    oparams = op.output_params
-
-    memorder2str = {
-            MemoryOrdering.C_CONTIGUOUS: 'C',
-            MemoryOrdering.F_CONTIGUOUS: 'F',
-    }
-
-    def ifinfo(field, topo):
-        info = (field.name, topo.id)
-        if istates:
-            assert field in istates
-            istate = istates[field]
-            assert (istate is not None)
-            info+=(memorder2str[istate.memory_order],)
-            info+=(str(istate.tstate),)
-        return info
-    def ofinfo(field, topo):
-        info = (field.name, topo.id)
-        if ostates:
-            assert field in ostates
-            ostate = ostates[field]
-            assert (ostate is not None)
-            info+=(memorder2str[ostate.memory_order],)
-            info+=(str(ostate.tstate),)
-        return info
-    def ipinfo(param):
-        return param.name
-    def opinfo(param):
-        return param.name
-
-    ss = 'Operator {} => \n {}{}{}{}\n  {}'.format(op.name,
-            'Pin:{}\n  '.format([ ipinfo(param) for param in iparams.values() ])
-                if iparams else '',
-            'Fin:{}\n  '.format([ ifinfo(f,topo) for (f,topo) in ifields.iteritems() ])
-                if ifields else '',
-            'Pout:{}\n  '.format([ opinfo(param) for param in oparams.values() ])
-                if oparams else '',
-            'Fout:{}\n  '.format([ ofinfo(f,topo) for (f,topo) in ofields.iteritems() ])
-                if ofields else '',
-            op.__class__)
-    if jmp:
-        return ss
-    else:
-        return ss.replace('\n','    ')
-
 
 class GraphBuilder(object):
     """
@@ -126,21 +81,7 @@ class GraphBuilder(object):
         gprint(msg)
 
     def setup_graph(self):
-        graph = Graph(directed=True)
-
-        vertex_properties = {}
-        vertex_properties['op_names']  = graph.new_vertex_property('string')
-        vertex_properties['op_pnames']  = graph.new_vertex_property('string')
-        vertex_properties['op_info']   = graph.new_vertex_property('string')
-        vertex_properties['operators'] = graph.new_vertex_property('python::object')
-
-        edge_properties = {}
-        edge_properties['var_names'] = graph.new_edge_property('string')
-        edge_properties['variables'] = graph.new_edge_property('python::object')
-
-        self.graph = graph
-        self.vertex_properties = vertex_properties
-        self.edge_properties = edge_properties
+        self.graph = new_directed_graph()
 
     def setup_variables(self):
         self.input_fields = {}
@@ -160,40 +101,23 @@ class GraphBuilder(object):
                 self.target_node._input_fields_to_dump,
                 self.target_node.method)
 
-    def new_node(self, opname, oppname, op, subgraph,
-            current_level, node, node_id,
-            extra_node_props, opvertex):
-        graph = self.graph
-        vertex_properties = self.vertex_properties
+    def new_node(self, op, subgraph,
+            current_level, node, node_id, opvertex):
 
-        opnode  = graph.add_vertex()
-        vertex_properties['op_names'][opnode]  = opname
-        vertex_properties['op_pnames'][opnode]  = oppname
-        vertex_properties['operators'][opnode] = op
+        graph = self.graph
+        opnode = new_vertex(graph, op).copy_attributes(opvertex)
         gprint('  *Created node is {}.'.format(int(opnode)))
-
-        if opvertex:
-            assert (extra_node_props is not None)
-            assert 'op_info' in extra_node_props
-            level = node.level + 1
-            for enp in extra_node_props:
-                vertex_properties[enp][opnode] = subgraph.vp[enp][opvertex]
-        else:
-            level = current_level
         return opnode
 
     def build_graph(self):
-
         target_node = self.target_node
 
         current_level = self.current_level
         outputs_are_inputs = self.outputs_are_inputs
 
         graph = self.graph
-        vertex_properties = self.vertex_properties
-        edge_properties = self.edge_properties
 
-        parameter_handler = self.__ParameterHandler(graph, edge_properties, vertex_properties)
+        parameter_handler = self.__ParameterHandler(graph)
 
         input_fields = self.input_fields
         output_fields = self.output_fields
@@ -230,7 +154,7 @@ class GraphBuilder(object):
             # build its own local graph and we extract all its operators (graph nodes).
             # Else if node is a ComputationalGraphOperator, we just take the
             # current node operator.
-            subgraph, node_ops, node_vertices, from_subgraph, extra_node_props = \
+            subgraph, node_ops, node_vertices, from_subgraph = \
                     self.build_subgraph(node, current_level)
 
