def filter(self, items: Iterable[Any]) -> Sequence[Any]:
rng = CobaRandom(self._seed)
if self._max_count == 0:
return []
if self._max_count == None:
return Take(self._count).filter(rng.shuffle(list(items)))
W = 1
items = iter(items)
reservoir = rng.shuffle(list(islice(items, self._max_count)))
try:
while True:
[r1, r2, r3] = rng.randoms(3)
W = W * math.exp(math.log(r1) / (self._max_count or 1))
S = math.floor(math.log(r2) / math.log(1 - W))
reservoir[int(r3 * self._max_count - .001)] = next(
islice(items, S, S + 1))
except StopIteration:
pass
return Take(self._count).filter(reservoir)
def test_regression_learning(self):
vw = VowpalMediator().init_learner("--quiet", 1)
n_features = 10
n_examples = 1000
rng = CobaRandom(1)
weights = rng.randoms(n_features)
rows = [rng.randoms(n_features) for _ in range(n_examples)]
labels = [sum([w * r for w, r in zip(weights, row)]) for row in rows]
examples = list(zip(rows, labels))
self.assertEqual(0, vw.predict(vw.make_example({'x': rows[0]}, None)))
pred_errs = []
for row, label in examples[int(.9 * n_examples):]:
pred_errs.append(
vw.predict(vw.make_example({"x": row}, None)) - label)
pre_learn_mse = sum([e**2 for e in pred_errs]) // len(pred_errs)
for row, label in examples[0:int(.9 * n_examples)]:
vw.learn(vw.make_example({"x": row}, str(label)))
pred_errs = []
for row, label in examples[int(.9 * n_examples):]:
pred_errs.append(
vw.predict(vw.make_example({"x": row}, None)) - label)
post_learn_mse = sum([e**2 for e in pred_errs]) / len(pred_errs)
self.assertNotAlmostEqual(0, pre_learn_mse, places=2)
self.assertAlmostEqual(0, post_learn_mse, places=2)
def __init__(self,
n_interactions: int,
n_actions: int = 10,
n_context_features: int = 10,
n_action_features: int = 10,
n_exemplars: int = 10,
kernel: Literal['linear', 'polynomial',
'exponential'] = 'exponential',
degree: int = 2,
gamma: float = 1,
seed: int = 1) -> None:
"""Instantiate a KernelSyntheticSimulation.
Args:
n_interactions: The number of interactions the simulation should have.
n_actions: The number of actions each interaction should have.
n_context_features: The number of features each context should have.
n_action_features: The number of features each action should have.
n_exemplars: The number of exemplar action, context pairs.
kernel: The family of the kernel basis functions.
degree: This argument is only relevant when using polynomial kernels.
gamma: This argument is only relevant when using exponential kernels.
seed: The random number seed used to generate all features, weights and noise in the simulation.
"""
self._args = (n_interactions, n_actions, n_context_features,
n_action_features, n_exemplars, kernel, degree, gamma,
seed)
self._n_actions = n_actions
self._n_context_features = n_context_features
self._n_action_features = n_action_features
self._n_exemplars = n_exemplars
self._seed = seed
self._kernel = kernel
self._degree = degree
self._gamma = gamma
rng = CobaRandom(seed)
#if there are no features then we are unable to define exemplars
if n_action_features + n_context_features == 0: n_exemplars = 0
feat_gen = lambda n: tuple(rng.gausses(n, 0, .75))
one_hot_acts = OneHotEncoder().fit_encodes(range(n_actions))
self._exemplars = [[
feat_gen(n_action_features + n_context_features)
for _ in range(n_exemplars)
] for _ in range(1 if n_action_features else n_actions)]
weight_count = n_actions if n_exemplars == 0 else n_exemplars
self._weights = [1 - 2 * w for w in rng.randoms(weight_count)]
self._bias = 0
if kernel == 'polynomial':
#this ensures the dot-product between F and an exemplar is in [0,upper_bound]
#This ensures that higher-order polynomials will remain reasonably well behaved
upper_bound = (1.5)**(1 / degree) - 1
self._exemplars = [[[upper_bound * ee / sum(e) for ee in e]
for e in E] for E in self._exemplars]
def context(index: int) -> Context:
return feat_gen(n_context_features) if n_context_features else None
def actions(index: int, context: Context) -> Sequence[Action]:
