def calcOutput(self, input):
'''
Run all data points through the neural network
PARAMETERS
----------
input {TxD}: input data, T points of dimensionality D
RETURNS
-------
output {TxK}: output of the network, T points of dimensionality K (number of network outputs)
'''
input = unsqueeze(input,2)
T,D = input.shape
if D != self.D:
raise ValueError("NeuralNet: invalid input dimensions")
# run the input through the network to attain output
output = np.zeros([T, self.K])
# for each input point
for t, i in enumerate(input):
signal = i
for l in self.layers:
signal = l.calcOutput(signal)
output[t,:] = signal
return output
def derivOptCrit(self, O):
'''
PARAMETERS
----------
O {TxD}: observation matrix with a sequence of T observations, each having dimension D
RETURNS
-------
dC / dy {TxD}: derivative of the optimization criterion for each observation
'''
O = unsqueeze(O, 2)
T, D = O.shape
_, lnAlpha, lnC = self._forward(O, scale=True)
lnBeta = self._backward(O, lnC)
# calculate lnP for each observation for each state's emission distribution
# lnP_obs {T, N}
lnP_obs = np.zeros([T, self.N])
for i in range(0, self.N):
lnP_obs[:, i] = self._B[i].calcLnP(O)
# calculate derivative of the optimization criterion for each observation for each state's emission distribution
dlnP = np.zeros([T, self.N, D])
for i in range(0, self.N):
dlnP[:, i, :] = self._B[i].calcDerivLnP(O)
return np.sum(np.exp(lnBeta + lnAlpha - lnP_obs)[:, :, np.newaxis] *
dlnP,
axis=1)
def derivOptCrit(self, O):
'''
PARAMETERS
----------
O {TxD}: observation matrix with a sequence of T observations, each having dimension D
RETURNS
-------
dC / dy {TxD}: derivative of the optimization criterion for each observation
'''
O = unsqueeze(O,2)
T, D = O.shape
_, lnAlpha, lnC = self._forward(O, scale=True)
lnBeta = self._backward(O, lnC)
# calculate lnP for each observation for each state's emission distribution
# lnP_obs {T, N}
lnP_obs = np.zeros([T,self.N])
for i in range(0,self.N):
lnP_obs[:,i] = self._B[i].calcLnP(O)
# calculate derivative of the optimization criterion for each observation for each state's emission distribution
dlnP = np.zeros([T,self.N,D])
for i in range(0,self.N):
dlnP[:,i,:] = self._B[i].calcDerivLnP(O)
return np.sum(np.exp(lnBeta + lnAlpha - lnP_obs)[:,:,np.newaxis] * dlnP, axis=1)
def viterbi(self, O, labels=True):
'''
Calculates the q*, the most probable state sequence corresponding from the observations O.
As the function name suggests, the viterbi algorithm is used.
PARAMETERS
----------
O {TxD}: observation matrix with a sequence of T observations, each having dimension D
labels: whether to return the state labels, or the state indices
RETURNS
-------
pstar: ln probability of q*
qstar {Tx1}: labels/indices of states in q* (normal python array of len T)
'''
O = unsqueeze(O, 2)
T, D = O.shape
# check dimensions of provided observations agree with the trained emission distributions
dim = self._B[0].mu.shape[1]
if D != dim:
raise ValueError(
'GHMM: observation dimension does not agree with the trained emission distributions for the model'
)
# calculate lnP for each observation for each state's emission distribution
# lnP_obs {T, N}
lnP_obs = np.zeros([T, self.N])
for i in range(self.N):
lnP_obs[:, i] = self._B[i].calcLnP(O)
# lnDelta {TxN}: best score along a single path, at time t, accounting for the first t observations and ending in state Si
lnDelta = np.zeros([T, self.N])
# lnPsi {TxN}: arg max of best scores for each t and j state
lnPsi = np.zeros([T, self.N], dtype=np.int)
# Step 1: initialization
lnDelta[0, :] = np.log(self._pi) + lnP_obs[0, :]
# Step 2: recursion
for t in range(1, T):
pTrans = lnDelta[[t - 1], :].T + np.log(self._A)
lnDelta[t, :] = np.max(pTrans, axis=0) + lnP_obs[t, :]
lnPsi[t, :] = np.argmax(pTrans, axis=0)
# Step 3: termination
qstar = [np.argmax(lnDelta[T - 1, :])]
pstar = lnDelta[T - 1, qstar[-1]]
for t in reversed(range(T - 1)):
qstar.append(lnPsi[t + 1, qstar[-1]])
qstar.reverse()
# return labels
if (labels):
qstar = [self._labels[q] for q in qstar]
return pstar, qstar
def viterbi(self, O, labels = True):
'''
Calculates the q*, the most probable state sequence corresponding from the observations O.
