Choice of sampler

Dear users,

Reading through Stan’s documentation under heading Sampling i would like to know about the following statement
“For continuous parameters, Stan uses Hamiltonian Monte Carlo (HMC) sampling”

  1. For a real parameter defined in the parameters{ } block does the stan( ) function automatically selects HMC sampler if algorithm is not specified?
parameters {
real theta;
theta ~ normal(0 , 1);

And use

fit <- stan("modelcode",
             data = stan_data,
             chains = 1, iter = 100, 
             warmup = 50,
  1. If algorithm is not specified, the output of print( ) says “samples are draws using NUTS(diag_e)”. Then, if the parameter estimated is real, does this output means that the result we get from the default stan( ) function is incorrect? or do we need to specify algorithm = c(“HMC”) in the stan( ) function?

  2. Is it legal to specify more than one algorithm at the same time? For example: algorithm = c(“NUTS”, “HMC”, “Fixed_param”) .


After reading through

I now understand that NUTS is a variant of HMC used in Stan.

I should have read more carefully.

By default Stan uses NUTS. It’s one variant of HMC, so sometimes NUTS gets called an HMC or whatnot. There have been various NUTS versions as well. It’s all a little confusing :D.

To the third question, you only get to use one algorithm at a time.

@bbbales2, Thanks for clearing this.