# Error stan.sample() RuntimeError: Initialization failed

**URL:** https://discourse.mc-stan.org/t/error-stan-sample-runtimeerror-initialization-failed/26352
**Category:** Modeling
**Tags:** pystan
**Created:** [February 14, 2022, 10:38pm UTC](https://discourse.mc-stan.org/t/error-stan-sample-runtimeerror-initialization-failed/26352 "2022-02-14T22:38:43Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![pablogalazcares](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/pablogalazcares/32/13676_2.png) [@pablogalazcares](https://discourse.mc-stan.org/u/pablogalazcares)
#### Post date: [February 14, 2022, 10:38pm UTC](https://discourse.mc-stan.org/t/error-stan-sample-runtimeerror-initialization-failed/26352/1 "2022-02-14T22:38:43Z")

</div>

Hi everyone,

I’m a new user of PyStan and I’m trying to replicate a model that a friend built. I’m using Stan v3.3.0 and I’m coding in notebooks (even in .py files the same error raises). My current issue is that I can build the model but I can’t sample it. The raised error is the following:

* * *

Sampling: 0% Sampling: Initialization failed.  
RuntimeError: Initialization failed.

```nohighlight
RuntimeError Traceback (most recent call last)
Input In [235], in <module>
----> 1 model_fit = model_reg.sample(num_chains=1, num_samples=2000, num_warmup=500)

File ~/Dropbox/Doctorado/Paper RIS - Sim Match Bayers/venv/lib/python3.10/site-packages/stan/model.py:89, in Model.sample(self, num_chains, **kwargs)
     61 def sample(self, *, num_chains=4, **kwargs) -> stan.fit.Fit:
     62 """Draw samples from the model.
     63 
     64 Parameters in ``kwargs`` will be passed to the default sample function.
   (...)
     87 
     88 """
---> 89 return self.hmc_nuts_diag_e_adapt(num_chains=num_chains, **kwargs)

File ~/Dropbox/Doctorado/Paper RIS - Sim Match Bayers/venv/lib/python3.10/site-packages/stan/model.py:108, in Model.hmc_nuts_diag_e_adapt(self, num_chains, **kwargs)
     92 """Draw samples from the model using ``stan::services::sample::hmc_nuts_diag_e_adapt``.
     93 
     94 Parameters in ``kwargs`` will be passed to the (Python wrapper of)
   (...)
    105 
    106 """
    107 function = "stan::services::sample::hmc_nuts_diag_e_adapt"
--> 108 return self._create_fit(function=function, num_chains=num_chains, **kwargs)

File ~/Dropbox/Doctorado/Paper RIS - Sim Match Bayers/venv/lib/python3.10/site-packages/stan/model.py:311, in Model._create_fit(self, function, num_chains, **kwargs)
    308 return fit
    310 try:
--> 311 return asyncio.run(go())
    312 except KeyboardInterrupt:
    313 return

File ~/Dropbox/Doctorado/Paper RIS - Sim Match Bayers/venv/lib/python3.10/site-packages/nest_asyncio.py:38, in _patch_asyncio.<locals>.run(main, debug)
     36 task = asyncio.ensure_future(main)
     37 try:
---> 38 return loop.run_until_complete(task)
     39 finally:
     40 if not task.done():

File ~/Dropbox/Doctorado/Paper RIS - Sim Match Bayers/venv/lib/python3.10/site-packages/nest_asyncio.py:81, in _patch_loop.<locals>.run_until_complete(self, future)
     78 if not f.done():
     79 raise RuntimeError(
     80 'Event loop stopped before Future completed.')
---> 81 return f.result()

File /Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/asyncio/futures.py:201, in Future.result(self)
    199 self.__log_traceback = False
    200 if self._exception is not None:
--> 201 raise self._exception
    202 return self._result

File /Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/asyncio/tasks.py:232, in Task.__step( ***failed resolving arguments*** )
    228 try:
    229 if exc is None:
    230 # We use the `send` method directly, because coroutines
    231 # don't have ` __iter__ ` and ` __next__ ` methods.
--> 232 result = coro.send(None)
    233 else:
    234 result = coro.throw(exc)

File ~/Dropbox/Doctorado/Paper RIS - Sim Match Bayers/venv/lib/python3.10/site-packages/stan/model.py:235, in Model._create_fit.<locals>.go()
    233 sampling_output.clear()
    234 sampling_output.write_line("<info>Sampling:</info> <error>Initialization failed.</error>")
--> 235 raise RuntimeError("Initialization failed.")
    236 raise RuntimeError(message)
    238 resp = await client.get(f"/{fit_name}")

RuntimeError: Initialization failed.

