what does a "e" follow with a float number mean?

[zhuzhanhao1991]

float powLU = powf(LU, 1.0e6f);

what the "e6f" does?

[Zhuge]

The e6 portion is scientific notation; the number 1.0e6 is an alternate way of writing 1.0×10⁶. The f on the end is a suffix indicating that the literal is a float, rather than a double.

[JLBorges]

See: http://en.cppreference.com/w/cpp/language/floating_literal