Hi dr. Rick Wicklin, I'm estimating several parameters with proc nlp ,but I get different results every time I run the code and I have no idea whats wrong . here's my code . THANK YOU!!

proc nlp data=PIN;
max logf;
parms alpha delta eb es mu;
bounds alpha>0;
logf = log((1-alpha) * pdf('POISSON',buy, eb) * pdf('POISSON',sell, es) +
alpha * delta * pdf('POISSON',buy, eb) * pdf('POISSON',sell, es+mu) +
alpha * (1-delta) * pdf('POISSON',buy, eb+mu) * pdf('POISSON',sell, es));
run;