def hmm_expected_states(log_pi0, log_Ps, ll):
T, K = ll.shape
# Make sure everything is C contiguous
to_c = lambda arr: np.copy(arr, 'C') if not arr.flags['C_CONTIGUOUS'] else arr
log_pi0 = to_c(getval(log_pi0))
log_Ps = to_c(getval(log_Ps))
ll = to_c(getval(ll))
alphas = np.zeros((T, K))
forward_pass(log_pi0, log_Ps, ll, alphas)
normalizer = logsumexp(alphas[-1])
betas = np.zeros((T, K))
backward_pass(log_Ps, ll, betas)
expected_states = alphas + betas
expected_states -= logsumexp(expected_states, axis=1, keepdims=True)
expected_states = np.exp(expected_states)
expected_joints = alphas[:-1,:,None] + betas[1:,None,:] + ll[1:,None,:] + log_Ps
expected_joints -= expected_joints.max((1,2))[:,None, None]
expected_joints = np.exp(expected_joints)
expected_joints /= expected_joints.sum((1,2))[:,None,None]
return expected_states, expected_joints, normalizer
def hmm_expected_states(log_pi0, log_Ps, ll):
T, K = ll.shape
# Make sure everything is C contiguous
log_pi0 = to_c(log_pi0)
log_Ps = to_c(log_Ps)
ll = to_c(ll)
alphas = np.zeros((T, K))
forward_pass(log_pi0, log_Ps, ll, alphas)
normalizer = logsumexp(alphas[-1])
betas = np.zeros((T, K))
backward_pass(log_Ps, ll, betas)
expected_states = alphas + betas
expected_states -= logsumexp(expected_states, axis=1, keepdims=True)
expected_states = np.exp(expected_states)
expected_joints = alphas[:-1,:,None] + betas[1:,None,:] + ll[1:,None,:] + log_Ps
expected_joints -= expected_joints.max((1,2))[:,None, None]
expected_joints = np.exp(expected_joints)
expected_joints /= expected_joints.sum((1,2))[:,None,None]
return expected_states, expected_joints, normalizer
def hmm_expected_states(log_pi0, log_Ps, ll, memlimit=2**31):
T, K = ll.shape
# Make sure everything is C contiguous
log_pi0 = to_c(log_pi0)
log_Ps = to_c(log_Ps)
ll = to_c(ll)
alphas = np.zeros((T, K))
forward_pass(log_pi0, log_Ps, ll, alphas)
normalizer = logsumexp(alphas[-1])
betas = np.zeros((T, K))
backward_pass(log_Ps, ll, betas)
# Compute E[z_t] for t = 1, ..., T
expected_states = alphas + betas
expected_states -= logsumexp(expected_states, axis=1, keepdims=True)
expected_states = np.exp(expected_states)
