[Quantlib-users] BlackKarasinski Class in Quantlib

[Brian S. <bri...@gm...>]

Hi,

I am confused about the definition of the Black Karasinski Class
implemented in Quantlib.

The reference is available in
https://rkapl123.github.io/QLAnnotatedSource/d4/d58/class_quant_lib_1_1_black_karasinski.html

As per this documentation, the constructor of this class takes a
parameter called "a" which is defaulted at 0.1

But in this same documentation, the actual process is defined as -

\[ d\ln r_t = (\theta(t) - \alpha \ln r_t)dt + \sigma dW_t, \]

Can you please help me understand what is the relation between a and
{theta, alpha} in above two forms of specification?

Thanks for your time. Regards