Is most of what you do numerical calculations? How much complexity are you willing to spend (in terms of development and maintanance programmer time) to buy a

Is most of what you do numerical calculations? How much complexity are you willing to spend (in terms of development and maintanance programmer time) to buy a factor of 2 speedup to your code execution time in numerically heavy routines? Have you already optimised the hell out of those routines? Unless the answers are "yes", "a lot", and "yes", mixed precision arithmetic is not the answer for you.