  The data analysis of current Cosmic Microwave Background (CMB) experiments
like BOOMERanG or MAXIMA poses severe challenges which already stretch the
limits of current (super-) computer capabilities, if brute force methods are
used. In this paper we present a practical solution to the optimal map making
problem which can be used directly for next generation CMB experiments like
ARCHEOPS and TopHat, and can probably be extended relatively easily to the full
PLANCK case. This solution is based on an iterative multi-grid Jacobi algorithm
which is both fast and memory sparing. Indeed, if there are N_tod data points
along the one dimensional timeline to analyse, the number of operations is
O(N_tod ln N_tod) and the memory requirement is O(N_tod). Timing and accuracy
issues have been analysed on simulated ARCHEOPS and TopHat data, and we discuss
as well the issue of the joint evaluation of the signal and noise statistical
properties.
