  The depinning of an elastic line interacting with a quenched disorder is
studied for long range interactions, applicable to crack propagation or
wetting. An ultrametric distance is introduced instead of the Euclidean
distance, allowing for a drastic reduction of the numerical complexity of the
problem. Based on large scale simulations, two to three orders of magnitude
larger than previously considered, we obtain a very precise determination of
critical exponents which are shown to be indistinguishable from their Euclidean
metric counterparts. Moreover the scaling functions are shown to be unchanged.
The choice of an ultrametric distance thus does not affect the universality
class of the depinning transition and opens the way to an analytic real space
renormalization group approach.
