Source code for geometry.manifolds.product_manifold

from contracts import contract
import numpy as np

from .differentiable_manifold import DifferentiableManifold

__all__ = ['ProductManifold']


class ProductManifold(DifferentiableManifold):

    @contract(components='seq[>=2,N]($DifferentiableManifold)',
              weights='None|array[N](>0)')
    def __init__(self, components, weights=None):
        dim = sum([m.dimension for m in components])
        DifferentiableManifold.__init__(self, dimension=dim)
        self.components = components
        if weights is None:
            weights = np.ones(len(components))
        self.weights = weights

    @contract(a='seq')
    def belongs(self, a):
        if not len(a) == len(self.components):  # XXX: what should I throw?
            raise ValueError('I expect a sequence of length %d, not %d.' %
                             (len(a), len(self.components)))
        for x, m in zip(a, self.components):
            m.belongs(x)

    def distance(self, a, b):
        ''' Computes the geodesic distance between two points. '''
        distances = [m.distance(x, y) for x, y, m in zip(a, b, self.components)]
        distances = np.array(distances)
        return (distances * self.weights).sum()

    def logmap(self, base, p):
        ''' Computes the logarithmic map from base point *a* to target *b*. '''
        raise ValueError('Not implemented')  # FIXME: finish this

    def expmap(self, bv):
        raise ValueError('Not implemented')  # FIXME: finish this

    def project_ts(self, bv):
        raise ValueError('Not implemented')  # FIXME: finish this

    def __repr__(self):
        return 'P(%s)' % "x".join([str(x) for x in self.components])