return [feat_gen(n_action_features) for _ in range(n_actions)
] if n_action_features else one_hot_acts
def reward(index: int, context: Context, action: Action) -> float:
if n_exemplars == 0:
return self._bias + self._weights[action.index(1)]
#handles None context
context = context or []
if n_action_features:
f = list(context) + list(action)
W = self._weights
E = self._exemplars[0]
else:
f = list(context)
W = self._weights
E = self._exemplars[action.index(1)]
if kernel == "linear":
K = lambda x1, x2: self._linear_kernel(x1, x2)
if kernel == "polynomial":
K = lambda x1, x2: self._polynomial_kernel(
x1, x2, self._degree)
if kernel == "exponential":
K = lambda x1, x2: self._exponential_kernel(
x1, x2, self._gamma)
return self._bias + sum([w * K(e, f) for w, e in zip(W, E)])
rewards = [
reward(i, c, a) for i in range(100) for c in [context(i)]
for a in actions(i, c)
]
m = mean(rewards)
s = (max(rewards) - min(rewards)) or 1
self._bias = 0.5 - m / s
self._weights = [w / s for w in self._weights]
super().__init__(n_interactions, context, actions, reward)
def __init__(self,
n_interactions: int,
n_actions: int = 10,
n_context_features: int = 10,
n_action_features: int = 10,
reward_features: Sequence[str] = ["a", "xa"],
seed: int = 1) -> None:
"""Instantiate a LinearSyntheticSimulation.
Args:
n_interactions: The number of interactions the simulation should have.
n_actions: The number of actions each interaction should have.
n_context_features: The number of features each context should have.
n_action_features: The number of features each action should have.
reward_features: The features in the simulation's linear reward function.
seed: The random number seed used to generate all features, weights and noise in the simulation.
"""
self._args = (n_interactions, n_actions, n_context_features,
n_action_features, reward_features, seed)
self._n_actions = n_actions
self._n_context_features = n_context_features
self._n_action_features = n_action_features
self._reward_features = reward_features
self._seed = seed
if not self._n_context_features:
reward_features = list(
set(filter(None,
[f.replace('x', '') for f in reward_features])))
if not self._n_action_features:
reward_features = list(
set(filter(None,
[f.replace('a', '') for f in reward_features])))
rng = CobaRandom(seed)
feat_encoder = InteractionsEncoder(reward_features)
#to try and make sure high-order polynomials are well behaved
#we center our context and action features on 1 and give them
#a very small amount of variance. Then, in post processing, we
#shift and re-scale our reward to center and fill in [0,1].
max_degree = max([len(f)
for f in reward_features]) if reward_features else 1
feat_gen = lambda n: tuple([
g * rng.choice([1, -1])
for g in rng.gausses(n, mu=1, sigma=1 / (2 * max_degree))
])
one_hot_acts = OneHotEncoder().fit_encodes(range(n_actions))
feature_count = len(
feat_encoder.encode(x=[1] * n_context_features,
a=[1] * n_action_features))
weight_parts = 1 if n_action_features else n_actions
weight_count = 1 if feature_count == 0 else feature_count
self._weights = [[1 - 2 * w for w in rng.randoms(weight_count)]
for _ in range(weight_parts)]
self._bias = 0
self._clip = False
def context(index: int) -> Context:
return feat_gen(n_context_features) if n_context_features else None
def actions(index: int, context: Context) -> Sequence[Action]:
return [feat_gen(n_action_features) for _ in range(n_actions)
] if n_action_features else one_hot_acts
def reward(index: int, context: Context, action: Action) -> float:
F = feat_encoder.encode(x=context, a=action) or [1]
W = self._weights[0 if n_action_features else action.index(1)]
return self._bias + sum([w * f for w, f in zip(W, F)])
rewards = [
reward(i, c, a) for i in range(100) for c in [context(i)]
for a in actions(i, c)
]
m = mean(rewards)
s = (max(rewards) - min(rewards)) or 1
self._bias = 0.5 - m / s
self._weights = [[w / s for w in W] for W in self._weights]
self._clip = True
super().__init__(n_interactions, context, actions, reward)
def __init__(self,