As the function name suggests, the viterbi algorithm is used.
PARAMETERS
----------
O {TxD}: observation matrix with a sequence of T observations, each having dimension D
labels: whether to return the state labels, or the state indices
RETURNS
-------
pstar: ln probability of q*
qstar {Tx1}: labels/indices of states in q* (normal python array of len T)
'''
O = unsqueeze(O,2)
T, D = O.shape
# check dimensions of provided observations agree with the trained emission distributions
dim = self._B[0].mu.shape[1]
if D != dim:
raise ValueError('GHMM: observation dimension does not agree with the trained emission distributions for the model')
# calculate lnP for each observation for each state's emission distribution
# lnP_obs {T, N}
lnP_obs = np.zeros([T,self.N])
for i in range(self.N):
lnP_obs[:,i] = self._B[i].calcLnP(O)
# lnDelta {TxN}: best score along a single path, at time t, accounting for the first t observations and ending in state Si
lnDelta = np.zeros([T,self.N])
# lnPsi {TxN}: arg max of best scores for each t and j state
lnPsi = np.zeros([T,self.N], dtype=np.int)
# Step 1: initialization
lnDelta[0,:] = np.log(self._pi) + lnP_obs[0,:]
# Step 2: recursion
for t in range(1,T):
pTrans = lnDelta[[t-1],:].T + np.log(self._A)
lnDelta[t,:] = np.max(pTrans, axis=0) + lnP_obs[t,:]
lnPsi[t,:] = np.argmax(pTrans, axis=0)
# Step 3: termination
qstar = [np.argmax(lnDelta[T-1,:])]
pstar = lnDelta[T-1,qstar[-1]]
for t in reversed(range(T-1)):
qstar.append(lnPsi[t+1,qstar[-1]])
qstar.reverse()
# return labels
if (labels):
qstar = [self._labels[q] for q in qstar]
return pstar, qstar
def _forward(self, O, scale = True):
'''
Calculates the forward variable, alpha: the probability of the partial observation
sequence O1 O2 ... Ot (until time t) and state Si at time t.
PARAMETERS
----------
O {TxD}: observation matrix with a sequence of T observations, each having dimension D
scale {Boolean}: default True
RETURNS
-------
lnP {Float}: log probability of the observation sequence O
lnAlpha {T,N}: log of the forward variable: the probability of the partial observation
sequence O1 O2 ... Ot (until time t) and state Si at time t.
lnC (T,): log of the scaling coefficients for each observation
'''
O = unsqueeze(O,2)
T, D = O.shape
# check dimensions of provided observations agree with the trained emission distributions
dim = self._B[0].mu.shape[1]
if D != dim:
raise ValueError('GHMM: observation dimension does not agree with the trained emission distributions for the model')
# calculate lnP for each observation for each state's emission distribution
# lnP_obs {T, N}
lnP_obs = np.zeros([T,self.N])
for i in range(self.N):
lnP_obs[:,i] = self._B[i].calcLnP(O)
# forward variable, alpha {T,N}
lnAlpha = np.zeros([T,self.N])
# initialize vector of scaling coefficients
lnC = np.zeros(T)
# Step 1: Initialization
lnAlpha[0,:] = np.log(self._pi) + lnP_obs[0,:]
if scale:
lnC[0] = -logsumexp(lnAlpha[0,:])
lnAlpha[0,:] += lnC[0]
# Step 2: Induction
for t in range(1,T):
lnAlpha[t,:] = logsumexp(lnAlpha[[t-1],:].T + np.log(self._A), axis=0) + lnP_obs[t,:]
if scale:
lnC[t] = -logsumexp(lnAlpha[0,:])
lnAlpha[t,:] += lnC[t]
# Step 3: Termination
if scale:
lnP = -np.sum(lnC)
else:
lnP = logsumexp(lnAlpha[T-1,:])
return lnP, lnAlpha, lnC
def _backward(self, O, lnC):
'''
Calculates the backward variable, beta: the probability of the partial observation
sequence 0T OT-1 ... Ot+1 (backwards to time t+1) and State Si at time t+1
PARAMETERS
----------
O {TxD}: observation matrix with a sequence of T observations, each having dimension D
lnC (T,): log of the scaling coefficients for each observation calculated from the forward pass
RETURNS
-------
lnBeta {T,N}: log of the backward variable: the probability of the partial observation
sequence 0T OT-1 ... Ot+1 (backwards to time t+1) and State Si at time t+1
'''
O = unsqueeze(O, 2)
