Bug: Vectorization problem in SRVShapeBundle

[ninamiolane]

Describe the bug

from geomstats.geometry.discrete_curves import R2, DiscreteCurves, SRVShapeBundle
INFO: Using numpy backend
dc = DiscreteCurves(k_sampling_points=10, ambient_manifold=R2)
curve1 = dc.random_point()
curve2 = dc.random_point()
bundle = SRVShapeBundle(k_sampling_points=10, ambient_manifold=R2)
bundle.align(curve1, curve2)

gives the error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Volumes/GoogleDrive/My Drive/code/geomstats/geomstats/geometry/discrete_curves.py", line 2133, in align
    return horizontal_path(1.0)
  File "/Volumes/GoogleDrive/My Drive/code/geomstats/geomstats/geometry/discrete_curves.py", line 2070, in horizontal_path
    n_times = len(t)
TypeError: object of type 'float' has no len()

Steps/Code to Reproduce

from geomstats.geometry.discrete_curves import R2, DiscreteCurves, SRVShapeBundle
dc = DiscreteCurves(k_sampling_points=10, ambient_manifold=R2)
curve1 = dc.random_point()
curve2 = dc.random_point()
bundle = SRVShapeBundle(k_sampling_points=10, ambient_manifold=R2)
bundle.align(curve1, curve2)

Expected Behaviour

No error is thrown.

Actual Behaviour

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Volumes/GoogleDrive/My Drive/code/geomstats/geomstats/geometry/discrete_curves.py", line 2133, in align
    return horizontal_path(1.0)
  File "/Volumes/GoogleDrive/My Drive/code/geomstats/geomstats/geometry/discrete_curves.py", line 2070, in horizontal_path
    n_times = len(t)
TypeError: object of type 'float' has no len()

Your environment

Github master version of geomstats.
Python 3.8.10, Mac.

[alebrigant]

I have fixed the bug in the align method of ShapeSrvBundle in PR #1823. However, the way that random points are generated on the space of discrete curves should also be changed, because for now it generate curves that are completely erratic and on which the alignment procedure is sure not to converge.

[alebrigant]

Working example:

import matplotlib.pyplot as plt
import geomstats.backend as gs
from geomstats.geometry.discrete_curves import R2, SRVShapeBundle


parametrized_curve_1 = lambda x: gs.transpose(
    gs.array([1 + 2 * gs.sin(gs.pi * x), 3 + 2 * gs.cos(gs.pi * x)])
)
parametrized_curve_2 = lambda x: gs.transpose(
    gs.array([5 * gs.ones(len(x)), 4 * (1 - x) + 1])
)
sampling_points = gs.linspace(0., 1., 10)
curve1 = parametrized_curve_1(sampling_points)
curve2 = parametrized_curve_2(sampling_points)

bundle = SRVShapeBundle(k_sampling_points=10, ambient_manifold=R2)
curve2_aligned = bundle.align(curve2, curve1)


plt.figure()
plt.plot(curve1[:, 0], curve1[:, 1], 'o-')
plt.plot(curve2_aligned[:, 0], curve2_aligned[:, 1], 'o-')
plt.show()