class HmcArg hmc_arg = {
int steps_per_traj = 5 
double step_size =   0.2
MetropolisType metropolis = METROPOLIS_NO
ReunitarizeType reunitarize = REUNITARIZE_YES
ReverseTest reverse = REVERSE_NO
ReproduceTest reproduce = REPRODUCE_NO
int reproduce_attempt_limit = 3
}