Function log1pf 

pub unsafe extern "C" fn log1pf(x: f32) -> f32

Calculate the value of of the input argument x.

Nvidia docs

Returns

• __nv_log1pf( ) returns .
• __nv_log1pf(-1) returns +0.
• __nv_log1pf(x) returns NaN for x < -1.
• __nv_log1pf( ) returns . For accuracy information for this function see the CUDA C Programming Guide, Appendix D.1, Table 6.