improved error messages for invalid values

doc/extending/fibby.txt

@@ -45,6 +45,7 @@ you should check the strides and alignment.
       return theano.Apply(self, 
         inputs=[x_],
         outputs=[x_.type()])
+      # using x_.type() is dangerous, it copies x's broadcasting behaviour
 
     def perform(self, node, inputs, output_storage):
       x, = inputs

doc/extending/unittest.txt

@@ -401,7 +401,8 @@ Here is the prototype for the verify_grad function.
 >>> def verify_grad(fun, pt, n_tests=2, rng=None, eps=1.0e-7, abs_tol=0.0001, rel_tol=0.0001):
 
 ``verify_grad`` raises an Exception if the difference between the analytic gradient and
-numerical gradient (computed through the Finite Difference Method) exceeds
+numerical gradient (computed through the Finite Difference Method) of a random
+projection of the fun's output to a scalar  exceeds
 both the given absolute and relative tolerances.
 
 The parameters are as follows:
@@ -417,7 +418,7 @@ The parameters are as follows:
 * ``n_tests``: number of times to run the test
 
 * ``rng``: random number generator used to generate a random vector u,
-  we check the gradient of dot(u,fn) at pt
+  we check the gradient of sum(u*fn) at pt
 
 * ``eps``: stepsize used in the Finite Difference Method
 

theano/compile/debugmode.py

@@ -330,13 +330,14 @@ class StochasticOrder(DebugModeError):
 
 class InvalidValueError(DebugModeError):
     """Exception: some Op an output value that is inconsistent with the Type of that output"""
-    def __init__(self, r, v, client_node=None, hint='none'):
+    def __init__(self, r, v, client_node=None, hint='none', specific_hint='none'):
         #super(InvalidValueError, self).__init__()
         DebugModeError.__init__(self)#to be compatible with python2.4
         self.r = r
         self.v = v
         self.client_node = client_node
         self.hint=hint
+        self.specific_hint=specific_hint
 
     def __str__(self):
         r, v = self.r, self.v
@@ -358,6 +359,7 @@ class InvalidValueError(DebugModeError):
             pass
         client_node = self.client_node
         hint = self.hint
+        specific_hint = self.specific_hint
         return """InvalidValueError
         type(variable) = %(type_r)s
         variable       = %(r)s
@@ -370,6 +372,7 @@ class InvalidValueError(DebugModeError):
         isfinite       = %(v_isfinite)s
         client_node    = %(client_node)s
         hint           = %(hint)s
+        specific_hint   = %(specific_hint)s
         """ % locals()
 
 ########################
@@ -1070,7 +1073,7 @@ class _Linker(gof.link.LocalLinker):
                         # check output values for type-correctness
                         for r in node.outputs:
                             if not r.type.is_valid_value(storage_map[r][0]):
-                                raise InvalidValueError(r, storage_map[r][0], hint='perform output')
+                                raise InvalidValueError(r, storage_map[r][0], hint='perform output', specific_hint = r.type.value_validity_msg(storage_map[r][0]))
                             #if r in r_vals:
 
                         _check_inputs(node, storage_map, r_vals, dr_vals, active_order_set,

theano/gof/type.py

@@ -227,6 +227,10 @@ class PureType(object):
         except (TypeError, ValueError):
             return False
     
+    def value_validity_msg(self, a):
+        """Optional: return a message explaining the output of is_valid_value"""
+        return "none"
+
     def make_variable(self, name = None):
         """Return a new `Variable` instance of Type `self`.
 

theano/tensor/basic.py

@@ -19,7 +19,6 @@ from theano import gradient
 import elemwise
 from theano import scalar as scal
 from theano.gof.python25 import partial, any, all
-
 from theano import compile, printing
 from theano.printing import pprint, Print
 
@@ -430,6 +429,14 @@ class TensorType(Type):
             raise ValueError("non-finite elements not allowed")
         return data
 
+    def value_validity_msg(self, a):
+        try:
+            self.filter(a, True)
+        except Exception, e:
+            return str(e)
+        return "value is valid"
+        
+
     def dtype_specs(self):
         """Return a tuple (python type, c type, numpy typenum) that corresponds to
         self.dtype.
@@ -4046,7 +4053,8 @@ def verify_grad(fun, pt, n_tests=2, rng=None, eps=None, abs_tol=None, rel_tol=No
                     rng=numpy.random)
 
     Raises an Exception if the difference between the analytic gradient and
-    numerical gradient (computed through the Finite Difference Method) exceeds
+    numerical gradient (computed through the Finite Difference Method) of a random
+    projection of the fun's output to a scalar exceeds
     the given tolerance.
 
     :param fun: a Python function that takes Theano variables as inputs,
@@ -4055,7 +4063,7 @@ def verify_grad(fun, pt, n_tests=2, rng=None, eps=None, abs_tol=None, rel_tol=No
     :param pt: the list of numpy.ndarrays to use as input values.
         These arrays must be either float32 or float64 arrays.
     :param n_tests: number of times to run the test
-    :param rng: random number generator used to sample u, we test gradient of dot(u,fun) at pt
+    :param rng: random number generator used to sample u, we test gradient of sum(u * fun) at pt
     :param eps: stepsize used in the Finite Difference Method (Default None is type-dependent)
     :param abs_tol: absolute tolerance used as threshold for gradient comparison
     :param rel_tol: relative tolerance used as threshold for gradient comparison