expf vs __expf ?

Can anyone tell me which one is faster and what are the differences between those functions?


Generally, the function prefixed with ‘__’ is the faster version and is implemented with an instruction using the special function unit in hardware. The tradeoff is performance for is accuracy. The CUDA Programming Guide, Appendix B lists the error for all of the functions, and you can compare expf() (Table B-1) with __expf() (Table B-3).

What does ULP mean ???

Appendix B-1 p86:

Oups, just found it. :">

Google is my friend…

Sorry i’m quite a newbie to CUDA and fast programmation/ optimization in general.