In the key of the Theano cache, use the md5 hash of the constant value.

theano/gof/cc.py

@@ -906,6 +906,8 @@ class CLinker(link.Linker):
             if isinstance(i, graph.Constant): #orphans
                 if id(i) not in constant_ids:
                     isig = (i.signature(), topological_pos, i_idx)
+                    if hasattr(isig[0], "theano_hash"):
+                        isig = (isig[0].theano_hash(), topological_pos, i_idx)
                     try:
                         hash(isig)
                     except Exception: #generic constants don't have a hashable signature

theano/sparse/basic.py

@@ -16,6 +16,7 @@ import scipy.sparse
 from theano import gof, tensor, compile, scalar, config
 from theano.gof.python25 import all
 from theano.tensor import blas
+from theano.sparse.utils import hash_from_sparse
 
 sparse_formats = ['csc', 'csr']
 
@@ -278,6 +279,10 @@ class SparseConstantSignature(tuple):
         (a, b) = self
         return hash(type(self)) ^ hash(a) ^ hash(type(b))
 
+    def theano_hash(self):
+        (_, d) = self
+        return hash_from_sparse(d)
+
 
 class SparseConstant(gof.Constant, _sparse_py_operators):
     dtype = property(lambda self: self.type.dtype)

theano/tensor/basic.py

@@ -20,6 +20,7 @@ from theano import scalar as scal
 from theano.gof.python25 import partial, any, all
 from theano import compile, printing
 from theano.printing import pprint, min_informative_str
+from theano.tensor.utils import hash_from_ndarray
 
 # We use these exceptions as well.
 from theano.scalar import ComplexError, IntegerDivisionError
@@ -1505,6 +1506,10 @@ class TensorConstantSignature(tuple):
         t, d = self
         return hashtype(self) ^ hash(t) ^ hash(d.shape) ^ hash(self.sum)
 
+    def theano_hash(self):
+        _, d = self
+        return hash_from_ndarray(d)
+
     def _get_sum(self):
         """Compute sum of non NaN / Inf values in the array."""
         try: