iter_ns_probability
int iter_ns_probability(struct ub_randstate* rnd, int n, int m);
if(!iter_ns_probability(qstate->env->rnd, toget, missing)) {
int iter_ns_probability(struct ub_randstate* rnd, int n, int m);
if(!iter_ns_probability(qstate->env->rnd, toget, missing)) {