  The precision of the cosmological data allows us to accurately approximate
the predictions for cosmological observables by Taylor expanding up to a low
order the dependence on the cosmological parameters around a reference
cosmology. By applying this observation to the redshift-space one-loop galaxy
power spectrum of the Effective Field Theory of Large-Scale Structure, we
analyze the BOSS DR12 data by scanning over all the parameters of $\Lambda$CDM
cosmology with massive neutrinos. We impose several sets of priors, the widest
of which is just a Big Bang Nucleosynthesis prior on the current fractional
energy density of baryons, $\Omega_b h^2$, and a bound on the sum of neutrino
masses to be less than 0.9 eV. In this case we measure the primordial amplitude
of the power spectrum, $A_s$, the abundance of matter, $\Omega_m$, the Hubble
parameter, $H_0$, and the tilt of the primordial power spectrum, $n_s$, to
about $19\%$, $5.7\%$, $2.2\%$ and $7.3\%$ respectively, obtaining $\ln (
10^{10} A_s) =2.91\pm 0.19$, $\Omega_m=0.314\pm 0.018$, $H_0=68.7\pm 1.5$ km/(s
Mpc) and $n_s=0.979\pm 0.071$ at $68\%$ confidence level. A public code is
released with this preprint.