n_interactions: int = 500,
n_actions: int = 10,
n_features: int = 10,
context_features: bool = True,
action_features: bool = True,
sparse: bool = False,
seed: int = 1) -> None:
self._n_bandits = n_actions
self._n_features = n_features
self._context_features = context_features
self._action_features = action_features
self._seed = seed
r = CobaRandom(seed)
context: Callable[[int], Context]
actions: Callable[[int, Context], Sequence[Action]]
rewards: Callable[[int, Context, Action], float]
sparsify = lambda x: (tuple(range(len(x))), tuple(x)
) if sparse else tuple(x)
unsparse = lambda x: x[1] if sparse else x
normalize = lambda X: [x / sum(X) for x in X]
if not context_features and not action_features:
means = [
m / n_actions + 1 / (2 * n_actions)
for m in r.randoms(n_actions)
]
actions_features = []
for i in range(n_actions):
action = [0] * n_actions
action[i] = 1
actions_features.append(tuple(action))
context = lambda i: None
actions = lambda i, c: sparsify(actions_features)
rewards = lambda i, c, a: means[unsparse(a).index(1)] + (r.random(
) - .5) / n_actions
if context_features and not action_features:
#normalizing allows us to make sure our reward is in [0,1]
bandit_thetas = [r.randoms(n_features) for _ in range(n_actions)]
theta_totals = [sum(theta) for theta in bandit_thetas]
bandit_thetas = [[
t / norm for t in theta
] for theta, norm in zip(bandit_thetas, theta_totals)]
actions_features = []
for i in range(n_actions):
action = [0] * n_actions
action[i] = 1
actions_features.append(tuple(action))
context = lambda i: sparsify(r.randoms(n_features))
actions = lambda i, c: [sparsify(af) for af in actions_features]
rewards = lambda i, c, a: sum([
cc * t for cc, t in zip(unsparse(c), bandit_thetas[unsparse(a).
index(1)])
])
if not context_features and action_features:
theta = r.randoms(n_features)
context = lambda i: None
actions = lambda i, c: [
sparsify(normalize(r.randoms(n_features)))
for _ in range(r.randint(2, 10))
]
rewards = lambda i, c, a: float(
sum([cc * t for cc, t in zip(theta, unsparse(a))]))
if context_features and action_features:
context = lambda i: sparsify(r.randoms(n_features))
actions = lambda i, c: [
sparsify(normalize(r.randoms(n_features)))
for _ in range(r.randint(2, 10))
]
rewards = lambda i, c, a: sum(
[cc * t for cc, t in zip(unsparse(c), unsparse(a))])
super().__init__(n_interactions, context, actions, rewards)
def test_cb_adf_learning(self):
learner = VowpalArgsLearner()
n_actions = 3
n_features = 10
n_examples = 2000
rng = CobaRandom(11111)
contexts = [rng.randoms(n_features) for _ in range(n_examples)]
pre_learn_rewards = []
for context in contexts[:int(.9 * n_examples)]:
actions = [rng.randoms(n_features) for _ in range(n_actions)]
rewards = [
sum([a * c for a, c in zip(action, context)])
for action in actions
]
rewards = [int(r == max(rewards)) for r in rewards]
pre_learn_rewards.append(
rng.choice(rewards,
learner.predict(context, actions)[0]))
for context in contexts[:int(.9 * n_examples)]:
actions = [rng.randoms(n_features) for _ in range(n_actions)]
rewards = [
sum([a * c for a, c in zip(action, context)])
for action in actions
]
rewards = [int(r == max(rewards)) for r in rewards]
probs, info = learner.predict(context, actions)
choice = rng.choice(list(range(3)), probs)
learner.learn(context, actions[choice], rewards[choice],
probs[choice], info)
post_learn_rewards = []
for context in contexts[int(.9 * n_examples):]:
actions = [rng.randoms(n_features) for _ in range(n_actions)]
rewards = [
sum([a * c for a, c in zip(action, context)])
for action in actions
]
rewards = [int(r == max(rewards)) for r in rewards]
post_learn_rewards.append(
rng.choice(rewards,
learner.predict(context, actions)[0]))
average_pre_learn_reward = sum(pre_learn_rewards) / len(
pre_learn_rewards)
average_post_learn_reward = sum(post_learn_rewards) / len(
post_learn_rewards)
self.assertAlmostEqual(.33, average_pre_learn_reward, places=2)
self.assertAlmostEqual(.78, average_post_learn_reward, places=2)