def make_pinwheel_data(num_classes, num_per_class, rate=2.0, noise_std=0.001):
spoke_angles = np.linspace(0, 2*np.pi, num_classes+1)[:-1]
rs = npr.RandomState(0)
x = np.linspace(0.1, 1, num_per_class)
xs = np.concatenate([rate *x * np.cos(angle + x * rate) + noise_std * rs.randn(num_per_class)
for angle in spoke_angles])
ys = np.concatenate([rate *x * np.sin(angle + x * rate) + noise_std * rs.randn(num_per_class)
for angle in spoke_angles])
return np.concatenate([np.expand_dims(xs, 1), np.expand_dims(ys,1)], axis=1)
def make_pinwheel_data(num_spokes=5, points_per_spoke=40, rate=1.0, noise_std=0.005):
"""Make synthetic data in the shape of a pinwheel."""
spoke_angles = np.linspace(0, 2 * np.pi, num_spokes + 1)[:-1]
rs = npr.RandomState(0)
x = np.linspace(0.1, 1, points_per_spoke)
xs = np.concatenate([x * np.cos(angle + x * rate) + noise_std * rs.randn(len(x))
for angle in spoke_angles])
ys = np.concatenate([x * np.sin(angle + x * rate) + noise_std * rs.randn(len(x))
for angle in spoke_angles])
return np.concatenate([np.expand_dims(xs, 1), np.expand_dims(ys,1)], axis=1)
def plot_gmm(params, ax, num_points=100):
angles = np.expand_dims(np.linspace(0, 2*np.pi, num_points), 1)
xs, ys = np.cos(angles), np.sin(angles)
circle_pts = np.concatenate([xs, ys], axis=1) * 2.0
for log_proportion, mean, chol in zip(*unpack_params(params)):
cur_pts = mean + np.dot(circle_pts, chol)
ax.plot(cur_pts[:, 0], cur_pts[:, 1], '-')
def predictions(weights, inputs):
"""weights is shape (num_weight_samples x num_weights)
inputs is shape (num_datapoints x D)"""
inputs = np.expand_dims(inputs, 0)
for W, b in unpack_layers(weights):
outputs = np.einsum('mnd,mdo->mno', inputs, W) + b
inputs = nonlinearity(outputs)
return outputs
def log_marginal_likelihood(params, data):
cluster_lls = []
for log_proportion, mean, chol in zip(*unpack_params(params)):
cov = np.dot(chol.T, chol) + 0.000001 * np.eye(D)
cluster_log_likelihood = log_proportion + mvn.logpdf(data, mean, cov)
cluster_lls.append(np.expand_dims(cluster_log_likelihood, axis=0))
cluster_lls = np.concatenate(cluster_lls, axis=0)
return np.sum(logsumexp(cluster_lls, axis=0))
def unpack_params(params):
"""Unpacks parameter vector into the proportions, means and covariances
of each mixture component. The covariance matrices are parametrized by
their Cholesky decompositions."""
log_proportions = parser.get(params, 'log proportions')
normalized_log_proportions = log_proportions - logsumexp(log_proportions)
means = parser.get(params, 'means')
lower_tris = np.tril(parser.get(params, 'lower triangles'), k=-1)
diag_chols = np.exp( parser.get(params, 'log diagonals'))
chols = []
for lower_tri, diag in zip(lower_tris, diag_chols):
chols.append(np.expand_dims(lower_tri + np.diag(diag), 0))
chols = np.concatenate(chols, axis=0)
return normalized_log_proportions, means, chols
def callback(params, t, g):
print("Iteration {} lower bound {}".format(t, -objective(params, t)))
# Sample functions from posterior.
rs = npr.RandomState(0)
mean, log_std = unpack_params(params)
#rs = npr.RandomState(0)
sample_weights = rs.randn(10, num_weights) * np.exp(log_std) + mean
plot_inputs = np.linspace(-8, 8, num=400)
outputs = predictions(sample_weights, np.expand_dims(plot_inputs, 1))
