  We describe an efficient implementation of the BCFW recursion relations for
tree-amplitudes in N=4 super Yang-Mills, which can generate analytic formulae
for general N^kMHV colour-ordered helicity-amplitudes-which, in particular,
includes all those of non-supersymmetric Yang-Mills. This note accompanies the
public release of the Mathematica package "bcfw", which can quickly (and
automatically) generate these amplitudes in a form that should be easy to
export to any computational framework of interest, or which can be evaluated
directly within Mathematica given external states specified by four-momenta,
spinor-helicity variables or momentum-twistors. Moreover, bcfw is able to solve
the BCFW recursion relations using any one of a three-parameter family of
recursive `schemes,' leading to an extremely wide variety of distinct analytic
representations of any particular amplitude. This flexibility is made possible
by bcfw's use of the momentum-twistor Grassmannian integral to describe all
tree amplitudes; and this flexibility is accompanied by a remarkable increase
in efficiency, leading to formulae that can be evaluated much faster-often by
several orders of magnitude-than those previously derived using BCFW.
