rollupTree
The recursive-computation engine under massProps grows the accessors its consumer needed
Comparison · Infra & APIs
modsem vs Skipper
A side-by-side editorial comparison of modsem and Skipper — release velocity, themes, recent moves, and the top alternatives to consider.
modsem vs Skipper: at a glance
What is modsem?
modsem is grinding latent interaction models toward Mplus parity, one estimator at a time.
modsem fits interaction and quadratic effects between latent variables in R, offering both product-indicator approaches (modsem_pi) and distribution-analytic ones (modsem_da, covering LMS and QML). Releases land roughly monthly and are dense pull-request lists. The recent line is dominated by the LMS approach: gradient refactors, parallel E-steps, composite construct support, and careful handling of residual covariances between latent variables.
What is Skipper?
Skipper trims a 4x memory regression out of routesrv, days after shipping h2c
Zalando's HTTP router ships patch tags almost daily, and most carry a single dependency bump or a one-line auth fix. The substance in this window is v0.27.63, which stops routesrv holding an uncompressed route tree alongside the compressed buffer: retained memory in the release's own benchmark falls from 30.7 MB to 2.0 MB, undoing most of the 4x increase zone-aware routing had introduced. Around it sit narrow auth repairs, and an eskip parser change that finally accepts negative numeric arguments in predicates and filters.
modsem vs Skipper: editorial side-by-side
modsem
0.0INFRA · APIS
modsem is grinding latent interaction models toward Mplus parity, one estimator at a time.
◆ Current state
modsem fits interaction and quadratic effects between latent variables in R, offering both product-indicator approaches (modsem_pi) and distribution-analytic ones (modsem_da, covering LMS and QML). Releases land roughly monthly and are dense pull-request lists. The recent line is dominated by the LMS approach: gradient refactors, parallel E-steps, composite construct support, and careful handling of residual covariances between latent variables.
◆ Where it's heading
Two things are being closed at once. The modelling gap — composites and formative constructs, categorical estimators, residual covariances in every direction, multigroup and clustered designs — brings modsem toward what commercial Mplus users expect, and the package's Mplus bridge is maintained alongside it, now with unique file IDs and a cleanup argument. The performance gap is the other: memoised H0, parallel E-step, optimized gradients and Hessians for both LMS and QML, all aimed at the distribution-analytic estimators that are expensive by construction. Convention borrowing from lavaan continues in message formatting and standard-error defaults.
◆ Prediction
The 1.0.20 and 1.0.21 releases both spent effort on residual covariances between endogenous and exogenous latent variables across estimation, prediction and standardization, and that thread has not obviously closed. The arrival of a second contributor moving MplusAutomation to Suggests suggests dependency trimming continues.
Skipper
5.0INFRA · APIS
Skipper trims a 4x memory regression out of routesrv, days after shipping h2c
◆ Current state
Zalando's HTTP router ships patch tags almost daily, and most carry a single dependency bump or a one-line auth fix. The substance in this window is v0.27.63, which stops routesrv holding an uncompressed route tree alongside the compressed buffer: retained memory in the release's own benchmark falls from 30.7 MB to 2.0 MB, undoing most of the 4x increase zone-aware routing had introduced. Around it sit narrow auth repairs, and an eskip parser change that finally accepts negative numeric arguments in predicates and filters.
◆ Where it's heading
Two threads run through the recent tags. The data path keeps getting real work - leastRequests balancing, then h2c end to end in v0.27.57, now the memory cost of zone-aware routing being paid back. The auth filters, by contrast, are only being maintained: token introspection, grant auth, and now the OIDC Referer handling are fixes rather than new capability, and several are follow-ups to each other rather than independent bugs.
◆ Prediction
Zone-aware routing looks like the source of the recent memory attention, so expect further tuning around route storage and the hash computation done on every pull, which the release's second benchmark already isolates. The OIDC cookie change is the second link in an auth chain that started with the grant-auth fix, and is likely to draw another follow-up.
Alternatives to modsem and Skipper
Other Infra & APIs 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 modsem or Skipper.
massProps
A mass-properties rollup spends a year on documentation and follows its sibling's API
writeAlizer
Six months of releases and not one of them touched the scoring models
samplr
A cognitive-science sampling package ships once, then goes quiet for eighteen months
stochvol
A Bayesian volatility sampler in its maintenance decade, paying for its own speed
midr
A black-box interpreter reaches CRAN, then learns multi-class and survival responses
See all modsem alternatives → · See all Skipper alternatives →
Recent activity from modsem and Skipper
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 1d agoSkipperMove OIDC flow protection from Referer to cookies
- 1d agoSkipperv0.27.63: Store routes compressed-only, decompress on demand (#4198)
- 1d agoSkipperEskip predicates and filters accept negative numbers
- 2d agoSkipperFix token introspection handling
- 2d agoSkipperFix grant auth flow
- 2d agoSkipperUpdate outdated golang.org/x dependencies
- 1mo agomodsemUnique Mplus file IDs, cleanup argument, LMS gradient refactor
- 2mo agomodsemComposite constructs for LMS, plus MC-LMS-CAT and MC-QML-CAT
- 3mo agomodsemPrint spacing and a partial-match fix in getSortedEtas()
- 4mo agomodsemCategorical argument for Mplus; partial support for the <~ operator
- 5mo agomodsemConsistent three-way interaction estimates with rcs=TRUE
- 6mo agomodsemSecondary pruning and a forward-difference Hessian mode
Frequently asked questions
What is the difference between modsem and Skipper?
They serve adjacent needs but don't currently overlap on shipped themes. Skipper is currently shipping more aggressively (velocity 5.0 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 modsem better than Skipper?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Skipper is currently shipping more aggressively (velocity 5.0 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 Infra & APIs products to evaluate alongside.
What are the best alternatives to modsem?
Top modsem alternatives in Infra & APIs are ranked by recent ship velocity. Browse the "modsem alternatives" section above for the current picks, or visit /alternatives/modsem for the full list with editorial commentary on each.
What are the best alternatives to Skipper?
Top Skipper alternatives in Infra & APIs are ranked by recent ship velocity. Browse the "Skipper alternatives" section above for the current picks, or visit /alternatives/skipper for the full list with editorial commentary on each.