# Compute E[z_t, z_{t+1}] for t = 1, ..., T-1
# Note that this is an array of size T*K*K, which can be quite large.
# To be a bit more frugal with memory, first check if the given log_Ps
# are TxKxK. If so, instantiate the full expected joints as well, since
# we will need them for the M-step. However, if log_Ps is 1xKxK then we
# know that the transition matrix is stationary, and all we need for the
# M-step is the sum of the expected joints.
stationary = (log_Ps.shape[0] == 1)
if not stationary:
expected_joints = alphas[:-1, :, None] + betas[1:, None, :] + ll[
1:, None, :] + log_Ps
expected_joints -= expected_joints.max((1, 2))[:, None, None]
expected_joints = np.exp(expected_joints)
expected_joints /= expected_joints.sum((1, 2))[:, None, None]
else:
# Compute the sum over time axis of the expected joints
# Limit ourselves to approximately 1GB of memory, assuming
# the entries are float64's (8 bytes)
batch_size = int(memlimit / (8 * K * K))
assert batch_size > 0
expected_joints = np.zeros((1, K, K))
for start in range(0, T - 1, batch_size):
stop = min(T - 1, start + batch_size)
# Compute expectations in this batch
tmp = alphas[start:stop, :,
None] + betas[start + 1:stop + 1,
None, :] + ll[start + 1:stop + 1,
None, :] + log_Ps
tmp -= tmp.max((1, 2))[:, None, None]
tmp = np.exp(tmp)
tmp /= tmp.sum((1, 2))[:, None, None]
expected_joints += tmp.sum(axis=0)
return expected_states, expected_joints, normalizer
def test_backward_pass(T=1000, K=5, D=2):
from pyhsmm.internals.hmm_messages_interface import messages_backwards_log
# Make parameters
As = npr.rand(K, K)
As /= As.sum(axis=-1, keepdims=True)
ll = npr.randn(T, K)
# Use pyhsmm to compute
true_betas = np.zeros((T, K))
messages_backwards_log(As, ll, true_betas)
# Use ssm to compute
test_betas = np.zeros((T, K))
backward_pass(As[None, :, :], ll, test_betas)
assert np.allclose(true_betas, test_betas)
def hmm_expected_states(log_pi0, log_Ps, ll, memlimit=2**31):
T, K = ll.shape
# Make sure everything is C contiguous
log_pi0 = to_c(log_pi0)
log_Ps = to_c(log_Ps)
ll = to_c(ll)
alphas = np.zeros((T, K))
forward_pass(log_pi0, log_Ps, ll, alphas)
normalizer = logsumexp(alphas[-1])
betas = np.zeros((T, K))
backward_pass(log_Ps, ll, betas)
# Compute E[z_t] for t = 1, ..., T
expected_states = alphas + betas
expected_states -= logsumexp(expected_states, axis=1, keepdims=True)
expected_states = np.exp(expected_states)
# Compute E[z_t, z_{t+1}] for t = 1, ..., T-1
# Note that this is an array of size T*K*K, which can be quite large.
# To be a bit more frugal with memory, first check if the given log_Ps
# are TxKxK. If so, instantiate the full expected joints as well, since
# we will need them for the M-step. However, if log_Ps is 1xKxK then we
# know that the transition matrix is stationary, and all we need for the
# M-step is the sum of the expected joints.
stationary = (log_Ps.shape[0] == 1)
if not stationary:
expected_joints = alphas[:-1, :, None] + betas[1:, None, :] + ll[
1:, None, :] + log_Ps
expected_joints -= expected_joints.max((1, 2))[:, None, None]
expected_joints = np.exp(expected_joints)
expected_joints /= expected_joints.sum((1, 2))[:, None, None]
else:
# Compute the sum over time axis of the expected joints
expected_joints = np.zeros((K, K))
compute_stationary_expected_joints(alphas, betas, ll, log_Ps[0],
expected_joints)
expected_joints = expected_joints[None, :, :]
return expected_states, expected_joints, normalizer
def test_hmm_mp_perf(T=10000, K=100, D=20):
# Make parameters
pi0 = np.ones(K) / K
Ps = npr.rand(T-1, K, K)
Ps /= Ps.sum(axis=2, keepdims=True)
ll = npr.randn(T, K)
out1 = np.zeros((T, K))
out2 = np.zeros((T, K))
# Run the PyHSMM message passing code
from pyhsmm.internals.hmm_messages_interface import messages_forwards_log, messages_backwards_log
tic = time()
messages_forwards_log(Ps, ll, pi0, out1)
pyhsmm_dt = time() - tic
print("PyHSMM Fwd: ", pyhsmm_dt, "sec")
# Run the SSM message passing code
from ssm.messages import forward_pass, backward_pass
forward_pass(pi0, Ps, ll, out2) # Call once to compile, then time it
tic = time()
forward_pass(pi0, Ps, ll, out2)
smm_dt = time() - tic
print("SMM Fwd: ", smm_dt, "sec")
assert np.allclose(out1, out2)
# Backward pass
tic = time()
messages_backwards_log(Ps, ll, out1)
pyhsmm_dt = time() - tic
print("PyHSMM Bwd: ", pyhsmm_dt, "sec")
backward_pass(Ps, ll, out2) # Call once to compile, then time it
tic = time()
backward_pass(Ps, ll, out2)
smm_dt = time() - tic
print("SMM (Numba) Bwd: ", smm_dt, "sec")
assert np.allclose(out1, out2)
