# HG changeset patch
# User bergstrj@iro.umontreal.ca
# Date 1206591556 14400
# Node ID 60b164a0d84ae46b88ad59f42c6d2e99f2489c1f
# Parent  759d17112b2389d669cc70bbcf101f5bee131aa1# Parent  5ede27026e05aba55213589b00795f7091b4ee07
merged

diff -r 759d17112b23 -r 60b164a0d84a gradient_learner.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gradient_learner.py	Thu Mar 27 00:19:16 2008 -0400
@@ -0,0 +1,50 @@
+
+from learner import *
+from tensor import *
+import gradient
+from compile import Function
+from gradient_based_optimizer import *
+
+class GradientLearner(Learner):
+    """
+    Base class for gradient-based optimization of a training criterion
+    that can consist in two parts, an additive part over examples, and
+    an example-independent part (usually called the regularizer).
+    The user provides a Theano formula that maps the fields of a training example
+    and parameters to output fields (for the use function), one of which must be a cost
+    that is the training criterion to be minimized. Subclasses implement
+    a training strategy that uses the function to compute gradients and
+    to compute outputs in the update method.
+    The inputs, parameters, and outputs are lists of Theano tensors,
+    while the example_wise_cost and regularization_term are Theano tensors.
+    The user can specify a regularization coefficient that multiplies the regularization term.
+    The training algorithm looks for parameters that minimize
+       regularization_coefficienet * regularization_term(parameters) +
+       sum_{inputs in training_set} example_wise_cost(inputs,parameters)
+    i.e. the regularization_term should not depend on the inputs, only on the parameters.
+    The learned function can map a subset of inputs to a subset of outputs (as long as the inputs subset
+    includes all the inputs required in the Theano expression for the selected outputs).
+    It is assumed that all the inputs are provided in the training set, but
+    not necessarily when using the learned function.
+    """
+    def __init__(self, inputs, parameters, outputs, example_wise_cost, regularization_term,
+                 gradient_based_optimizer=StochasticGradientDescent(), regularization_coefficient = astensor(1.0)):
+        self.inputs = inputs
+        self.outputs = outputs
+        self.parameters = parameters
+        self.example_wise_cost = example_wise_cost
+        self.regularization_term = regularization_term
+        self.gradient_based_optimizer = gradient_based_optimizer
+        self.regularization_coefficient = regularization_coefficient
+        self.parameters_example_wise_gradient = gradient.grad(example_wise_cost, parameters)
+        self.parameters_regularization_gradient = gradient.grad(self.regularization_coefficient * regularization, parameters)
+        if example_wise_cost not in outputs:
+            outputs.append(example_wise_cost)
+        if regularization_term not in outputs:
+            outputs.append(regularization_term)
+        self.example_wise_gradient_fn = Function(inputs + parameters, 
+                                       [self.parameters_example_wise_gradient + self.parameters_regularization_gradient])
+        self.use_functions = {frozenset([input.name for input in inputs]) : Function(inputs, outputs)}
+
+    def update(self,training_set):
+
diff -r 759d17112b23 -r 60b164a0d84a learner.py
--- a/learner.py	Wed Mar 26 21:05:14 2008 -0400
+++ b/learner.py	Thu Mar 27 00:19:16 2008 -0400
@@ -1,6 +1,5 @@
 
 from dataset import *
-from statscollector import *
     
 class Learner(object):
     """Base class for learning algorithms, provides an interface
@@ -24,15 +23,17 @@
         """
         raise NotImplementedError
 
-    def update(self,training_set):
+    def update(self,training_set,train_stats_collector=None):
         """
         Continue training a learner, with the evidence provided by the given training set.
         Hence update can be called multiple times. This is particularly useful in the
         on-line setting or the sequential (Bayesian or not) settings.
         The result is a function that can be applied on data, with the same
         semantics of the Learner.use method.
+        The user may optionally provide a training StatsCollector that is used to record
+        some statistics of the outputs computed during training.
         """
-        return self.use
+        return self.use # default behavior is 'non-adaptive', i.e. update does not do anything
     
     
     def __call__(self,training_set):