Fix for speeding up scan

Before, scan used to add another layer of abstraction between constants and the inner function, so even if you would give as a non sequence a constant the inner function will treat it like a normal theano variable stopping certain optimizations to happen.

Fix for speeding up scan
f09f515b · Razvan Pascanu · 9f78a32b · f09f515b
--- a/theano/scan_module/scan.py
+++ b/theano/scan_module/scan.py
@@ -814,6 +814,8 @@ def scan( fn

    ## Step 5.6 all shared variables with no update rules
    def new_variable( v ):
+        if isinstance(new_variable, tensor.Constant):
+            return v.clone()
        new_v = safe_new(v)
        if getattr(v,'name', None) is not None:
            new_v.name = v.name + '_copy'