The typedef float_fast#_t, with # replaced by the width, designates the fastest floating-point type with a width of at least # bits.

There is no absolute guarantee that these types are the fastest for all purposes. In any case, however, they satisfy the precision and width requirements.

Fastest minimum-width floating-point types are provided for all existing exact-width floating-point types on a given platform.

For example, if a platform supports float32_t and float64_t, then float_fast32_t and float_fast64_t will also be supported, etc.