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Comparison · Analytics
cmdstanpy vs OpenMC
A side-by-side editorial comparison of cmdstanpy and OpenMC — release velocity, themes, recent moves, and the top alternatives to consider.
cmdstanpy vs OpenMC: at a glance
What is cmdstanpy?
CmdStanPy is clearing deprecations ahead of a 2.0 it keeps announcing.
CmdStanPy is at v1.3.0, which added a diagnose method on CmdStanModel, sampler timing information, create_inits() across the stanfit classes, and much faster MCMC CSV parsing. Every release in this window opens with the same notice: the next non-bugfix release will be 2.0 and will remove existing deprecations. In line with that, 1.3.0 drops Python 3.8 and renames the metric argument to inv_metric.
What is OpenMC?
OpenMC's random ray solver has gone from new arrival to the centre of every release
OpenMC is a Monte Carlo particle transport code for neutronics and radiation analysis. Since the random ray transport solver landed in 0.15.0 it has received substantial work in every subsequent release, most recently local adjoint sources, temperature and distributed-density feedback, fission-heating tallies and a weight-window bootstrapping workflow. The other consistent thread is shutdown-dose and depletion tooling, where 0.15.3 introduced an R2SManager to automate the rigorous two-step workflow and 0.16.0 extended it with reactivity control, CRAM substeps and multiple meshes.
cmdstanpy vs OpenMC: editorial side-by-side
cmdstanpy
0.0ANALYTICS
CmdStanPy is clearing deprecations ahead of a 2.0 it keeps announcing.
◆ Current state
CmdStanPy is at v1.3.0, which added a diagnose method on CmdStanModel, sampler timing information, create_inits() across the stanfit classes, and much faster MCMC CSV parsing. Every release in this window opens with the same notice: the next non-bugfix release will be 2.0 and will remove existing deprecations. In line with that, 1.3.0 drops Python 3.8 and renames the metric argument to inv_metric.
◆ Where it's heading
The package tracks upstream Stan and prepares for its own break. New inference methods arrive as Stan ships them — Laplace with Stan 2.32, Pathfinder with 2.33 — while the interface work is mostly deprecation staging and CSV input-output performance. The repeated 2.0 warning across two years of releases suggests the cut has been deferred more than once.
◆ Prediction
The notice at the top of every release points to 2.0 as the next non-bugfix version, removing the deprecations staged here including the metric argument.
OpenMC
2.5ANALYTICS
OpenMC's random ray solver has gone from new arrival to the centre of every release
◆ Current state
OpenMC is a Monte Carlo particle transport code for neutronics and radiation analysis. Since the random ray transport solver landed in 0.15.0 it has received substantial work in every subsequent release, most recently local adjoint sources, temperature and distributed-density feedback, fission-heating tallies and a weight-window bootstrapping workflow. The other consistent thread is shutdown-dose and depletion tooling, where 0.15.3 introduced an R2SManager to automate the rigorous two-step workflow and 0.16.0 extended it with reactivity control, CRAM substeps and multiple meshes.
◆ Where it's heading
The project is layering a deterministic-adjacent solver alongside its Monte Carlo core rather than replacing it, and the ratio of random-ray work to core-solver work in each release keeps rising. In parallel it is packaging expert workflows into objects — R2SManager is the clearest case, turning a multi-stage shutdown dose calculation into a class rather than a recipe. The Python API is where most of that packaging surfaces, and it is also where the compatibility breaks land, with the minimum version moving to 3.12 in 0.16.0.
◆ Prediction
Given that every release since 0.15.0 has expanded the random ray solver's feedback and tally coverage, the next is likely to continue closing the gap between it and the main solver's feature set. The notes do not indicate whether it is intended to become a default path.
Alternatives to cmdstanpy and OpenMC
Other Analytics products tracked by Sparkpulse, ranked by recent ship velocity. Each card links to a full editorial trajectory and lets you pivot into a head-to-head comparison with either cmdstanpy or OpenMC.
modeltime
modeltime built conformal intervals in, then went quiet on features.
performance
performance keeps adding ways to check a model you have already fitted.
dowhy
DoWhy adds one estimation method a year and keeps its identification edge.
OpenHouse
OpenHouse is hardening the seams where table policies and jobs quietly fail.
silx
silx 3.0 moved its default Qt binding to PySide6 — a migration for everyone embedding it.
See all cmdstanpy alternatives → · See all OpenMC alternatives →
Recent activity from cmdstanpy and OpenMC
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 6d agoOpenMCSurface-flux tallies and PDG particle identifiers in OpenMC 0.16.0
- 8mo agoOpenMCR2SManager automates shutdown dose rate calculations in OpenMC 0.15.3
- 9mo agocmdstanpydiagnose method, sampler timings and faster CSV parsing
- 1y agoOpenMCOpenMC 0.15.2 hotfixes an MPI regression
- 1y agoOpenMCRay-traced material volumes and Phong-shaded plots in OpenMC 0.15.1
- 2y agoOpenMCOpenMC 0.15.0 introduces a random ray transport solver ⚡
- 2y agocmdstanpyFixes from_csv() for CmdStan 2.35 and later
- 2y agocmdstanpyCmdStan 2.35 test fixes and multi-chain profile output
- 2y agocmdstanpypyproject.toml build and pathfinder() argument fixes
- 2y agocmdstanpyNew Pathfinder arguments and warmup without adaptation
- 2y agoOpenMCWeight window generation and continuous nuclide feed in OpenMC 0.14.0
- 2y agocmdstanpyLaplace method and Pathfinder exposed from upstream Stan
Frequently asked questions
What is the difference between cmdstanpy and OpenMC?
They serve adjacent needs but don't currently overlap on shipped themes. OpenMC is currently shipping more aggressively (velocity 2.5 vs 0.0), with 0 editorial sparks in the last 30 days against 0. See the at-a-glance table above for a side-by-side breakdown of velocity, recent sparks, and editorial themes.
Is cmdstanpy better than OpenMC?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. OpenMC is currently shipping more aggressively (velocity 2.5 vs 0.0), with 0 editorial sparks in the last 30 days against 0. For your specific use case, the alternatives sections above list other Analytics products to evaluate alongside.
What are the best alternatives to cmdstanpy?
Top cmdstanpy alternatives in Analytics are ranked by recent ship velocity. Browse the "cmdstanpy alternatives" section above for the current picks, or visit /alternatives/cmdstanpy for the full list with editorial commentary on each.
What are the best alternatives to OpenMC?
Top OpenMC alternatives in Analytics are ranked by recent ship velocity. Browse the "OpenMC alternatives" section above for the current picks, or visit /alternatives/openmc for the full list with editorial commentary on each.