bmm_setup: Check whether this machine can fit bmm models

In bmm: Easy and Accessible Bayesian Measurement Models Using 'brms'

Check whether this machine can fit bmm models

Description

Fitting a model with bmm() needs a C++ toolchain (a compiler and make) and a Stan backend, the software that turns the model into a program and samples from it. There are two backends: the R package cmdstanr, which runs CmdStan, a separate program installed with cmdstanr::install_cmdstan(); and the R package rstan. rstan must load with either backend, because brms uses it to store every fit. bmm_setup() checks each of these, prints whether it passed, and gives one fix for every check that failed. It does not install or change anything.

Two checks concern the toolchain. "C++ toolchain" lets R compile a small test file; "CmdStan toolchain" is cmdstanr's own check, which only looks for make and a compiler on the PATH. The second can pass while the first fails, e.g. on a Mac whose command line tools are missing, and the first is the one that decides.

With smoke_test = TRUE, it finally compiles and samples a small two-parameter mixture model (mixture2p()) through bmm(), on the backend bmm() will use. This is the only check that shows the whole chain works. On an Apple Silicon Mac it takes about 10 seconds with cmdstanr and 45 seconds with rstan, and it is skipped when a check it needs has failed. Once every check passes, rerun the bmm() call that failed.

Usage

bmm_setup(smoke_test = TRUE, backend = getOption("brms.backend", NULL))

Arguments

smoke_test	Logical. Compile and sample a small test model? Defaults to TRUE.
backend	The backend to check, "cmdstanr" or "rstan". The default checks the backend bmm() would choose: the brms.backend option if it is set, otherwise cmdstanr whenever the cmdstanr package is installed, even when CmdStan is not, and rstan otherwise.

Value

A data frame of class bmm_setup with one row per check and the columns check, status ("pass", "fail" or "skip"), detail and fix (NA unless the check failed). It prints as a report.

See Also

bmm(), bmm_data_check()

Examples

# checks without compiling anything
bmm_setup(smoke_test = FALSE)

# compiles and samples a small model as well
bmm_setup()

bmm documentation built on Oct. 16, 2026, 9:08 a.m.