  The design of an interferometric array should allow optimal instrumental
response regarding all possible source positions, times of integration and
scientific goals. It should also take into account constraints such as
forbidden regions on the ground due to impracticable topography. The complexity
of the problem requires one to proceed by steps. A possible approach is to
first consider a single observation and a single scientific purpose. A new
algorithm is introduced to solve efficiently this particular problem called the
configuration problem. It is based on the computation of pressure forces
related to the discrepancies between the model (as determined by the scientific
purpose) and the actual distribution of Fourier samples. The flexibility and
rapidity of the method are well adapted to the full array design. A software
named APO that can be used for the design of new generation interferometers
such as ALMA and ATA has been developed.
