* variable x' = M + x, where M is an arbitrarily large (positive)
* value. x' is therefore always non-negative, whatever the value of x.
* Taking as initial sample value x' = 0 corresponds to x = -M,
* variable x' = M + x, where M is an arbitrarily large (positive)
* value. x' is therefore always non-negative, whatever the value of x.
* Taking as initial sample value x' = 0 corresponds to x = -M,