             # iterate over subgraph operators
@@ -245,9 +169,8 @@ class GraphBuilder(object):
                 field_requirements = op._field_requirements
 
                 # add operator node and fill vertex properties
-                opnode = self.new_node(opname, oppname, op, subgraph,
-                        current_level, node, node_id,
-                        extra_node_props, opvertex)
+                opnode = self.new_node(op, subgraph,
+                        current_level, node, node_id, opvertex)
 
                 if not isinstance(op, Problem):
                     # try to fill in undertermined topologies (experimental feature)
@@ -342,8 +265,7 @@ class GraphBuilder(object):
                             is_new = False
 
                         dstate = cstate.handle_input(opnode, itopo, ifreqs,
-                                    graph, edge_properties, vertex_properties,
-                                    is_new)
+                                    graph, is_new)
                         input_states[ifield] = dstate
 
                         if is_new:
@@ -370,15 +292,13 @@ class GraphBuilder(object):
                                                 self.new_topology_state(ofield))
                         invalidate_field = (ofield not in op.get_preserved_input_fields())
                         dstate = cstate.handle_output(opnode, otopo, ofreqs,
-                                    op, istates, invalidate_field,
-                                    graph, edge_properties, vertex_properties)
+                                    op, istates, invalidate_field, graph)
                         output_fields[ofield] = otopo
                         output_states[ofield] = dstate
                         output_topology_states[ofield] = (None, dstate)
 
                 if (current_level==0) and ((op,opnode) not in deferred_operators):
-                    vertex_properties['op_info'][opnode] = _op_info(op, input_states,
-                            output_states)
+                    opnode.set_op_info(op, input_states, output_states)
 
                 op_input_topology_states[op]  = input_states
                 op_output_topology_states[op] = output_states
@@ -408,10 +328,9 @@ class GraphBuilder(object):
                 ifields[ifield] = itopo
                 input_states[ifield] = dstate
                 field_requirements.update_inputs({ifield: ireqs})
-                cstate.add_edge(graph, edge_properties, opnode, node, ifield, itopo)
+                cstate.add_edge(graph, opnode, node, ifield, itopo)
             if current_level==0:
-                vertex_properties['op_info'][opnode] = _op_info(op, input_states,
-                        output_states)
+                opnode.set_op_info(op, input_states, output_states)
 
         if current_level==0:
             msg='\nComputationalGraph {} inputs:\n'.format(target_node.name)
@@ -455,20 +374,18 @@ class GraphBuilder(object):
                             **op_kwds)
                     op.initialize(topgraph_method=self.target_node.method)
                     op.get_and_set_field_requirements()
-                    opnode = self.new_node(opname, oppname, op, None,
-                            current_level, None, None, None, None)
+                    opnode = self.new_node(op, None, current_level, 
+                            None, None, None, None)
                     ifreqs = None if (current_level!=0) \
                                   else field_requirements.get_input_requirement(field)[1]
                     cstate = self.topology_states[field]
-                    state = cstate.handle_input(opnode, target_topo, ifreqs,
-                            graph, edge_properties, vertex_properties, False)
+                    state = cstate.handle_input(opnode, target_topo, ifreqs, graph,False)
                     input_states  = {field: state}
                     output_states = {}
                     self.op_input_topology_states[op]  = input_states
                     self.op_output_topology_states[op] = output_states
                     if current_level==0:
-                        vertex_properties['op_info'][opnode] = _op_info(op, input_states,
-                                output_states)
+                        opnode.set_op_info(op, input_states, output_states)
 
         # Alter states such that output topology states match input topology states
         # this is only done if required (outputs_are_inputs) and if we are
@@ -487,118 +404,68 @@ class GraphBuilder(object):
                 requirements.memory_order = input_topology_state.memory_order
 
                 cstate = self.topology_states[field]
-                cstate.output_as_input(target_topo, requirements,
-                        graph, edge_properties, vertex_properties)
+                cstate.output_as_input(target_topo, requirements, graph)
 
