Papers › Simplified State Space Layers for Sequence Modeling
Simplified State Space Layers for Sequence Modeling
Jimmy T. H. Smith, Andrew Warrington, Scott W. Linderman
Models using structured state space sequence (S4) layers have achieved state-of-the-art performance on long-range sequence modeling tasks. An S4 layer combines linear state space models (SSMs), the HiPPO framework, and deep learning to achieve high performance. We build on the design of the S4 layer and introduce a new state space layer, the S5 layer. Whereas an S4 layer uses many independent single-input, single-output SSMs, the S5 layer uses one multi-input, multi-output SSM. We establish a connection between S5 and S4, and use this to develop the initialization and parameterization used by the S5 model. The result is a state space layer that can leverage efficient and widely implemented parallel scans, allowing S5 to match the computational efficiency of S4, while also achieving state-of-the-art performance on several long-range sequence modeling tasks. S5 averages 87.4% on the long range arena benchmark, and 98.5% on the most difficult Path-X task.
In Syntology Open this paper in Syntology's Atlas, the map of the papers in Syntology's graph and their citations.
For agents, Syntology's MCP tool lists every function and class Syntology harvested from this paper and whether it ran (how to connect): get_harvested_code_for_paper(arxiv_id="2208.04933")
Code
Syntology Ran 4 of 19 code samples harvested from 1 repository linked to this paper; 15 have no recorded run. Of those that ran: 1 ran · fixture could not drive it; 3 ran with no contract checked.
By repository: community (archive-listed): 16 samples from 1 repository, 3 ran; 3 identical to code first harvested elsewhere. The run record, sample by sample. “Ran” means executed on a synthesized input, not that the code is correct or reproduces the paper.
Repository list and official/mentioned flags are the archive's, frozen 2025-07-28. Reachability, where shown, is from one Syntology probe window (2026-09-16 to 2026-09-18); repositories not probed show nothing. GitHub stars are not tracked.
Code Syntology ran Syntology
19 samples harvested; 4 ran; 0 honoured the contract we drafted; 15 have no recorded run. Read from Syntology's graph 2026-09-24; that is when this build read the record, not when the samples ran.
Licence: 3 of the 19 samples are pointer only, meaning Syntology does not serve that copy's text. This page shows no code text for any sample; each one links to its file in the repository.
Harvested from leonty1/deepldnn. Some samples are identical code Syntology first harvested from another repository; for those, this paper's copy is not located and its licence is not recorded. “Ran” means the sample executed on a synthesized input. It does not mean the output is correct, and nothing here reproduces the paper's results. “Honoured” and “violated” refer to a contract Syntology drafted from the code itself; “our draft was wrong” and “fixture could not drive it” are failures of Syntology's instrument, not of the code.
Each sample ends with its code_sha256, Syntology's identity for that exact code. An agent fetches the stored sample with Syntology's MCP tool get_code(code_sha256="…") (how to connect); click an identity to copy that call.
Repository labels, per sample. official repository: The archive marks this repository official for the paper. named in the paper: The archive records that the paper mentions this repository; it is not marked official. community (archive-listed): In the archive's code links for this paper, not marked official and not recorded as mentioned in the paper. found in paper text by Syntology: Syntology found this repository in the paper's own text; whether it is the authors' implementation is not asserted. community: Not in the archive's code links for this paper; a community repository Syntology harvested. Samples from a repository marked official are listed first. Licence labels name the repository's licence as recorded at harvest. “Pointer only” means Syntology does not serve that copy's text, for one of four reasons: no licence file was found; the licence was not identified; the licence is recorded as permissive but that copy's record is not marked cleared; or the licence is outside the permissive list Syntology serves text under (MIT, Apache-2.0, BSD and similar). Some licences outside that list permit redistribution, such as WTFPL, and GPL-3.0 under its conditions; they are simply not on the list. Hover a licence label for the reason. File links open the file on GitHub at the default branch, which may have changed since the harvest.
ce310b19a858070f · report
1b76e4737067023f · report
1631cd936e9b1a90 · report
25c8f92b07a28373 · report
5db05fd542b84048 · report
72d464924b5dee96 · report
1bdd2b1087ff31b1 · report
b9da9054915aabbf · report
a06af5ba6942100d · report
037cf309e950d7ef · report
9d0777602eda354e · report
137297b83ef054cd · report
f8544563682146e5 · report
6f2f58700f9f2450 · report
6af6c9fb197b8e6b · report
3d3875d2fc5f4975 · report
b4fc72406d2ff673 · report
c0135e087b049ad1 · report
f9485e8e0d1e9aee · report
Tasks
2 archive task tags without a task page not shown.
Results from the paper archive 2025-07-28
| Task | Dataset | Model | Metric | Value | Rank at snapshot | Leaderboard | Report |
|---|---|---|---|---|---|---|---|
| Long-range modeling | LRA | S5 | Avg | 87.46 | #1 of 7 | Archive leaderboard | report |
| Long-range modeling | LRA | S5 | Image | 88 | #1 of 7 | Archive leaderboard | report |
| Long-range modeling | LRA | S5 | ListOps | 62.15 | #1 of 7 | Archive leaderboard | report |
| Long-range modeling | LRA | S5 | Pathfinder | 95.33 | #1 of 7 | Archive leaderboard | report |
| Long-range modeling | LRA | S5 | Pathfinder-X | 98.58 | #1 of 7 | Archive leaderboard | report |
| Long-range modeling | LRA | S5 | Retrieval | 91.4 | #1 of 7 | Archive leaderboard | report |
| Long-range modeling | LRA | S5 | Text | 89.31 | #1 of 7 | Archive leaderboard | report |
Ranks are positions in the archive's leaderboards as they stood at the 2025-07-28 snapshot. Results published since then are not among these rows, so a rank here is not a current standing.
Report a problem or propose a change · a person checks every report against the paper or source before anything changes; decisions are listed on /corrections