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Comparison · Analytics
cmdstanpy vs iris
A side-by-side editorial comparison of cmdstanpy and iris — release velocity, themes, recent moves, and the top alternatives to consider.
Shared themes:python
cmdstanpy vs iris: 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 iris?
Iris ships steadily on a two-a-year cadence, but its feed publishes only pointers.
Iris tags a release candidate roughly every four to five months — 3.13 through 3.16 over the past year — and the cadence is the only thing the feed actually reports. Every entry is the same seven-line template: a line saying this is a release candidate, conda-forge and PyPI install commands, and a link to a 'What's New' page held elsewhere. No release notes reach the feed at all.
cmdstanpy vs iris: 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.
iris
2.5ANALYTICS
Iris ships steadily on a two-a-year cadence, but its feed publishes only pointers.
◆ Current state
Iris tags a release candidate roughly every four to five months — 3.13 through 3.16 over the past year — and the cadence is the only thing the feed actually reports. Every entry is the same seven-line template: a line saying this is a release candidate, conda-forge and PyPI install commands, and a link to a 'What's New' page held elsewhere. No release notes reach the feed at all.
◆ Where it's heading
The version numbers say a mature Met Office library is being maintained on a predictable schedule; nothing in the published entries says what is being maintained. Until the project puts release content in the tag body, its public trail will read as cadence without substance, and readers have to leave the feed to learn anything. The pattern has been identical across four consecutive releases, so it is a deliberate publishing choice rather than an oversight.
◆ Prediction
Expect v3.17.0rc0 around late 2026 on the same schedule, carrying the same boilerplate — the notes will again live on the documentation site rather than in the release entry.
Alternatives to cmdstanpy and iris
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 iris.
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 iris alternatives →
Recent activity from cmdstanpy and iris
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 13d agoirisv3.16.0rc0
- 4mo agoirisv3.15.0rc0
- 9mo agoirisv3.14.0rc0
- 9mo agocmdstanpydiagnose method, sampler timings and faster CSV parsing
- 1y agoirisv3.13.0rc0
- 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 agocmdstanpyLaplace method and Pathfinder exposed from upstream Stan
Frequently asked questions
What is the difference between cmdstanpy and iris?
Both compete on the same themes — python — within Analytics. iris 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 iris?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. iris 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 iris?
Top iris alternatives in Analytics are ranked by recent ship velocity. Browse the "iris alternatives" section above for the current picks, or visit /alternatives/scitools-iris for the full list with editorial commentary on each.