```

* * *

Here is my model:

```stan
stan_model = ””” 
data {
    int<lower=0> N_obs; // number of observations
    int N_players; // number of players
    int N_goalkeepers; // number of goalkeepers
    int N_zones; // number of field zones
    int N_times; // number of time frames
    int N_results; // number of types of results
    int N_locations; // number of types home event

    int<lower=1,upper=N_players> player_id[N_obs];
    int<lower=1,upper=N_goalkeepers> goalkeeper_id[N_obs];
    int<lower=1,upper=N_zones> zone_id[N_obs];
    int<lower=1,upper=N_times> time_id[N_obs];
    int<lower=1,upper=N_results> result_id[N_obs];
    int<lower=1,upper=N_locations> location_id[N_obs];

    int goal[N_obs]; // dependent variable
}
parameters {

    real alpha; // intercept

    vector<lower=0,upper=1>[N_players] beta_player; // coefficient associated with each player
    vector[N_goalkeepers] beta_goalkeeper; // coefficient associated with each goalkeeper
    vector[N_zones] beta_zone; // coefficient associated with each zone
    vector[N_times] beta_time; // coefficient associated with each time frame
    vector[N_results] beta_result; // coefficient associated with each result
    vector[N_locations] beta_location; // coefficient associated with each type of localia

}
model {
    // priors
    alpha ~ normal(0,1);
    beta_player ~ beta(3.44,7.34);
    beta_goalkeeper ~ normal(0,0.38);
    beta_zone ~ normal(-0.17,0.58);
    beta_time ~ normal(-0.23,0.37);
    beta_result ~ normal(-0.5,0.5);
    beta_location ~ normal(-0.78,0.6);

    goal ~ bernoulli_logit(alpha + beta_player[player_id] + beta_goalkeeper[goalkeeper_id] +
        beta_zone[zone_id] + beta_time[time_id] + beta_result[result_id] + beta_location[location_id]);

}
"""

```

```nohighlight
data = {"N_obs": len(df_model),
        "N_players": len(df_model.new_id.unique()),
        "N_goalkeepers": len(df_model.glk_id.unique()),
        "N_zones": len(df_model.cat_zone.unique()),
        "N_times": len(df_model.timeFrame.unique()),
        "N_results": len(df_model.cat_res.unique()),
        "N_locations": len(df_model.home_event.unique()),
        "player_id": df_model.new_id.to_list(),
        "goalkeeper_id": df_model.glk_id.to_list(),
        "zone_id": df_model.cat_zone.to_list(),
        "time_id": df_model.timeFrame.to_list(),
        "result_id": df_model.cat_res.to_list(),
        "location_id": df_model.home_event.to_list(),
        "goal": df_model.goal.to_list()
        }

```

Here is the building of the model (which runs well, it raises Building: done without any warning)

```nohighlight
model_reg = stan.build(stan_models, data=data, random_seed=1)

```

Here is the sample of the model that I’m trying run but raises the error.

```nohighlight
model_fit = model_reg.sample(num_chains=1, num_samples=2000, num_warmup=500)

```

* * *

Could you help me to understand what is the error and how can I solve it? Thanks in advance!

---

<div class="post-metadata">

### Author: ![mitzimorris](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/mitzimorris/32/29_2.png) [@mitzimorris](https://discourse.mc-stan.org/u/mitzimorris)
#### Post date: [February 15, 2022, 8:58pm UTC](https://discourse.mc-stan.org/t/error-stan-sample-runtimeerror-initialization-failed/26352/2 "2022-02-15T20:58:32Z")

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don’t understand the error as I’m not a PyStan user, but it’s quite possible that your input data doesn’t match the names/types/shapes of the variables declared in the model’s `data` block.

[CmdStanPy](https://mc-stan.org/cmdstanpy/) is a newer Python interface. it can be installed via conda and will do a better job on error messages.

---

<div class="post-metadata">

### Author: ![ariddell](https://avatars.discourse-cdn.com/v4/letter/a/57b2e6/32.png) [@ariddell](https://discourse.mc-stan.org/u/ariddell)
#### Post date: [February 15, 2022, 10:35pm UTC](https://discourse.mc-stan.org/t/error-stan-sample-runtimeerror-initialization-failed/26352/3 "2022-02-15T22:35:32Z")

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I agree that the error messages are not getting displayed particularly well. All you get is an “Initialization failed.” error.

If you try out CmdStanPy and get a better error message, please report back here. PyStan should display the same thing, at least in theory.