Merge pull request #2056 from nouiz/Tanjay94-TV

doc/library/config.txt

@@ -184,6 +184,15 @@ import theano and print the config variable, as in:
     and similar functions.  It also sets the default theano bit width for
     arguments passed as Python floating-point numbers.
 
+.. attribute:: warn_float64
+
+    String value: either 'ignore', 'warn', 'raise' or 'pdb'
+
+    Default: 'float64'
+
+    When creating a TensorVariable with dtype float64, what should be done?
+    This is useful to help find upcast to float64 in user code.
+
 .. attribute:: allow_gc
 
     Bool value: either ``True`` or ``False``

theano/configdefaults.py

@@ -24,6 +24,14 @@ AddConfigVar('floatX',
              EnumStr('float64', 'float32', convert=floatX_convert,),
 )
 
+AddConfigVar('warn_float64',
+             "Do an action when a tensor variable with float64 dtype is"
+             " created. They can't be run on the GPU with the current(old)"
+             " gpu back-end and are slow with gamer GPUs.",
+             EnumStr('ignore', 'warn', 'raise', 'pdb'),
+             in_c_key=False,
+)
+
 AddConfigVar('cast_policy',
         "Rules for implicit type casting",
         EnumStr('custom', 'numpy+floatX',

theano/tensor/var.py

 import copy
+import pdb
+import sys
+import traceback as tb
+import warnings
 
 import numpy
 
@@ -9,6 +13,7 @@ from theano.gof import Constant, Variable
 from theano.gof.utils import hashtype
 from theano.tensor.utils import hash_from_ndarray
 from theano.tensor.type import TensorType
+from theano.configparser import config
 
 
 class AsTensorError(TypeError):
@@ -574,6 +579,34 @@ class _tensor_py_operators:
 class TensorVariable(_tensor_py_operators, Variable):
     """Subclass to add the tensor operators to the basic `Variable` class."""
 
+    def __init__(self, type, owner=None, index=None, name=None):
+        super(TensorVariable, self).__init__(type, owner=owner,
+                                             index=index, name=name)
+        if (config.warn_float64 != 'ignore' and type.dtype == 'float64'):
+            msg = ('You are creating a TensorVariable '
+                   'with float64 dtype. You requested an action via '
+                   'the Theano flag warn_float64={ignore,warn,raise,pdb}.')
+            if config.warn_float64 == "warn":
+                # Get the user stack. We don't want function inside the
+                # tensor and gof directory to be shown to the user.
+                x = tb.extract_stack()
+                nb_rm = 0
+                while x:
+                    file_path = x[-1][0]
+                    rm = False
+                    for p in ["theano/tensor/",
+                              "theano/gof/"]:
+                        if p in file_path:
+                            x = x[:-1]
+                            nb_rm += 1
+                            rm = True
+                    if not rm:
+                        break
+                warnings.warn(msg, stacklevel=1 + nb_rm)
+            elif config.warn_float64 == "raise":
+                raise Exception(msg)
+            elif config.warn_float64 == 'pdb':
+                import pdb;pdb.set_trace()
 TensorType.Variable = TensorVariable