The invention provides a multi-channel DAC circuit which provides for correlation between selected ones of the multiple channels such that a single set of calibration coefficients may be used for calibration of multiple channels. Laser hopping over discrete single cavity modes allows long laser coherence length even under dynamic very high speed tuning conditions. In a further aspect, the authentication code includes a serial number for a computer system running the diagnostic. When the populations and the candidate solutions are large for an optimization problem, computing a solution to the optimization problem consumes a large amount of memory.