def test_get_value_function(self):
mm = MockModel(None)
# test PosteriorMean
vf = _get_value_function(mm)
self.assertIsInstance(vf, PosteriorMean)
self.assertIsNone(vf.objective)
# test SimpleRegret
obj = GenericMCObjective(lambda Y: Y.sum(dim=-1))
sampler = IIDNormalSampler(num_samples=2)
vf = _get_value_function(model=mm, objective=obj, sampler=sampler)
self.assertIsInstance(vf, qSimpleRegret)
self.assertEqual(vf.objective, obj)
self.assertEqual(vf.sampler, sampler)
def test_get_value_function(self):
with mock.patch(NO, new_callable=mock.PropertyMock) as mock_num_outputs:
mock_num_outputs.return_value = 1
mm = MockModel(None)
# test PosteriorMean
vf = _get_value_function(mm)
self.assertIsInstance(vf, PosteriorMean)
self.assertIsNone(vf.objective)
# test SimpleRegret
obj = GenericMCObjective(lambda Y: Y.sum(dim=-1))
sampler = IIDNormalSampler(num_samples=2)
vf = _get_value_function(model=mm, objective=obj, sampler=sampler)
self.assertIsInstance(vf, qSimpleRegret)
self.assertEqual(vf.objective, obj)
self.assertEqual(vf.sampler, sampler)
def test_get_value_function(self):
with mock.patch(NO, new_callable=mock.PropertyMock) as mock_num_outputs:
mock_num_outputs.return_value = 1
mm = MockModel(None)
# test PosteriorMean
vf = _get_value_function(mm)
self.assertIsInstance(vf, PosteriorMean)
self.assertIsNone(vf.objective)
# test SimpleRegret
obj = GenericMCObjective(lambda Y, X: Y.sum(dim=-1))
sampler = IIDNormalSampler(num_samples=2)
vf = _get_value_function(model=mm, objective=obj, sampler=sampler)
self.assertIsInstance(vf, qSimpleRegret)
self.assertEqual(vf.objective, obj)
self.assertEqual(vf.sampler, sampler)
# test with project
mock_project = mock.Mock(
return_value=torch.ones(1, 1, 1, device=self.device)
)
vf = _get_value_function(
model=mm,
objective=obj,
sampler=sampler,
project=mock_project,
)
self.assertIsInstance(vf, ProjectedAcquisitionFunction)
self.assertEqual(vf.objective, obj)
self.assertEqual(vf.sampler, sampler)
self.assertEqual(vf.project, mock_project)
test_X = torch.rand(1, 1, 1, device=self.device)
with mock.patch.object(
vf, "base_value_function", __class__=torch.nn.Module, return_value=None
) as patch_bvf:
vf(test_X)
mock_project.assert_called_once_with(test_X)
patch_bvf.assert_called_once_with(
torch.ones(1, 1, 1, device=self.device)
)
def gen_value_function_initial_conditions(
acq_function: AcquisitionFunction,
bounds: Tensor,
num_restarts: int,
raw_samples: int,
current_model: Model,
options: Optional[Dict[str, Union[bool, float, int]]] = None,
) -> Tensor:
r"""Generate a batch of smart initializations for optimizing
the value function of qKnowledgeGradient.
This function generates initial conditions for optimizing the inner problem of
KG, i.e. its value function, using the maximizer of the posterior objective.
Intutively, the maximizer of the fantasized posterior will often be close to a
maximizer of the current posterior. This function uses that fact to generate the
initital conditions for the fantasy points. Specifically, a fraction of `1 -
frac_random` (see options) of raw samples is generated by sampling from the set of
maximizers of the posterior objective (obtained via random restart optimization)
according to a softmax transformation of their respective values. This means that
this initialization strategy internally solves an acquisition function
maximization problem. The remaining raw samples are generated using
`draw_sobol_samples`. All raw samples are then evaluated, and the initial
conditions are selected according to the standard initialization strategy in
'initialize_q_batch' individually for each inner problem.
Args:
acq_function: The value function instance to be optimized.
bounds: A `2 x d` tensor of lower and upper bounds for each column of
task features.
num_restarts: The number of starting points for multistart acquisition
function optimization.
raw_samples: The number of raw samples to consider in the initialization
heuristic.
current_model: The model of the KG acquisition function that was used to
generate the fantasy model of the value function.
options: Options for initial condition generation. These contain all
settings for the standard heuristic initialization from
`gen_batch_initial_conditions`. In addition, they contain
`frac_random` (the fraction of fully random fantasy points),
`num_inner_restarts` and `raw_inner_samples` (the number of random
restarts and raw samples for solving the posterior objective
maximization problem, respectively) and `eta` (temperature parameter
for sampling heuristic from posterior objective maximizers).
Returns:
A `num_restarts x batch_shape x q x d` tensor that can be used as initial
conditions for `optimize_acqf()`. Here `batch_shape` is the batch shape
of value function model.
Example:
>>> fant_X = torch.rand(5, 1, 2)
>>> fantasy_model = model.fantasize(fant_X, SobolQMCNormalSampler(16))
>>> value_function = PosteriorMean(fantasy_model)
>>> bounds = torch.tensor([[0., 0.], [1., 1.]])
