  This paper presents a multigrid algorithm for the computation of the rank-R
canonical decomposition of a tensor for low rank R. Standard alternating least
squares (ALS) is used as the relaxation method. Transfer operators and
coarse-level tensors are constructed in an adaptive setup phase based on
multiplicative correction and on Bootstrap algebraic multigrid. An accurate
solution is then computed by an additive solve phase based on the Full
Approximation Scheme. Numerical tests show that for certain test problems the
multilevel method significantly outperforms standalone ALS when a high level of
accuracy is required.
