Note
Go to the end to download the full example code.
2D examples of exact and entropic unbalanced optimal transport
This example is designed to show how to compute unbalanced and partial OT in POT.
UOT aims at solving the following optimization problem:
\[ \begin{align}\begin{aligned}W = \min_{\gamma} <\gamma, \mathbf{M}>_F + \mathrm{reg}\cdot\Omega(\gamma) + \mathrm{reg_m} \cdot \mathrm{div}(\gamma \mathbf{1}, \mathbf{a}) + \mathrm{reg_m} \cdot \mathrm{div}(\gamma^T \mathbf{1}, \mathbf{b})\\s.t. \gamma \geq 0\end{aligned}\end{align} \]
where \(\mathrm{div}\) is a divergence. When using the entropic UOT, \(\mathrm{reg}>0\) and \(\mathrm{div}\) should be the Kullback-Leibler divergence. When solving exact UOT, \(\mathrm{reg}=0\) and \(\mathrm{div}\) can be either the Kullback-Leibler or the quadratic divergence. Using \(\ell_1\) norm gives the so-called partial OT.
# Author: Laetitia Chapel <laetitia.chapel@univ-ubs.fr>
# License: MIT License
import numpy as np
import matplotlib.pylab as pl
import ot
Generate data
n = 40 # nb samples
mu_s = np.array([-1, -1])
cov_s = np.array([[1, 0], [0, 1]])
mu_t = np.array([4, 4])
cov_t = np.array([[1, -0.8], [-0.8, 1]])
np.random.seed(0)
xs = ot.datasets.make_2D_samples_gauss(n, mu_s, cov_s)
xt = ot.datasets.make_2D_samples_gauss(n, mu_t, cov_t)
n_noise = 10
xs = np.concatenate((xs, (np.random.rand(n_noise, 2) - 4)), axis=0)
xt = np.concatenate((xt, (np.random.rand(n_noise, 2) + 6)), axis=0)
n = n + n_noise
a, b = np.ones((n,)) / n, np.ones((n,)) / n # uniform distribution on samples
# loss matrix
M = ot.dist(xs, xt)
M /= M.max()
Compute entropic kl-regularized UOT, kl- and l2-regularized UOT
reg = 0.005
reg_m_kl = 0.05
reg_m_l2 = 5
mass = 0.7
entropic_kl_uot = ot.unbalanced.sinkhorn_unbalanced(a, b, M, reg, reg_m_kl)
kl_uot = ot.unbalanced.mm_unbalanced(a, b, M, reg_m_kl, div="kl")
l2_uot = ot.unbalanced.mm_unbalanced(a, b, M, reg_m_l2, div="l2")
partial_ot = ot.partial.partial_wasserstein(a, b, M, m=mass)
Plot the results
pl.figure(2)
transp = [partial_ot, l2_uot, kl_uot, entropic_kl_uot]
title = [
"partial OT \n m=" + str(mass),
"$\ell_2$-UOT \n $\mathrm{reg_m}$=" + str(reg_m_l2),
"kl-UOT \n $\mathrm{reg_m}$=" + str(reg_m_kl),
"entropic kl-UOT \n $\mathrm{reg_m}$=" + str(reg_m_kl),
]
for p in range(4):
pl.subplot(2, 4, p + 1)
P = transp[p]
if P.sum() > 0:
P = P / P.max()
for i in range(n):
for j in range(n):
if P[i, j] > 0:
pl.plot(
[xs[i, 0], xt[j, 0]],
[xs[i, 1], xt[j, 1]],
color="C2",
alpha=P[i, j] * 0.3,
)
pl.scatter(xs[:, 0], xs[:, 1], c="C0", alpha=0.2)
pl.scatter(xt[:, 0], xt[:, 1], c="C1", alpha=0.2)
pl.scatter(xs[:, 0], xs[:, 1], c="C0", s=P.sum(1).ravel() * (1 + p) * 2)
pl.scatter(xt[:, 0], xt[:, 1], c="C1", s=P.sum(0).ravel() * (1 + p) * 2)
pl.title(title[p])
pl.yticks(())
pl.xticks(())
if p < 1:
pl.ylabel("mappings")
pl.subplot(2, 4, p + 5)
pl.imshow(P, cmap="jet")
pl.yticks(())
pl.xticks(())
if p < 1:
pl.ylabel("transport plans")
pl.show()
Total running time of the script: (0 minutes 3.701 seconds)