>>> Xinit = gen_value_function_initial_conditions(
>>> value_function, bounds, num_restarts=10, raw_samples=512,
>>> options={"frac_random": 0.25},
>>> )
"""
options = options or {}
seed: Optional[int] = options.get("seed")
frac_random: float = options.get("frac_random", 0.6)
if not 0 < frac_random < 1:
raise ValueError(
f"frac_random must take on values in (0,1). Value: {frac_random}")
# compute maximizer of the current value function
value_function = _get_value_function(
model=current_model,
objective=acq_function.objective,
sampler=getattr(acq_function, "sampler", None),
project=getattr(acq_function, "project", None),
)
from botorch.optim.optimize import optimize_acqf
fantasy_cands, fantasy_vals = optimize_acqf(
acq_function=value_function,
bounds=bounds,
q=1,
num_restarts=options.get("num_inner_restarts", 20),
raw_samples=options.get("raw_inner_samples", 1024),
return_best_only=False,
options={
k: v
for k, v in options.items()
if k not in ("frac_random", "num_inner_restarts",
"raw_inner_samples", "eta")
},
)
batch_shape = acq_function.model.batch_shape
# sampling from the optimizers
n_value = int((1 - frac_random) * raw_samples) # number of non-random ICs
if n_value > 0:
eta = options.get("eta", 2.0)
weights = torch.exp(eta * standardize(fantasy_vals))
idx = batched_multinomial(
weights=weights.expand(*batch_shape, -1),
num_samples=n_value,
replacement=True,
).permute(-1, *range(len(batch_shape)))
resampled = fantasy_cands[idx]
else:
resampled = torch.empty(0,
*batch_shape,
1,
bounds.shape[-1],
dtype=bounds.dtype)
# add qMC samples
randomized = draw_sobol_samples(bounds=bounds,
n=raw_samples - n_value,
q=1,
batch_shape=batch_shape,
seed=seed)
# full set of raw samples
X_rnd = torch.cat([resampled, randomized], dim=0)
# evaluate the raw samples
with torch.no_grad():
Y_rnd = acq_function(X_rnd)
# select the restart points using the heuristic
return initialize_q_batch(X=X_rnd,
Y=Y_rnd,
n=num_restarts,
eta=options.get("eta", 2.0))
def gen_one_shot_kg_initial_conditions(
acq_function: qKnowledgeGradient,
bounds: Tensor,
q: int,
num_restarts: int,
raw_samples: int,
options: Optional[Dict[str, Union[bool, float, int]]] = None,
) -> Optional[Tensor]:
r"""Generate a batch of smart initializations for qKnowledgeGradient.
This function generates initial conditions for optimizing one-shot KG using
the maximizer of the posterior objective. Intutively, the maximizer of the
fantasized posterior will often be close to a maximizer of the current
posterior. This function uses that fact to generate the initital conditions
for the fantasy points. Specifically, a fraction of `1 - frac_random` (see
options) is generated by sampling from the set of maximizers of the
posterior objective (obtained via random restart optimization) according to
a softmax transformation of their respective values. This means that this
initialization strategy internally solves an acquisition function
maximization problem. The remaining `frac_random` fantasy points as well as
all `q` candidate points are chosen according to the standard initialization
strategy in `gen_batch_initial_conditions`.
Args:
acq_function: The qKnowledgeGradient instance to be optimized.
bounds: A `2 x d` tensor of lower and upper bounds for each column of
task features.
q: The number of candidates to consider.
num_restarts: The number of starting points for multistart acquisition
function optimization.
raw_samples: The number of raw samples to consider in the initialization
heuristic.
options: Options for initial condition generation. These contain all
settings for the standard heuristic initialization from
`gen_batch_initial_conditions`. In addition, they contain
`frac_random` (the fraction of fully random fantasy points),
`num_inner_restarts` and `raw_inner_samples` (the number of random
restarts and raw samples for solving the posterior objective
maximization problem, respectively) and `eta` (temperature parameter
for sampling heuristic from posterior objective maximizers).
Returns:
A `num_restarts x q' x d` tensor that can be used as initial conditions
for `optimize_acqf()`. Here `q' = q + num_fantasies` is the total number
of points (candidate points plus fantasy points).
Example:
>>> qKG = qKnowledgeGradient(model, num_fantasies=64)
>>> bounds = torch.tensor([[0., 0.], [1., 1.]])
>>> Xinit = gen_one_shot_kg_initial_conditions(
>>> qKG, bounds, q=3, num_restarts=10, raw_samples=512,
>>> options={"frac_random": 0.25},
>>> )
"""
options = options or {}
frac_random: float = options.get("frac_random", 0.1)
if not 0 < frac_random < 1:
raise ValueError(
f"frac_random must take on values in (0,1). Value: {frac_random}")
q_aug = acq_function.get_augmented_q_batch_size(q=q)
# TODO: Avoid unnecessary computation by not generating all candidates
ics = gen_batch_initial_conditions(
acq_function=acq_function,
bounds=bounds,
q=q_aug,
num_restarts=num_restarts,
raw_samples=raw_samples,
options=options,
)
# compute maximizer of the value function
value_function = _get_value_function(
model=acq_function.model,
objective=acq_function.objective,
sampler=acq_function.inner_sampler,
project=getattr(acq_function, "project", None),
)
from botorch.optim.optimize import optimize_acqf
fantasy_cands, fantasy_vals = optimize_acqf(
acq_function=value_function,
bounds=bounds,
q=1,
num_restarts=options.get("num_inner_restarts", 20),
raw_samples=options.get("raw_inner_samples", 1024),
return_best_only=False,
)
# sampling from the optimizers
n_value = int((1 - frac_random) * (q_aug - q)) # number of non-random ICs
eta = options.get("eta", 2.0)
weights = torch.exp(eta * standardize(fantasy_vals))
idx = torch.multinomial(weights, num_restarts * n_value, replacement=True)
# set the respective initial conditions to the sampled optimizers
ics[..., -n_value:, :] = fantasy_cands[idx,
0].view(num_restarts, n_value, -1)
return ics