         # Check that the generated graph is a directed acyclic graph
-        if not gt.topology.is_DAG(graph):
+        if not is_directed_acyclic_graph(graph):
             msg='\nGenerated operator graph is not acyclic.'
-            print(msg)
-
-            #display graph for debug purposes
-            gt.stats.remove_parallel_edges(graph)
-            for prop_name,edge_property in edge_properties.iteritems():
-                graph.edge_properties[prop_name] = edge_property
-            for prop_name,vertex_property in vertex_properties.iteritems():
-                if prop_name != 'command_queues':
-                    graph.vertex_properties[prop_name] = vertex_property
-            target_node.graph_built = True
-            target_node.reduced_graph = graph
-            target_node.display()
-
-            # and finally raise error
             raise RuntimeError(msg)
 
-        # Transitive reduction of graph (remove parallel and unnecessary transitive edges)
+        # Transitive reduction of graph 
+        # This removes parallel and unnecessary transitive edges
         # ie. remove useless redondant dependencies
-        transitive_reduction = gt.stats.label_parallel_edges(graph, mark_only=True,
-                    eprop = graph.new_edge_property('bool',val=False))
-        for vertex in graph.vertices():
-            for neighbor_vertex in vertex.out_neighbours():
-                accessible_vertices = \
-                        [v for v in gt.search.dfs_iterator(graph, neighbor_vertex)]
-                for edge in accessible_vertices:
-                    edge = graph.edge(vertex, edge.target())
-                    if edge is not None:
-                        transitive_reduction[edge] = True
-        transitive_reduction.a = [ not val for val in transitive_reduction.get_array()]
-        reduced_graph = gt.GraphView(graph, efilt = transitive_reduction)
+        reduced_graph = transitive_reduction(graph)
 
         # Topological sort
         # ie. find out operator order for execution purposes
-        sorted_nodes = gt.topology.topological_sort(reduced_graph)
-        vertex_properties['op_ordering']  = reduced_graph.new_vertex_property('int')
-        for i,node_id in enumerate(sorted_nodes):
-            vertex = reduced_graph.vertex(node_id)
-            vertex_properties['op_ordering'][vertex] = i
-            if current_level==0:
-                vertex_properties['op_names'][vertex] += ' ('+str(i)+')'
-                vertex_properties['op_pnames'][vertex] += ' ('+str(i)+')'
+        sorted_nodes = topological_sort(reduced_graph)
+        for (i, node) in enumerate(sorted_nodes):
+            node.op_ordering = i
 
         # Command queues (each color represents a command queue)
         # ie. try to find out data independent subgraphs
         color = 0
         queues = {}
-        vertex_properties['command_queues'] = graph.new_vertex_property('int',val=-1)
-        vertex_properties['active_ops'] = graph.new_vertex_property('string',val='darkgray')
-        for vertex_id in sorted_nodes:
-            vertex = reduced_graph.vertex(vertex_id)
-            if (vertex_properties['command_queues'][vertex] >= 0):
+        for node in sorted_nodes:
+            if (node.command_queue is not None):
                 continue
 
-            vertices = [vertex]
-            uncolored_childs = [ v for v in vertex.out_neighbours() \
-                    if (vertex_properties['command_queues'][v] == -1) ]
+            nodes = [node]
+            uncolored_childs = tuple(filter(lambda n: n.command_queue is None, 
+                                            reduced_graph.adj[node]))
             while len(uncolored_childs)>0:
-                vid  = np.argmin( [vertex_properties['op_ordering'][v]
-                    for v in uncolored_childs] )
-                vertex = uncolored_childs[vid]
-                vertices.append(vertex)
-                uncolored_childs = [ v for v in vertex.out_neighbours() \
-                        if (vertex_properties['command_queues'][v] == -1) ]
+                vid  = np.argmin( [n.op_ordering for n in uncolored_childs] )
+                node = uncolored_childs[vid]
+                nodes.append(node)
+                uncolored_childs = tuple(filter(lambda n: n.command_queue is None, 
+                                                reduced_graph.adj[node]))
 
-            idx_range = (vertex_properties['op_ordering'][vertices[0]],
-                         vertex_properties['op_ordering'][vertices[-1]])
+            idx_range = (nodes[0].op_ordering, nodes[-1].op_ordering)
 
             if queues:
                 color = queues.keys()[-1]+1
-
                 for k in queues.keys()[::-1]:
                     paths = queues[k]
                     if (paths[-1][1] < idx_range[0]):
-                        src       = reduced_graph.vertex(sorted_nodes[paths[-1][1]])
-                        dst       = reduced_graph.vertex(sorted_nodes[idx_range[0]])
-                        all_paths = gt.topology.all_paths(reduced_graph,src,dst)
-                        all_paths = [p for p in all_paths]
+                        src       = sorted_nodes[paths[-1][1]]
+                        dst       = sorted_nodes[idx_range[0]]
+                        all_paths = all_simple_paths(reduced_graph,src,dst)
                         if len(all_paths)>0:
                             color = k
                             break
 
             queues.setdefault(color,[]).append(idx_range)
 
