Bad interaction between num_chains and fixed_param sampler #495
Description
Summary:
somewhere late in PR #492 we introduced a bug.
possibly around changing the logic w/r/t behavoir when user tries to explicitly run chains in parallel?
Description:
the following call to sample, given a model which was compiled with stan_threads==True
datagen_fit = datagen_model.sample(iter_sampling=100000, chains=7, parallel_chains=2)
sampler tries to run multi-threaded - resulting CmdStan call is this:
DEBUG:cmdstanpy:running CmdStan, num_threads: 2
DEBUG:cmdstanpy:CmdStan args: ['/Users/mitzi/github/stan-dev/cmdstanpy/test/data/datagen_poisson_glm', 'id=1', 'random', 'seed=27365', 'output', 'file=/var/folders/db/4jnggnf549s42z50bd61jskm0000gq/T/tmpn5muntyf/datagen_poisson_glm-20211112112133.csv', 'method=sample', 'num_samples=100000', 'algorithm=hmc', 'adapt', 'engaged=1', 'num_chains=7']
which craps out because now there are only 2 output CSV files, not the expected 7. investigate logic and fix.
Additional Information:
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