Stan development repository. The master branch contains the current release. The develop branch contains the latest stable development. See the Developer Process Wiki for details.
C-Rank Grade: A (Welcoming) - 67/100
External PR Merge Rate: 65%
Response Time: -
First Timer Success: 67%
stan-dev/stan has a recorded first-timer success rate of 66.7%. Repositories ranked A typically provide actionable feedback during code reviews and actively nurture new community contributors.
Maintainers in stan-dev/stan respond to incoming external pull requests in approximately 0.0 hours on average. Keeping PRs focused on single tasks and ensuring tests pass helps maintainers review faster.
The C-Rank™ system evaluates GitHub projects on a 0–100 scale using real data: PR merge rates, review turnaround time, active maintainer presence, and first-time contributor success. A score of 66.8 places stan-dev/stan in the A tier.
The external contributor pull request merge rate for stan-dev/stan is 64.7%, based on public PR activity from non-core contributors.
stan-dev/stan currently has 2 active issue(s) tagged with beginner-friendly labels like "good first issue", "beginner", or "up-for-grabs".
Highly welcoming maintainers in stan-dev/stan. Prompt code reviews with positive guidance for new contributors.
Discussions in stan-dev/stan focus heavily on practical implementation feedback, code formatting standards, and issue reproduction details.
Unlinked PRs without issue context and changes that fail automated test suites face the highest review friction.
Average Response Latency
Tracks hours until a maintainer leaves a review, comment, or PR response.
External Acceptance Rate
Percentage of community pull requests successfully merged into main.
First PR Conversion
Rate at which developers submitting their first repository PR succeed.
Show contributors that your repository actively reviews and merges external pull requests.
[](https://getmerged.abhishekco.de/stan-dev/stan?utm_source=github&utm_medium=badge)
Historical health & responsiveness evolution
External PR acceptance
First PR success rate
50% receive response in
90% receive response in
Maintainer review activity heatmap & prime window prediction
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Detected: UTC
Maintainers are most responsive around 02:00 UTC (02:00 UTC in your timezone). Recommended submission window is Tuesday - Thursday from 12:00 to 16:00 UTC (12:00 - 16:00 UTC local).
Maintainer Strategy: Maintainer Sweet Spot: PRs under 150 lines merge in ~16 hours (81% approval). Large PRs (>500 lines) take ~115 hours (29% approval). Keep your diff compact for rapid review.
As discussed on the forums, @sims1253 found several ways to remove short-lived repeated allocations in our NUTS code, see sims1253#1 This is consistent with observations that @bob-carpenter and I have made in walnutpie, where it appears to outperform Stan even when using settings designed to make it as similar as possible to Stan's implementation of NUTS. We suspected memory allocations, which walnutpie is quite careful with, to be one possible source
CmdStan writes the inverse metric to a file, but it doesn't include the names of the unconstrained parameters corresponding to the rows/columns. See stan-dev/cmdstanr#716. To do that I think it would just involve including the names returned by model.unconstrained_param_names(names, false, false); in the JSON file, right? For example, { "stepsize": 0.1, "metric_type": "diag_e", "unconstrained_param_names": ["alpha", "beta.1", "beta.2"], "inv_metric": [0.1, 0.2, 0.3] } This would make it much easier for users to figure out which unconstrained parameter elements correspond to which elements of the matrix.
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When evaluating whether to contribute to stan-dev/stan, response velocity and maintainer engagement are crucial. GetMerged continuously tracks pull request trajectories, first-comment latency, and code review rounds to help developers avoid submitting pull requests to backlogged repositories.
Currently, maintainers of stan-dev/stan acknowledge new external contributions in approximately -. Out of all submitted pull requests from non-core authors in the last 180-day window, 64.7% were successfully merged into the primary branch.
stan-dev/stan has a recorded first-timer success rate of 66.7%. Repositories ranked Welcoming typically provide actionable feedback during code reviews and actively nurture new community contributors.
The initial maintainer response time averages ~-. Keeping PRs scoped to single concerns and ensuring CI checks succeed will optimize review turnaround.
The C-Rank™ index scores repositories on a 0 to 100 scale using an objective formula: external PR merge rates, initial response speed, active maintainer count, and first-time contributor retention. A score of 66.8 places stan-dev/stan in the Welcoming tier.
The external pull request merge rate is 64.7%. GetMerged isolates non-core community contributions so external developers get an accurate benchmark of PR acceptance probability.
Yes, stan-dev/stan currently has 2 active issue(s) tagged with beginner-friendly labels. You can inspect these directly from the repository issues tab.
All metrics displayed for stan-dev/stan are automatically retrieved via the public GitHub API and recalculated daily. Insider pull requests submitted by repository owners or organization members are excluded from merge rate calculations to preserve objective external contributor statistics.