-            for vertex in vertices:
-                vertex_properties['command_queues'][vertex] = color
-
-        # bind all original graph properties to reduced graph
-        for prop_name,edge_property in edge_properties.iteritems():
-            reduced_graph.edge_properties[prop_name] = edge_property
-        for prop_name,vertex_property in vertex_properties.iteritems():
-            reduced_graph.vertex_properties[prop_name] = vertex_property
+            for node in nodes:
+                node.command_queue = color
 
         self.reduced_graph = reduced_graph
-        self.sorted_nodes = sorted_nodes
-        self.nodes = self._gather_nodes()
-
-    def _gather_nodes(self):
-        reduced_graph = self.reduced_graph
-        operators     = reduced_graph.vertex_properties['operators']
-        nodes = [ operators[reduced_graph.vertex(vid)] for vid in self.sorted_nodes ]
-        return nodes
+        self.sorted_nodes  = sorted_nodes
+        self.nodes = tuple(map(lambda x: x.operator, sorted_nodes))
 
     def build_subgraph(self, node, current_level, **kwds):
         node_ops = []
         node_vertices = []
-        extra_node_props = []
 
         subgraph = None
         from_subgraph = False
@@ -613,18 +480,11 @@ class GraphBuilder(object):
             node_ordering   = node.sorted_nodes
             subgraph        = node.reduced_graph
             from_subgraph   = True
-            subgraph_ops    = subgraph.vertex_properties['operators']
-            vertex_properties = None
             for nid in node_ordering:
-                _node = subgraph.vertex(nid)
-                op = subgraph_ops[_node]
+                _node = nid
+                op = _node.operator
                 node_vertices.append(_node)
                 node_ops.append(op)
-            for prop_name,vp in subgraph.vertex_properties.iteritems():
-                if prop_name not in self.vertex_properties:
-                    self.vertex_properties[prop_name] = \
-                            self.graph.new_vertex_property(vp.value_type())
-                extra_node_props.append(prop_name)
         elif isinstance(node, ComputationalGraphOperator):
             node_operators = node.operators()
             node_ops.extend(node_operators)
@@ -633,22 +493,19 @@ class GraphBuilder(object):
             msg = 'Unknown node type {}.'
             raise NotImplementedError(msg.format(node.__class__.__name__))
 
-        return subgraph, node_ops, node_vertices, from_subgraph, extra_node_props
+        return subgraph, node_ops, node_vertices, from_subgraph
 
 
     class __ParameterHandler(object):
-        def __init__(self, graph, edge_properties, vertex_properties):
+        def __init__(self, graph):
             self.graph = graph
-            self.edge_properties = edge_properties
-            self.vertex_properties = vertex_properties
             self.last_write_node = {}
             self.reading_nodes = {}
 
         def add_edge(self, src_node, dst_node, parameter):
             if (src_node is not None) and (dst_node is not None) \
                     and (src_node != dst_node):
-                edge = self.graph.add_edge(src_node, dst_node)
-                self.edge_properties['var_names'][edge] = parameter.pretty_name
+                edge = new_edge(self.graph, src_node, dst_node, parameter)
                 return edge
             else:
                 return None
@@ -720,30 +577,18 @@ class GraphBuilder(object):
 
             self.method = topgraph_method
 
-        def add_vertex(self, graph, vertex_properties, operator):
-            vertex = graph.add_vertex()
-            vertex_properties['operators'][vertex] = operator
-            vertex_properties['op_names'][vertex]  = operator.name
-            vertex_properties['op_pnames'][vertex]  = operator.pretty_name
-            #gprint('Creating vertex {}.'.format(int(vertex)))
-            return vertex
-
-        def add_edge(self, graph, edge_properties,
-                src_node, dst_node,
-                field, topology):
+        def add_vertex(self, graph, operator):
+            return new_vertex(graph, operator)
+
+        def add_edge(self, graph, src_node, dst_node, field, topology):
             if (src_node is not None) and (dst_node is not None) \
                     and (src_node != dst_node):
-                edge = graph.add_edge(src_node, dst_node)
-                edge_properties['var_names'][edge] = \
-                    '{}.{}'.format(field.pretty_name, topology.pretty_tag)
-                #gprint('Adding edge between {} and {}.'.format(int(src_node), int(dst_node)))
-                return edge
+                return new_edge(graph, src_node, dst_node, field, topology)
             else:
                 return None
 
