clone_scan.py

import numpy

import theano
from theano import tensor
from theano.printing import debugprint

floatX = theano.config.floatX
foo_a, foo_x, r = 3 * [None]

def foo(x, a):
    global foo_a, foo_x, r
    foo_a = a
    foo_x = x
    r = a + x
    return r

x = tensor.vector('x')
s, _ = theano.scan(foo, sequences=x,
                   outputs_info=[numpy.array(0, dtype=floatX)])
r2 = foo_x - foo_a
# Prints two similar scan inner graphs
debugprint(s)
debugprint(theano.clone(s, replace=[(r, r2)]))