Function log_map 

pub fn log_map(y: &[f32], curvature: f32) -> Vec<f32>

Logarithmic map: project from Poincare ball to tangent space at origin.

Inverse of the exponential map.

log_0(y) = (2 / sqrt(-c)) * arctanh(sqrt(-c) * ||y||) * y / ||y||

Arguments

• y - Point in the Poincare ball
• curvature - Curvature of the space (negative for hyperbolic)

Returns

Vector in tangent space at origin.