def pCN(iterations,
propose,
phi,
kappa_0,
adapt_frequency=None,
adapt_function=None,
progress_object=None,
storage=None):
progress_object = progress.factory(progress_object)
if adapt_frequency is not None and adapt_function is None:
raise Exception(
'Adapt frequency supplied but no adapt function specified.')
# create an empty numpy if the array is not supplied
return_array = storage is None
if storage is None:
storage = st.ArrayStorage(iterations, kappa_0.shape[0])
acceptances = np.empty(iterations, dtype=np.bool)
cur_kappa = kappa_0
cur_phi = as_single_number(phi(cur_kappa))
progress_object.initialise(iterations)
for i in xrange(iterations):
if adapt_frequency is not None and i > 0 and i % adapt_frequency == 0:
propose = adapt_function(propose, storage, acceptances)
try:
new_kappa = propose(cur_kappa)
new_phi = as_single_number(phi(new_kappa))
if np.isnan(new_phi):
progress_object.report_error(
i,
'About to reject proposal because new value of phi is NaN.'
.format(i))
accept = False
else:
alpha = min(1, np.exp(cur_phi - new_phi))
accept = alpha > np.random.uniform()
except Exception as ex:
progress_object.report_error(i, ex)
accept = False
if accept:
cur_kappa = new_kappa
cur_phi = new_phi
storage.add_sample(cur_kappa.ravel())
acceptances[i] = accept
progress_object.update(i, acceptances[:i])
progress_object.update(iterations, acceptances)
if return_array:
return storage.array, acceptances
return storage, acceptances
def rwm(iterations, propose, log_likelihood, log_prior, init_theta, progress_object=None):
progress_object = progress.factory(progress_object)
adapt = hasattr(propose, 'adapt')
if type(init_theta) is np.ndarray:
theta_shape = init_theta.shape[0]
else:
theta_shape = 1
samples = np.empty((iterations, theta_shape))
acceptances = np.empty(iterations, dtype=np.bool)
cur_theta = init_theta
cur_log_likelihood = as_single_number(log_likelihood(cur_theta))
cur_log_prior = as_single_number(log_prior(cur_theta))
progress_object.initialise(iterations)
for i in xrange(iterations):
new_theta = propose(cur_theta)
new_log_prior = as_single_number(log_prior(new_theta))
if np.isinf(new_log_prior) and new_log_prior < 0:
accept = False
else:
try:
new_log_likelihood = log_likelihood(new_theta)
new_log_likelihood = as_single_number(new_log_likelihood)
if np.isnan(new_log_likelihood):
progress_object.report_error(i, 'Proposal is about to be rejected because likelihood is NaN')
accept = False
elif np.isnan(new_log_prior):
progress_object.report_error(i, 'Proposal is about to be rejected because prior is NaN')
accept = False
else:
alpha = min(1, np.exp(new_log_likelihood + new_log_prior - cur_log_likelihood - cur_log_prior))
accept = np.random.uniform() < alpha
except Exception as ex:
accept = False
progress_object.report_error(i, ex)
if accept:
cur_theta = new_theta
cur_log_likelihood = new_log_likelihood
cur_log_prior = new_log_prior
samples[i, :] = cur_theta
acceptances[i] = accept
if adapt:
propose.adapt(i, accept)
progress_object.update(i, acceptances[:(i+1)])
progress_object.update(iterations, acceptances)
return samples, acceptances
def pCN(
iterations, propose, phi, kappa_0, adapt_frequency=None, adapt_function=None, progress_object=None, storage=None
):
progress_object = progress.factory(progress_object)
if adapt_frequency is not None and adapt_function is None:
raise Exception("Adapt frequency supplied but no adapt function specified.")
