def find_best_model_initialization(self, num_kernel_samples: int) -> None:
"""
Test `num_kernel_samples` models with sampled kernel parameters. The model's kernel
parameters are then set to the sample achieving maximal likelihood.
:param num_kernel_samples: Number of randomly sampled kernels to evaluate.
"""
@tf.function
def evaluate_loss_of_model_parameters() -> tf.Tensor:
randomize_hyperparameters(self.model)
return self.model.training_loss()
squeeze_hyperparameters(self.model)
current_best_parameters = read_values(self.model)
min_loss = self.model.training_loss()
for _ in tf.range(num_kernel_samples):
try:
train_loss = evaluate_loss_of_model_parameters()
except tf.errors.InvalidArgumentError: # allow badly specified kernel params
train_loss = 1e100
if train_loss < min_loss: # only keep best kernel params
min_loss = train_loss
current_best_parameters = read_values(self.model)
multiple_assign(self.model, current_best_parameters)
def test_multiple_assign_updates_correct_values(model, var_update_dict):
old_value_dict = leaf_components(model).copy()
multiple_assign(model, var_update_dict)
for path, variable in leaf_components(model).items():
if path in var_update_dict.keys():
np.testing.assert_almost_equal(variable.value().numpy(),
var_update_dict[path],
decimal=7)
else:
np.testing.assert_equal(variable.value().numpy(),
old_value_dict[path].value().numpy())
def test_multiple_assign_fails_with_invalid_values(model,
wrong_var_update_dict):
with pytest.raises(ValueError):
multiple_assign(model, wrong_var_update_dict)
def _copy_kernel(kernel: Kernel) -> Kernel:
"""
Returns a copy of the input kernel with the same values but different pointers.
Doesn't check whether or not the tf.Module objects are actually different.
"""
# Case for when the kernel is a sum of multiple kernels
if type(kernel) is Sum:
res = _copy_kernel(kernel.kernels[0])
for sub_kernel in kernel.kernels[1:]:
res += _copy_kernel(sub_kernel)
return res
# Case for when the kernel is a product of multiple kernels
if type(kernel) is Product:
res = _copy_kernel(kernel.kernels[0])
for sub_kernel in kernel.kernels[1:]:
res *= _copy_kernel(sub_kernel)
return res
# Case for when the kernel is convolutional
if type(kernel) is Convolutional:
image_shape = kernel.image_shape
patch_shape = kernel.patch_shape
base_kernel = _copy_kernel(kernel.base_kernel)
colour_channels = kernel.colour_channels
res = Convolutional(_copy_kernel(base_kernel),
image_shape,
patch_shape,
colour_channels=colour_channels)
multiple_assign(res, parameter_dict(kernel))
return res
# Case for when the kernel is a change-point kernel
if type(kernel) is ChangePoints:
kernels = list(map(_copy_kernel, kernel.kernels))
locations = kernel.locations
steepness = kernel.steepness
name = kernel.name
res = ChangePoints(kernels, locations, steepness=steepness, name=name)
multiple_assign(res, parameter_dict(kernel))
return res
# Case for when the kernel is periodic
if type(kernel) is Periodic:
base_kernel = _copy_kernel(kernel.base_kernel)
period = kernel.period
res = Periodic(base_kernel, period=period)
multiple_assign(res, parameter_dict(kernel))
return res
# Case for when the kernel is (an instance of) a linear kernel
if isinstance(kernel, Linear):
variance = kernel.variance
active_dims = kernel.active_dims
options = [Linear, Polynomial]
correct_classes = [o for o in options if type(kernel) is o]
assert len(
correct_classes
) == 1, f"Only one class should match. List of correct classes: {correct_classes}"
if type(kernel) is Polynomial:
# Calls the constructor of the (only) correct kernel class
res = correct_classes[0](variance=variance,
active_dims=active_dims,
degree=kernel.degree)
else:
# Calls the constructor of the (only) correct kernel class
res = correct_classes[0](variance=variance,
active_dims=active_dims)
multiple_assign(res, parameter_dict(kernel))
return res
# Case for when the kernel is an instance of a static kernel
if isinstance(kernel, Static):
active_dims = kernel.active_dims
options = [White, Constant]
correct_classes = [o for o in options if type(kernel) is o]
assert len(
correct_classes
) == 1, f"Only one class should match. List of correct classes: {correct_classes}"
# Calls the constructor of the (only) correct kernel class
res = correct_classes[0](active_dims=active_dims)
multiple_assign(res, parameter_dict(kernel))
return res
# Case for when the kernel is an instance of a stationary kernel
if isinstance(kernel, Stationary):
active_dims = kernel.active_dims
name = kernel.name
variance = kernel.variance
lengthscales = kernel.lengthscales
options = [
SquaredExponential, Cosine, Exponential, Matern12, Matern32,
Matern52, RationalQuadratic
]
correct_classes = [o for o in options if type(kernel) is o]
assert len(correct_classes) == 1, \
"Only one class should match. List of correct classes: {}".format(correct_classes)
# Calls the constructor of the (only) correct kernel class
res = correct_classes[0](variance=variance,
lengthscales=lengthscales,
active_dims=active_dims,
name=name)
multiple_assign(res, parameter_dict(kernel))
return res
raise ValueError(
f"BNQDflow's copy_kernel function doesn't support this kernel type: {type(kernel)}"
)
