  We present an improved formalism for quantum Monte Carlo calculations of
energy derivatives and properties (e.g. the interatomic forces), with a
multideterminant Jastrow-Slater function. As a function of the number $N_e$ of
Slater determinants, the numerical scaling of $O(N_e)$ per derivative we have
recently reported is here lowered to $O(N_e)$ for the entire set of
derivatives. As a function of the number of electrons $N$, the scaling to
optimize the wave function and the geometry of a molecular system is lowered to
$O(N^3)+O(N N_e)$, the same as computing the energy alone in the sampling
process. The scaling is demonstrated on linear polyenes up to C$_{60}$H$_{62}$
and the efficiency of the method is illustrated with the structural
optimization of butadiene and octatetraene with Jastrow-Slater wave functions
comprising as many as 200000 determinants and 60000 parameters.
