def test_lookahead_edge_cases(self, sync_period, slow_step_size,
correct_result):
"""Checks special cases of the lookahed optimizer parameters."""
# These edge cases are important to check since users might use them as
# simple ways of disabling lookahead in experiments.
optimizer = lookahead.lookahead(_test_optimizer(-1), sync_period,
slow_step_size)
final_params, _ = self.loop(optimizer,
num_steps=2,
params=self.synced_initial_params)
chex.assert_tree_all_close(final_params.slow, correct_result)
def test_lookahead(self):
"""Tests the lookahead optimizer in an analytically tractable setting."""
sync_period = 3
optimizer = lookahead.lookahead(_test_optimizer(-0.5),
sync_period=sync_period,
slow_step_size=1 / 3)
final_params, _ = self.loop(optimizer, 2 * sync_period,
self.synced_initial_params)
# x steps must be: 3 -> 2 -> 1 -> 2 (sync) -> 1 -> 0 -> 1 (sync).
# Similarly for y (with sign flipped).
correct_final_params = {'x': 1, 'y': -1}
chex.assert_tree_all_close(final_params.slow, correct_final_params)
def test_lookahead_state_reset(self, reset_state):
"""Checks that lookahead resets the fast optimizer state correctly."""
num_steps = sync_period = 3
fast_optimizer = _test_optimizer(-0.5)
optimizer = lookahead.lookahead(fast_optimizer,
sync_period=sync_period,
slow_step_size=0.5,
reset_state=reset_state)
_, opt_state = self.loop(optimizer, num_steps,
self.synced_initial_params)
fast_state = opt_state.fast_state
if reset_state:
correct_state = fast_optimizer.init(self.initial_params)
else:
_, correct_state = self.loop(fast_optimizer, num_steps,
self.initial_params)
chex.assert_tree_all_close(fast_state, correct_state)