Fix opt crash and better error msg.

theano/sandbox/gpuarray/opt.py

@@ -763,7 +763,7 @@ def local_gpua_gemm(node, context_name):
 @op_lifter([tensor.blas.BatchedDot])
 def local_gpua_gemmbatch(node, context_name):
     a, b = node.inputs
-    c = tensor.AllocEmpty((a.shape[0], a.shape[1], b.shape[2]))
+    c = tensor.AllocEmpty(a.dtype)(a.shape[0], a.shape[1], b.shape[2])
     return gpugemmbatch_no_inplace(c, 1.0, a, b, 0.0)
 
 

theano/tensor/basic.py

@@ -6218,7 +6218,7 @@ class AllocEmpty(gof.Op):
 
     # specify the type of the data
     def __init__(self, dtype):
-        assert isinstance(dtype, str)
+        assert isinstance(dtype, str), dtype
         self.dtype = dtype.lower()
 
     def validate_shape(self, shape):