Mean posterior matter power-spectrum. The mean and standard deviation of the matter power spectrum have been computed from 8060 density samples of the Markov chain obtained after the warm-up phase shown in Fig. 2. Although the standard deviation is plotted, it is too small to be seen, showing the stability of the posterior power-spectrum. The dashed line indicates the underlying power spectrum and the 1- and 2-σ cosmic variance limit. The algorithm recovers the power-spectrum amplitudes within the 1-σ cosmic variance uncertainty limit throughout the entire range of Fourier modes considered in this work.