# Plot data and functions.
plt.cla()
ax.plot(inputs.ravel(), targets.ravel(), 'bx')
ax.plot(plot_inputs, outputs[:, :, 0].T)
ax.set_ylim([-2, 3])
plt.draw()
plt.pause(1.0/60.0)
def rbf_covariance(kernel_params, x, xp):
output_scale = np.exp(kernel_params[0])
lengthscales = np.exp(kernel_params[1:])
diffs = np.expand_dims(x /lengthscales, 1)\
- np.expand_dims(xp/lengthscales, 0)
return output_scale * np.exp(-0.5 * np.sum(diffs**2, axis=2))
return 0.5 * (np.tril(mat) + np.triu(mat, 1).T)
elif len(mat.shape) == 3:
return 0.5 * (np.tril(mat) + np.swapaxes(np.triu(mat, 1), 1,2))
else:
raise ArithmeticError
def generalized_outer_product(mat):
if len(mat.shape) == 1:
return np.outer(mat, mat)
elif len(mat.shape) == 2:
return np.einsum('ij,ik->ijk', mat, mat)
else:
raise ArithmeticError
def covgrad(x, mean, cov):
# I think once we have Cholesky we can make this nicer.
solved = np.linalg.solve(cov, (x - mean).T).T
return lower_half(np.linalg.inv(cov) - generalized_outer_product(solved))
logpdf.defgrad(lambda ans, x, mean, cov: unbroadcast(ans, x, lambda g: -np.expand_dims(g, 1) * np.linalg.solve(cov, (x - mean).T).T), argnum=0)
logpdf.defgrad(lambda ans, x, mean, cov: unbroadcast(ans, mean, lambda g: np.expand_dims(g, 1) * np.linalg.solve(cov, (x - mean).T).T), argnum=1)
logpdf.defgrad(lambda ans, x, mean, cov: unbroadcast(ans, cov, lambda g: -np.reshape(g, np.shape(g) + (1, 1)) * covgrad(x, mean, cov)), argnum=2)
# Same as log pdf, but multiplied by the pdf (ans).
pdf.defgrad(lambda ans, x, mean, cov: unbroadcast(ans, x, lambda g: -g * ans * np.linalg.solve(cov, x - mean)), argnum=0)
pdf.defgrad(lambda ans, x, mean, cov: unbroadcast(ans, mean, lambda g: g * ans * np.linalg.solve(cov, x - mean)), argnum=1)
pdf.defgrad(lambda ans, x, mean, cov: unbroadcast(ans, cov, lambda g: -g * ans * covgrad(x, mean, cov)), argnum=2)
entropy.defgrad_is_zero(argnums=(0,))
entropy.defgrad(lambda ans, mean, cov: unbroadcast(ans, cov, lambda g: 0.5 * g * np.linalg.inv(cov).T), argnum=1)
gamma = primitive(scipy.special.gamma)
gammaln = primitive(scipy.special.gammaln)
gammasgn = primitive(scipy.special.gammasgn)
rgamma = primitive(scipy.special.rgamma)
multigammaln = primitive(scipy.special.multigammaln)
gammasgn.defgrad_is_zero()
polygamma.defgrad_is_zero(argnums=(0,))
polygamma.defgrad(lambda ans, n, x: lambda g: g * polygamma(n + 1, x), argnum=1)
psi.defgrad( lambda ans, x: lambda g: g * polygamma(1, x))
digamma.defgrad( lambda ans, x: lambda g: g * polygamma(1, x))
gamma.defgrad( lambda ans, x: lambda g: g * ans * psi(x))
gammaln.defgrad( lambda ans, x: lambda g: g * psi(x))
rgamma.defgrad( lambda ans, x: lambda g: g * psi(x) / -gamma(x))
multigammaln.defgrad(lambda ans, a, d:
lambda g: g * np.sum(digamma(np.expand_dims(a, -1) - np.arange(d)/2.), -1))
multigammaln.defgrad_is_zero(argnums=(1,))
### Bessel functions ###
j0 = primitive(scipy.special.j0)
y0 = primitive(scipy.special.y0)
j1 = primitive(scipy.special.j1)
y1 = primitive(scipy.special.y1)
jn = primitive(scipy.special.jn)
yn = primitive(scipy.special.yn)
j0.defgrad(lambda ans, x: lambda g: -g * j1(x))
y0.defgrad(lambda ans, x: lambda g: -g * y1(x))
j1.defgrad(lambda ans, x: lambda g: g * (j0(x) - jn(2, x)) / 2.0)
