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log_prob leaves a temporary output directory per call until interpreter exit

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#867 1 commento 0 reazioni 0 assegnatari Vedi su GitHub

@atarutin ci sta già lavorando.

Dal 9/10/2026.

  • #869 di @atarutin — aperta

Valutazione

Difficoltà
2/5
Tempo stimato
1-3 ore
Idoneità per principianti
22/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Ferma
Stack tecnologico
python
Ambito
tooling

Direzione di ricerca

The leak is in CmdStanModel.log_prob in cmdstanpy/model.py, where tempfile.mkdtemp creates an output directory under _TMPDIR that is never removed. Read how temp_single_json cleans up the neighbouring input files, then check the linked pull request #869 before starting, since it already targets this fix. Done means the output directory is removed on both the success and RuntimeError paths, and a test shows the _TMPDIR entry count is unchanged after repeated calls.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Summary

Each call to CmdStanModel.log_prob creates a new directory under cmdstanpy._TMPDIR and never removes it. _TMPDIR is cleaned only at interpreter exit (atexit), so a long-running process accumulates one directory, holding an output.csv, per call.

Where

cmdstanpy/model.py, CmdStanModel.log_prob (1.3.0):

output_dir = tempfile.mkdtemp(prefix=self.name, dir=_TMPDIR)
output = os.path.join(output_dir, "output.csv")
...
result = pd.read_csv(output, comment="#")
return result

Nothing removes output_dir, on either the success path or the RuntimeError path. The data and params files right beside it use temp_single_json(...) context managers and are cleaned up.

Why it matters

We run log_prob once per optimizer start, as a gradient diagnostic, inside a long-lived worker process. A single fit runs hundreds of starts, and the worker runs indefinitely. The directories grow without bound until the process exits.

Today we work around it by calling the compiled program's log_prob method directly through subprocess, with an output directory we own. That means duplicating cmdstanpy's argument handling, which we would rather not do.

Suggested fix

Let log_prob own its output directory for the duration of the call, as the JSON inputs already do:

with tempfile.TemporaryDirectory(prefix=self.name, dir=_TMPDIR) as output_dir:
    output = os.path.join(output_dir, "output.csv")
    ...
    result = pd.read_csv(output, comment="#")
return result

read_csv loads everything before the directory is removed, so the returned DataFrame is unaffected. An optional output_dir= argument, as optimize/sample have, would also let callers keep the CSV when they want it.

We are happy to open a PR with a test, for example asserting that _TMPDIR's entry count is unchanged after N calls.

Versions

cmdstanpy 1.3.0, CmdStan 2.40.0, Python 3.12, Linux x86_64.

Lingua principale
Python
Stelle
198
Fork
82
Merge medio
4g 11h
PR unite (30g)
3

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