def dimension(self):
        """Compute the dimension of the sampling space and identify the slices
        belonging to each stochastic.
        """
        self.dim = 0
        self._slices = {}
        for stochastic in self.stochastics:
            if isinstance(stochastic.value, np.matrix):
                p_len = len(stochastic.value.A.ravel())
            elif isinstance(stochastic.value, np.ndarray):
                p_len = len(stochastic.value.ravel())
            else:
                p_len = 1
            self._slices[stochastic] = slice(self.dim, self.dim + p_len)
            self.dim += p_len
Compute the dimension of the sampling space and identify the slices
        belonging to each stochastic.