### What are peak counts?

**Peaks** are local maxima of the projected mass maps.
They are direct tracers of massive structures and are related to the mass function of the dark matter halo distribution.
This statistic has been shown as a promising tool to constrain cosmological models.

### A new model for prediction

We have developped a prediction model for weak-lensing peak counts using a stochastic forward approach. The summary of the algorithm is as follows:

We have shown that in this way, the prediction agrees well with $N$-body simulations.

Three advantages can be outlined from this model:

**Fast** - only few seconds for creating a 25-deg$^2$ field, without MPI or GPU programming
**Flexible** - straightforward to include observational effects (e.g. photo-$z$ errors, masks) and additional features (e.g. intrinsic alignment, baryonic effects)
**Full PDF information** - allow more flexible constraint methods such as varying covariances, $p$-value evaluation, approximate Bayesian computation, etc.