-
         def push_generated_operators(self, op_generator, op_name_prefix,
-                src_topo, graph, vertex_properties, edge_properties):
+                src_topo, graph):
 
             field = self.field
             read_nodes = self.read_nodes
@@ -767,21 +612,17 @@ class GraphBuilder(object):
                 assert op.input_fields.values()[0] == src_topo
                 dst_topo = op.output_fields.values()[0]
 
-                op_node = self.add_vertex(graph, vertex_properties, op)
+                op_node = self.add_vertex(graph, op)
 
                 # handle input
                 if (src_topo in write_nodes):
                     src_node = write_nodes[src_topo]
-                    self.add_edge(graph, edge_properties,
-                            src_node, op_node,
-                            field, src_topo)
+                    self.add_edge(graph, src_node, op_node, field, src_topo)
 
                 # handle output
                 ro_nodes = read_nodes.setdefault(dst_topo, [])
                 for ro_node in ro_nodes:
-                    self.add_edge(graph, edge_properties,
-                            ro_node, op_node,
-                            field, dst_topo)
+                    self.add_edge(graph, ro_node, op_node, field, dst_topo)
 
                 read_nodes[dst_topo] = []
                 write_nodes[dst_topo] = op_node
@@ -798,17 +639,14 @@ class GraphBuilder(object):
                 op_input_topology_states[op]  = istate
                 op_output_topology_states[op] = ostate
 
-                vertex_properties['op_info'][op_node] = _op_info(op,
-                        istates=istate, ostates=ostate)
+                op_node.set_op_info(op, istate, ostate)
 
                 src_node = op_node
                 src_topo = dst_topo
 
             return dst_topo
 
-        def redistribute(self, target_topo,
-                graph, vertex_properties, edge_properties,
-                src_topo=None):
+        def redistribute(self, target_topo, graph, src_topo=None):
 
                 field = self.field
                 write_nodes = self.write_nodes
@@ -852,11 +690,10 @@ class GraphBuilder(object):
                 assert src_topo in src_topos
 
                 dst_topo = self.push_generated_operators(redistribute_generator, 'R',
-                        src_topo, graph, vertex_properties, edge_properties)
+                        src_topo, graph)
                 assert dst_topo == target_topo
 
-        def transpose(self, topo, target_axes,
-                graph, vertex_properties, edge_properties):
+        def transpose(self, topo, target_axes, graph):
                 
             field = self.field
             write_nodes = self.write_nodes
@@ -906,12 +743,11 @@ class GraphBuilder(object):
                 print('\n{}\n'.format(msg))
                 raise
 
-            dst_topo = self.push_generated_operators(transpose_generator, 'T', topo,
-                    graph, vertex_properties, edge_properties)
+            dst_topo = self.push_generated_operators(transpose_generator, 'T', 
+                    topo, graph)
             assert dst_topo == topo
 
-        def reorder(self, topo, target_memory_order,
-                graph, vertex_properties, edge_properties):
+        def reorder(self, topo, target_memory_order, graph):
 
             field = self.field
             write_nodes = self.write_nodes
@@ -946,12 +782,12 @@ class GraphBuilder(object):
                 print('\n{}\n'.format(msg))
                 raise
 
-            dst_topo = self.push_generated_operators(reorder_generator, 'MR', topo,
-                    graph, vertex_properties, edge_properties)
+            dst_topo = self.push_generated_operators(reorder_generator, 'MR', 
+                    topo, graph)
             assert dst_topo == topo
 
         def handle_input(self, opnode, target_topo, target_dfield_requirements,
-                graph, edge_properties, vertex_properties, is_new):
+                graph, is_new):
 
             ifield        = self.field
             write_nodes   = self.write_nodes
@@ -976,10 +812,8 @@ class GraphBuilder(object):
                         **op_kwds)
                 writer_op.initialize(topgraph_method=self.method)
                 writer_op.get_and_set_field_requirements()
-                writer_opnode = self.add_vertex(graph, vertex_properties, writer_op)
-                self.add_edge(graph, edge_properties,
-                        writer_opnode, opnode,
-                        ifield, target_topo)
+                writer_opnode = self.add_vertex(graph, writer_op)
+                self.add_edge(graph, writer_opnode, opnode, ifield, target_topo)
 
