st: asclogit not converging

["Subramanian, Hemang" <Hemang.Subramanian@scheller.gatech.edu>]

Hi 

I am using Stata MP 12.1.

1.I use an alternative specific conditional logit choice model with the following command.
asclogit achoice ratio_simulcast buyer_distance supply  meanpv  price_variability, case(caseid) alternatives(auction_code)
There are about 115962 cases with an average of 9 observations/units per case.

2.The moment I introduce another variable "number_of_centers" into this model as follows:
asclogit achoice ratio_simulcast buyer_distance supply  meanpv  price_variability number_of_centers, case(caseid) alternatives(auction_code)

The model stops converging. The number_of_centers variable is the total number of auction centers, and is a number between 1 and 40, different for each observation.
I tried various combinations, including standardizing the variable, normalizing the variable, etc, but the results never converge - I need help here--

3.---with iter(15) or iter(n) --- option however, I am able to retrieve the corresponding coefficients of all other variables. Is this the correct usage??




warm regards.
Hemang 
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