added basic transaction management

git-svn-id: svn://svn.cy55.de/Zope3/src/cybertools/trunk@1260 fd906abe-77d9-0310-91a1-e0d9ade77398

brain/README.txt

@@ -18,17 +18,29 @@ when creating a synapsis:
   []
   >>> n01.receivers == [s0102]
   True
-  >>> n01.state.value
-  1.0
-  >>> n02.state.value
-  1.0
+  >>> n01.getState()
+  <State 0.0>
+  >>> n02.getState()
+  <State 0.0>
 
-When we trigger a neuron, all its receivers get triggered so that the
-receivers' state is updated:
+When we change the state of a neuron and notify it, all its receiver synapses
+get triggered so that the receiver neurons' states are updated:
 
-  >>> n01.trigger()
-  >>> n01.state.value
-  1.0
-  >>> n02.state.value
-  2.0
+  >>> from cybertools.brain.state import State
+  >>> n01.setState(State(1.0))
+  >>> n01.getState()
+  <State 1.0>
+  >>> n01.notify()
+  >>> n02.getState()
+  <State 1.0>
 
+To allow for concurrent (thread-safe) access to the brain all changes to
+the neurons' states is under the control of a transaction. If we end the
+current transaction all state changes will be forgotton:
+
+  >>> from cybertools.brain.transaction import endTransaction
+  >>> endTransaction()
+  >>> n01.getState()
+  <State 0.0>
+  >>> n02.getState()
+  <State 0.0>

brain/interfaces.py

@@ -34,24 +34,32 @@ class ISynapsis(Interface):
 
     transition = Attribute("A transition changes the sender neuron's state.")
 
+    def trigger(transaction=None):
+        """ Recalculate the receiver neuron's state by executing the
+            synapse's transition using the state of the sender neuron.
+        """
+
 
 class INeuron(Interface):
 
-    state = Attribute("The current state of the neuron")
-
     senders = Attribute("The sender synapses")
     receivers = Attribute("The receiver synapses")
 
-    def trigger():
+    def setState(state, transaction=None):
+        """ Set the neuron's state.
+        """
+
+    def getState(transaction=None):
+        """ Return the neuron's state.
+        """
+
+    def notify(transaction=None):
         """ Notifies the neuron that something has happened. This method
-            executes all transitions from all sender synapses in order to
-            calculate the neuron's new state;
-            then it should call the trigger() method on all downstream
-            (receiver)neurons.
+            calls the trigger() method on all downstream (receiver) synapses.
             In addition it may perform side effects like changing
             transition properties of adjacent synapses or even create new
             synapses or neurons; this side effects should happen before
-            triggering the receiver neurons.
+            triggering the receiver synapses.
         """
 
 
@@ -62,7 +70,12 @@ class IState(Interface):
 
 class ITransition(Interface):
 
-    def execute(state):
-        """ Transform state to a new state value and return it.
+    def execute(transaction=None):
+        """ Transform the receiver's state to a new state value and return it.
         """
 
+
+class ITransaction(Interface):
+    """ A transaction that keeps track of the neurons' states.
+    """
+

brain/neuron.py

@@ -19,12 +19,13 @@
 """
 A simple basic implementation of Neuron and Synapsis.
 
-$Id: type.py 1129 2006-03-19 09:46:08Z helmutm $
+$Id$
 """
 
 from zope.interface import implements
 from cybertools.brain.interfaces import INeuron, ISynapsis
 from cybertools.brain.state import State, Transition
+from cybertools.brain.transaction import getTransaction
 
 
 class Synapsis(object):
@@ -33,10 +34,6 @@ class Synapsis(object):
 
     implements(ISynapsis)
 
-    sender = None
-    reciever = None
-    transition = None
-
     def __init__(self, sender, receiver):
         self.sender = sender
         sender.receivers.append(self)
@@ -44,28 +41,33 @@ class Synapsis(object):
         receiver.senders.append(self)
         self.transition = Transition(self)
 
+    def trigger(self, transaction=None):
+        receiver = self.receiver
+        receiver.setState(self.transition.execute(transaction), transaction)
+        receiver.notify(transaction)
+
 
 class Neuron(object):
 
     implements(INeuron)
 
-    state = None
-
     def __init__(self):
         self.senders = []
         self.receivers = []
         self.state = State()
-        self.active = False
 
-    def trigger(self):
-        if self.active:  # avoid cycles
-            return
-        self.active = True
-        state = self.state
-        for s in self.senders:
-            state = s.transition.execute(state)
-        self.state = state
+    def setState(self, state, transaction=None):
+        transaction = getTransaction(transaction)
+        transaction.setState(self, state)
+
+    def getState(self, transaction=None):
+        if transaction is None:
+            transaction = getTransaction(create=False)
+            if transaction is None:
+                return self.state
+        return transaction.getState(self)
+
+    def notify(self, transaction=None):
         for r in self.receivers:
-            r.receiver.trigger()
-        self.active = False
+            r.trigger(transaction)
 

brain/state.py

@@ -32,9 +32,12 @@ class State(object):
 
     implements(IState)
 
-    def __init__(self, value=1.0):
+    def __init__(self, value=0.0):
         self.value = value
 
+    def __repr__(self):
+        return '<State %0.1f>' % self.value
+
 
 class Transition(object):
 
@@ -44,7 +47,9 @@ class Transition(object):
         self.synapsis = synapsis
         self.factor = factor
 
-    def execute(self, state):
-        return State(state.value + self.synapsis.sender.state.value * self.factor)
+    def execute(self, transaction=None):
+        oldState = self.synapsis.receiver.getState(transaction)
+        senderState = self.synapsis.sender.getState(transaction)
+        return State(oldState.value + senderState.value * self.factor)
 
 

brain/transaction.py

@@ -0,0 +1,63 @@
+#
+#  Copyright (c) 2006 Helmut Merz helmutm@cy55.de
+#
+#  This program is free software; you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software
+#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+
+"""
+Transaction management.
+
+$Id$
+"""
+
+from zope.interface import implements
+from cybertools.brain.interfaces import ITransaction
+
+
+class Transaction(object):
+
+    implements(ITransaction)
+
+    def __init__(self):
+        self.states = {}
+
+    def setState(self, neuron, state):
+        self.states[neuron] = state
+
+    def getState(self, neuron):
+        return self.states.get(neuron, neuron.state)
+
+
+transactions = []
+
+def getTransaction(transaction=None, create=True):
+    if transaction is None:
+        if transactions:
+            transaction = transactions[0]
+        elif create:
+            transaction = Transaction()
+            transactions.append(transaction)
+        else:
+            return None
+    return transaction
+
+def endTransaction(transaction=None):
+    if transaction is None:
+        if transactions:
+            del transactions[0]
+    else:
+        if transaction in transactions:
+            del transactions[transactions.index(transaction)]
+