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# -*- coding: utf-8 -*-
r"""
================================================
Spherical Sliced-Wasserstein Embedding on Sphere
================================================
Here, we aim at transforming samples into a uniform
distribution on the sphere by minimizing SSW:
.. math::
\min_{x} SSW_2(\nu, \frac{1}{n}\sum_{i=1}^n \delta_{x_i})
where :math:`\nu=\mathrm{Unif}(S^1)`.
"""
# Author: Clément Bonet <clement.bonet@univ-ubs.fr>
#
# License: MIT License
# sphinx_gallery_thumbnail_number = 3
import numpy as np
import matplotlib.pyplot as pl
import matplotlib.animation as animation
import torch
import torch.nn.functional as F
import ot
# %%
# Data generation
# ---------------
torch.manual_seed(1)
N = 500
x0 = torch.rand(N, 3)
x0 = F.normalize(x0, dim=-1)
# %%
# Plot data
# ---------
def plot_sphere(ax):
xlist = np.linspace(-1.0, 1.0, 50)
ylist = np.linspace(-1.0, 1.0, 50)
r = np.linspace(1.0, 1.0, 50)
X, Y = np.meshgrid(xlist, ylist)
Z = np.sqrt(np.maximum(r**2 - X**2 - Y**2, 0))
ax.plot_wireframe(X, Y, Z, color="gray", alpha=0.3)
ax.plot_wireframe(X, Y, -Z, color="gray", alpha=0.3) # Now plot the bottom half
# plot the distributions
pl.figure(1)
ax = pl.axes(projection="3d")
plot_sphere(ax)
ax.scatter(x0[:, 0], x0[:, 1], x0[:, 2], label="Data samples", alpha=0.5)
ax.set_title("Data distribution")
ax.legend()
# %%
# Gradient descent
# ----------------
x = x0.clone()
x.requires_grad_(True)
n_iter = 100
lr = 150
losses = []
xvisu = torch.zeros(n_iter, N, 3)
for i in range(n_iter):
sw = ot.sliced_wasserstein_sphere_unif(x, n_projections=500)
grad_x = torch.autograd.grad(sw, x)[0]
x = x - lr * grad_x / np.sqrt(i / 10 + 1)
x = F.normalize(x, p=2, dim=1)
losses.append(sw.item())
xvisu[i, :, :] = x.detach().clone()
if i % 100 == 0:
print("Iter: {:3d}, loss={}".format(i, losses[-1]))
pl.figure(1)
pl.semilogy(losses)
pl.grid()
pl.title("SSW")
pl.xlabel("Iterations")
# %%
# Plot trajectories of generated samples along iterations
# -------------------------------------------------------
ivisu = [0, 10, 20, 30, 40, 50, 60, 70, 80]
fig = pl.figure(3, (10, 10))
for i in range(9):
# pl.subplot(3, 3, i + 1)
# ax = pl.axes(projection='3d')
ax = fig.add_subplot(3, 3, i + 1, projection="3d")
plot_sphere(ax)
ax.scatter(
xvisu[ivisu[i], :, 0],
xvisu[ivisu[i], :, 1],
xvisu[ivisu[i], :, 2],
label="Data samples",
alpha=0.5,
)
ax.set_title("Iter. {}".format(ivisu[i]))
# ax.axis("off")
if i == 0:
ax.legend()
# %%
# Animate trajectories of generated samples along iteration
# ---------------------------------------------------------
pl.figure(4, (8, 8))
def _update_plot(i):
i = 3 * i
pl.clf()
ax = pl.axes(projection="3d")
plot_sphere(ax)
ax.scatter(
xvisu[i, :, 0], xvisu[i, :, 1], xvisu[i, :, 2], label="Data samples$", alpha=0.5
)
ax.axis("off")
ax.set_xlim((-1.5, 1.5))
ax.set_ylim((-1.5, 1.5))
ax.set_title("Iter. {}".format(i))
return 1
print(xvisu.shape)
i = 0
ax = pl.axes(projection="3d")
plot_sphere(ax)
ax.scatter(
xvisu[i, :, 0],
xvisu[i, :, 1],
xvisu[i, :, 2],
label="Data samples from $G\#\mu_n$",
alpha=0.5,
)
ax.axis("off")
ax.set_xlim((-1.5, 1.5))
ax.set_ylim((-1.5, 1.5))
ax.set_title("Iter. {}".format(ivisu[i]))
ani = animation.FuncAnimation(
pl.gcf(), _update_plot, n_iter // 5, interval=200, repeat_delay=2000
)
# %%
|
