Tensor train summation without loss of accuracy.
Sums buffered tensor trains in a single tensor train using AMEn algorithm.
x - ttclass with buffered rank-one tensors tol - relative tolerance parameter, e.g. 1e-10 The opts field is optional: opts.max_swp - maximum number of iterations opts.init_guess_rank - rank of the initial guess opts.enrichment_rank - rank of the enrichment opts.verb - verbosity switch
y - ttclass with a single tensor train, such that |x-y|<tol*|x| in Frobenius norm
Summation is a messy operation in TT format. Spinach buffers tensor train sums and processes them in batches using this function.