scan2.py

# https://deeplearningcourses.com/c/unsupervised-machine-learning-hidden-markov-models-in-python
# https://udemy.com/unsupervised-machine-learning-hidden-markov-models-in-python
# http://lazyprogrammer.me
# theano scan example: calculate fibonacci
from __future__ import print_function, division
from builtins import range
# Note: you may need to update your version of future
# sudo pip install -U future


import numpy as np
import theano
import theano.tensor as T


N = T.iscalar('N')

def recurrence(n, fn_1, fn_2):
  return fn_1 + fn_2, fn_1

outputs, updates = theano.scan(
  fn=recurrence,
  sequences=T.arange(N),
  n_steps=N,
  outputs_info=[1., 1.]
)

fibonacci = theano.function(
  inputs=[N],
  outputs=outputs,
)

o_val = fibonacci(8)

print("output:", o_val)