             # we only handle input field requirements when we are root graph
             # ie. target_dfield_requirements is None
@@ -1039,13 +873,10 @@ class GraphBuilder(object):
                     if (src_topo is not target_topo):
                         gprint('   >Redistributing field {} from up to date topologies {} to host topology {}.'.format(
                                 ifield.name, ' ,'.join(t.pretty_tag for t in src_topos), target_topo.pretty_tag))
-                    self.transpose(src_topo, target_axes,
-                            graph, vertex_properties, edge_properties)
-                    self.redistribute(target_topo, graph,
-                            vertex_properties, edge_properties, src_topo=src_topo)
+                    self.transpose(src_topo, target_axes, graph)
+                    self.redistribute(target_topo, graph, src_topo=src_topo)
                     # we can always reorder target because this a host topology
-                    self.reorder(target_topo, target_memory_order,
-                            graph, vertex_properties, edge_properties)
+                    self.reorder(target_topo, target_memory_order, graph)
                 elif (target_topo.backend.kind is Backend.OPENCL) and write_nodes:
                     # give source topo priority according to topology_affinity
                     src_topos = write_nodes.keys()
@@ -1054,18 +885,13 @@ class GraphBuilder(object):
                     if (src_topo is not target_topo):
                         gprint('   >Redistributing field {} from up to date topologies {} to device topology {}.'.format(
                                 ifield.name, ' ,'.join(t.pretty_tag for t in src_topos), target_topo.pretty_tag))
-                    self.reorder(src_topo, target_memory_order,
-                            graph, vertex_properties, edge_properties)
-                    self.redistribute(target_topo, graph,
-                            vertex_properties, edge_properties, src_topo=src_topo)
+                    self.reorder(src_topo, target_memory_order, graph)
+                    self.redistribute(target_topo, graph, src_topo=src_topo)
                     # target is always opencl so we transpose here
-                    self.transpose(target_topo, target_axes,
-                            graph, vertex_properties, edge_properties)
+                    self.transpose(target_topo, target_axes, graph)
                 else:
-                    self.transpose(target_topo, target_axes,
-                            graph, vertex_properties, edge_properties)
-                    self.reorder(target_topo, target_memory_order,
-                            graph, vertex_properties, edge_properties)
+                    self.transpose(target_topo, target_axes, graph)
+                    self.reorder(target_topo, target_memory_order, graph)
 
                 istate = dtopology_states[target_topo]
                 gprint2('       >Input state is now {}'.format(istate))
@@ -1077,21 +903,16 @@ class GraphBuilder(object):
                 output_states = {}
                 self.op_input_topology_states[writer_op]  = input_states
                 self.op_output_topology_states[writer_op] = output_states
-                vertex_properties['op_info'][writer_opnode] = _op_info(writer_op,
-                        input_states, output_states)
+                writer_opnode.set_op_info(writer_op, input_states, output_states)
 
             # add read dependency to last written node before current op
             # (so that inputs are modified before actual call to the operator)
             if (target_topo in write_nodes):
                 last_write_node = write_nodes[target_topo]
-                self.add_edge(graph, edge_properties,
-                        last_write_node, opnode,
-                        ifield, target_topo)
+                self.add_edge(graph, last_write_node, opnode, ifield, target_topo)
             elif (not is_root) and write_nodes:
                 for node in self.write_nodes.values():
-                    self.add_edge(graph, edge_properties,
-                            node, opnode,
-                            ifield, target_topo)
+                    self.add_edge(graph, node, opnode, ifield, target_topo)
 
             read_nodes.setdefault(target_topo, []).append(opnode)
             if is_new:
@@ -1100,9 +921,8 @@ class GraphBuilder(object):
             return istate
 
