[Limdep Nlogit List] non linear mixed logit model

[Grammatikopoulou Ioanna (Luke)]

Hi!
I am applying a non linear mixed logit model. One of the parameters of the non linear function that I want to estimate needs to be positive. How can I impose such a restriction? I used the cml; command but it didn't work. Also, estimation time is quite large (it can be two to three weeks for 250 draws that I have applied). Is there any way to speed up the model estimation?
Here is my syntax:

NLRPLOGIT
    ;Lhs=CHOICE
    ;Choices=BAU,ALT1,ALT2
      ;Pds=6
      ;Labels=b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,r,g
      ;Start=0.22,0.89,0.13,0.12,0.39,-0.01,0.29,0.10,0.08,0.03,0.14,-0.002,0.1,0.5
      ;fcn=b0(n),b1(n),b2(n),b3(n),b4(n),b5(n),b6(n),b7(n),b8(n),b9(n),b10(n)
      ;halton
    ;cml:r>0
      ;draws=250
      ;rpl
    ;Fn1=pv=(1*VERSIO2+g*((1/(1+r)^(D+0))*(1-VERSIO2)+1/(1+r)^(D+1)+1/(1+r)^(D+2)+1/(1+r)^(D+3)+1/(1+r)^(D+4)+1/(1+r)^(D+5)+1/(1+r)^(D+6)+1/
    (1+r)^(D+7)+1/(1+r)^(D+8)+1/(1+r)^(D+9)))
    *annual+(1-annual)
      ;Fn2=Util1=b0*BAU
    +b1*carbon1+b2*carbon2+b3*biod1+b4*biod2+b5*water1+b6*water2+b7*berry1+b8*berry2+b9*energy1+b10*energy2+
    b11*pv*costrecf

    ;Fn3=Util2=b1*carbon1+b2*carbon2+b3*biod1+b4*biod2+b5*water1+b6*water2+b7*berry1+b8*berry2+b9*energy1+b10*energy2+
    b11*pv*costrecf
      ;Model:
    U(BAU)=Util1/U(ALT1, ALT2)=Util2$


Thank you in advance

Kind regards
Ioanna


Ioanna Grammatikopoulou
Post-doc fellow
Natural Resource Institute Finland (LUKE)
Latokartanonkaari 9
FI-00790, Helsinki
Finland
E-mail: ioanna.grammatikopoulou at luke.fi<mailto:ioanna.grammatikopoulou at luke.fi>