T, D = O.shape
# check dimensions of provided observations agree with the trained emission distributions
dim = self._B[0].mu.shape[1]
if D != dim:
raise ValueError(
'GHMM: observation dimension does not agree with the trained emission distributions for the model'
)
# calculate lnP for each observation for each state's emission distribution
# lnP_obs {T, N}
lnP_obs = np.zeros([T, self.N])
for i in range(0, self.N):
lnP_obs[:, i] = self._B[i].calcLnP(O)
# backward variable, beta {T,N}
# Step 1: Initialization
# since ln(1) = 0
lnBeta = np.zeros([T, self.N]) + lnC[T - 1]
# Step 2: Induction
for t in reversed(range(T - 1)):
lnBeta[t, :] = logsumexp(
np.log(self._A) + lnP_obs[t + 1, :] + lnBeta[t + 1, :],
axis=1) + lnC[t]
return lnBeta
def _backward(self, O, lnC):
'''
Calculates the backward variable, beta: the probability of the partial observation
sequence 0T OT-1 ... Ot+1 (backwards to time t+1) and State Si at time t+1
PARAMETERS
----------
O {TxD}: observation matrix with a sequence of T observations, each having dimension D
lnC (T,): log of the scaling coefficients for each observation calculated from the forward pass
RETURNS
-------
lnBeta {T,N}: log of the backward variable: the probability of the partial observation
sequence 0T OT-1 ... Ot+1 (backwards to time t+1) and State Si at time t+1
'''
O = unsqueeze(O,2)
T, D = O.shape
# check dimensions of provided observations agree with the trained emission distributions
dim = self._B[0].mu.shape[1]
if D != dim:
raise ValueError('GHMM: observation dimension does not agree with the trained emission distributions for the model')
# calculate lnP for each observation for each state's emission distribution
# lnP_obs {T, N}
lnP_obs = np.zeros([T,self.N])
for i in range(0,self.N):
lnP_obs[:,i] = self._B[i].calcLnP(O)
# backward variable, beta {T,N}
# Step 1: Initialization
# since ln(1) = 0
lnBeta = np.zeros([T,self.N]) + lnC[T-1]
# Step 2: Induction
for t in reversed(range(T-1)):
lnBeta[t,:] = logsumexp(np.log(self._A) + lnP_obs[t+1,:] + lnBeta[t+1,:], axis=1) + lnC[t]
return lnBeta
def setData(self, Xtrain, Ytrain):
self.train = unsqueeze(Xtrain,2)
self.target = unsqueeze(Ytrain,2)
def _forward(self, O, scale=True):
'''
Calculates the forward variable, alpha: the probability of the partial observation
sequence O1 O2 ... Ot (until time t) and state Si at time t.
PARAMETERS
----------
O {TxD}: observation matrix with a sequence of T observations, each having dimension D
scale {Boolean}: default True
RETURNS
-------
lnP {Float}: log probability of the observation sequence O
lnAlpha {T,N}: log of the forward variable: the probability of the partial observation
sequence O1 O2 ... Ot (until time t) and state Si at time t.
lnC (T,): log of the scaling coefficients for each observation
'''
O = unsqueeze(O, 2)
T, D = O.shape
# check dimensions of provided observations agree with the trained emission distributions
dim = self._B[0].mu.shape[1]
if D != dim:
raise ValueError(
'GHMM: observation dimension does not agree with the trained emission distributions for the model'
)
# calculate lnP for each observation for each state's emission distribution
# lnP_obs {T, N}
lnP_obs = np.zeros([T, self.N])
for i in range(self.N):
lnP_obs[:, i] = self._B[i].calcLnP(O)
# forward variable, alpha {T,N}
lnAlpha = np.zeros([T, self.N])
# initialize vector of scaling coefficients
lnC = np.zeros(T)
# Step 1: Initialization
lnAlpha[0, :] = np.log(self._pi) + lnP_obs[0, :]
if scale:
lnC[0] = -logsumexp(lnAlpha[0, :])
lnAlpha[0, :] += lnC[0]
# Step 2: Induction
for t in range(1, T):
lnAlpha[t, :] = logsumexp(lnAlpha[[t - 1], :].T + np.log(self._A),
axis=0) + lnP_obs[t, :]
if scale:
lnC[t] = -logsumexp(lnAlpha[0, :])
lnAlpha[t, :] += lnC[t]
# Step 3: Termination
if scale:
lnP = -np.sum(lnC)
else:
lnP = logsumexp(lnAlpha[T - 1, :])
return lnP, lnAlpha, lnC
