st: moptimze: what's the difference of these practices

[Sun Yutao <yutao.sun.statalist@outlook.com>]

Hi,

I¡¯m working with -moptimize()- and I just want know what¡¯s the difference 
between directly using the parameter feed by the -moptimize()- and 
using -moptimize_util_xb()-

I have a callback function say: feval(M,p,v) and when I'm using the p directly 
to compute the log-likelihood it always says "could not calculate numerical 
derivatives -- flat or discontinuous region encountered", but according to the 
help file: " The second argument, b (p in my function), is the entire 
coefficient vector". Here is an example of how I would compute the 
xb: -xb=XB*p[1::4]':+p[5]-   (4 x*b + a cons)

But when I switch to -xb=moptimize_util_xb(M,b,1)-, everything is ok again...

Does anyone know the difference of these two?

Best regards,
Sun Yutao




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