new_contents: import numpy as np
  import theano
  import theano.tensor as T
  fX = theano.config.floatX
  s = theano.shared(np.zeros((30000, 10000), dtype=fX))
  fn1 = theano.function([], updates=[(s, s + 1)])
  fn2 = theano.function([], updates=[(s, T.inc_subtensor(s[1497], s[1497] ** 2))])
  
  """
  on cpu:
  %timeit fn1()  # 166ms
  %timeit fn2()  # 14.4us
  """
  
subject: add benchmark for sparse updates