 
-        def handle_output(self, opnode, output_topo, oreqs,
-                operator, input_topology_states, invalidate_field,
-                graph, edge_properties, vertex_properties):
+        def handle_output(self, opnode, output_topo, oreqs, operator,
+                input_topology_states, invalidate_field, graph):
 
             ofield = self.field
             write_nodes   = self.write_nodes
@@ -1114,9 +934,8 @@ class GraphBuilder(object):
             # add dependency to last node written to prevent
             # concurent write-writes.
             if (output_topo in write_nodes):
-                self.add_edge(graph, edge_properties,
-                        write_nodes[output_topo], opnode,
-                        ofield, output_topo)
+                self.add_edge(graph, write_nodes[output_topo], 
+                        opnode, ofield, output_topo)
             
             if invalidate_field:
                 gprint('   >Invalidating output field {} on all topologies but {} because is has been freshly written.'.format(ofield.name, output_topo.pretty_tag))
@@ -1124,9 +943,7 @@ class GraphBuilder(object):
                 # to prevent concurent read-writes.
                 if output_topo in read_nodes:
                     for ro_node in read_nodes[output_topo]:
-                        self.add_edge(graph, edge_properties,
-                                ro_node, opnode,
-                                ofield, output_topo)
+                        self.add_edge(graph, ro_node, opnode, ofield, output_topo)
 
                 # remove read/write dependencies and states
                 write_nodes.clear()
@@ -1155,9 +972,6 @@ class GraphBuilder(object):
 
             return ostate
 
-        def output_as_input(self, target_topo, dstate,
-                graph, edge_properties, vertex_properties):
-
-            self.handle_input(None, target_topo, dstate,
-                    graph, edge_properties, vertex_properties, False)
+        def output_as_input(self, target_topo, dstate, graph):
+            self.handle_input(None, target_topo, dstate, graph,False)
 
diff --git a/hysop/operator/tests/test_absorption.py b/hysop/operator/tests/test_absorption.py
index ce2735ecf..e0bf8d80a 100644
--- a/hysop/operator/tests/test_absorption.py
+++ b/hysop/operator/tests/test_absorption.py
@@ -180,7 +180,7 @@ class TestVorticityAbsorption(object):
             dist = npw.abs(fout-fref)
             dinf = npw.max(dist)
             deps = int(npw.ceil(dinf/eps))
-            if (deps < 100):
+            if (deps < 200):
                 print '{}eps, '.format(deps),
                 continue
             has_nan = npw.any(npw.isnan(fout))
diff --git a/hysop/operator/tests/test_spectral_derivative.py b/hysop/operator/tests/test_spectral_derivative.py
index 5b3d93075..fbed428d1 100644
--- a/hysop/operator/tests/test_spectral_derivative.py
+++ b/hysop/operator/tests/test_spectral_derivative.py
@@ -275,7 +275,7 @@ class TestSpectralDerivative(object):
                     except OverflowError:
                         import numpy as np
                         deps = np.inf
-                    if (deps <= 10**(nidx+2)):
+                    if (deps <= 2*10**(nidx+2)):
                         if (j == 1):
                             print '{}eps ({})'.format(deps, dinf),
                         else:
diff --git a/hysop/problem.py b/hysop/problem.py
index cbd34801c..84e5eaf5c 100644
--- a/hysop/problem.py
+++ b/hysop/problem.py
@@ -81,13 +81,8 @@ class Problem(ComputationalGraph):
             self.check_unique_clenv()
 
     def check_unique_clenv(self):
-        reduced_graph = self.reduced_graph
-        operators = reduced_graph.vertex_properties['operators']
-
-        cl_env, op = None, None
-        for vid in self.sorted_nodes:
-            vertex = reduced_graph.vertex(vid)
-            op     = operators[vertex]
+        cl_env, first_op = None, None
+        for op in self.nodes:
             for topo in set(op.input_fields.values() + op.output_fields.values()):
                 if (topo.backend.kind == Backend.OPENCL):
                     if (cl_env is None):
@@ -105,13 +100,8 @@ class Problem(ComputationalGraph):
 
     def initialize_field(self, field, **kwds):
         """Initialize a field on all its input and output topologies."""
-        reduced_graph = self.reduced_graph
-        operators = reduced_graph.vertex_properties['operators']
-
         initialized = set()
-        for vid in self.sorted_nodes:
-            vertex = reduced_graph.vertex(vid)
-            op     = operators[vertex]
+        for op in self.nodes:
             # give priority to tensor field initialization
             for op_fields in (self.input_discrete_tensor_fields, self.output_discrete_tensor_fields,
                               op.input_discrete_tensor_fields, op.output_discrete_tensor_fields,
-- 
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