# create an empty numpy if the array is not supplied
return_array = storage is None
if storage is None:
storage = st.ArrayStorage(iterations, kappa_0.shape[0])
acceptances = np.empty(iterations, dtype=np.bool)
cur_kappa = kappa_0
cur_phi = as_single_number(phi(cur_kappa))
progress_object.initialise(iterations)
for i in xrange(iterations):
if adapt_frequency is not None and i > 0 and i % adapt_frequency == 0:
propose = adapt_function(propose, storage, acceptances)
try:
new_kappa = propose(cur_kappa)
new_phi = as_single_number(phi(new_kappa))
if np.isnan(new_phi):
progress_object.report_error(i, "About to reject proposal because new value of phi is NaN.".format(i))
accept = False
else:
alpha = min(1, np.exp(cur_phi - new_phi))
accept = alpha > np.random.uniform()
except Exception as ex:
progress_object.report_error(i, ex)
accept = False
if accept:
cur_kappa = new_kappa
cur_phi = new_phi
storage.add_sample(cur_kappa.ravel())
acceptances[i] = accept
progress_object.update(i, acceptances[:i])
progress_object.update(iterations, acceptances)
if return_array:
return storage.array, acceptances
return storage, acceptances
def hmc(iterations,
log_pi,
epsilon,
L,
q_0,
grad_log_pi=None,
progress_object=None):
progress_object = progress.factory(progress_object)
if grad_log_pi is None:
try:
import autograd
grad_log_pi = autograd.grad(log_pi)
except Exception as ex:
raise Exception(
'Gradient of log target not passed and unable to use autograd. {}'
.format(ex))
res = np.empty((iterations, q_0.shape[0]))
acceptances = np.empty(iterations, dtype=np.bool)
U = lambda x: -log_pi(x)
grad_U = lambda x: -grad_log_pi(x)
cur_q = q = q_0
progress_object.initialise(iterations)
for i in xrange(iterations):
p = np.random.normal(size=q.shape[0])
cur_p = p
# half step
try:
p -= epsilon * grad_U(q) / 2.
# alternate full steps for position and momentum
for j in xrange(L):
q += epsilon * p
if i != L:
p -= epsilon * grad_U(q)
# now half-step
p -= epsilon * grad_U(q) / 2.
# negate momentum to make the proposal symmetric
p = -p
# evaluate potential and kinetic energies at start and end of trajectory
cur_U = U(cur_q)
cur_K = np.sum(cur_p**2) / 2.
new_U = U(q)
new_K = np.sum(p**2) / 2.
alpha = min(1, np.exp(-new_U + cur_U - new_K + cur_K))
accept = np.random.uniform() < alpha
except Exception as ex:
progress_object.report_error(i, ex)
accept = False
# accept / reject step
if accept:
res[i, :] = q
cur_q = q
else:
res[i, :] = cur_q
acceptances[i] = accept
progress_object.update(i, acceptances[:(i + 1)])
progress_object.update(iterations, acceptances)
return res
def rwm(iterations,
propose,
log_likelihood,
log_prior,
init_theta,
progress_object=None):
progress_object = progress.factory(progress_object)
adapt = hasattr(propose, 'adapt')
if type(init_theta) is np.ndarray:
theta_shape = init_theta.shape[0]
else:
theta_shape = 1
samples = np.empty((iterations, theta_shape))
acceptances = np.empty(iterations, dtype=np.bool)
cur_theta = init_theta
cur_log_likelihood = as_single_number(log_likelihood(cur_theta))
cur_log_prior = as_single_number(log_prior(cur_theta))
progress_object.initialise(iterations)
for i in xrange(iterations):
new_theta = propose(cur_theta)
new_log_prior = as_single_number(log_prior(new_theta))
if np.isinf(new_log_prior) and new_log_prior < 0:
accept = False
else:
try:
new_log_likelihood = log_likelihood(new_theta)
new_log_likelihood = as_single_number(new_log_likelihood)
if np.isnan(new_log_likelihood):
progress_object.report_error(
i,
'Proposal is about to be rejected because likelihood is NaN'
)
accept = False
elif np.isnan(new_log_prior):
progress_object.report_error(
i,
'Proposal is about to be rejected because prior is NaN'
)
accept = False
else:
alpha = min(
1,
np.exp(new_log_likelihood + new_log_prior -
cur_log_likelihood - cur_log_prior))
accept = np.random.uniform() < alpha
except Exception as ex:
accept = False
progress_object.report_error(i, ex)
if accept:
cur_theta = new_theta
cur_log_likelihood = new_log_likelihood
cur_log_prior = new_log_prior
samples[i, :] = cur_theta
acceptances[i] = accept
if adapt:
propose.adapt(i, accept)
progress_object.update(i, acceptances[:(i + 1)])
progress_object.update(iterations, acceptances)
return samples, acceptances
