{"state_type":"pith_open_graph_state","state_version":"1.0","pith_number":"pith:2024:MVB4AXDA6FL5CRPSUVP6S7RXAF","merge_version":"pith-open-graph-merge-v1","event_count":2,"valid_event_count":2,"invalid_event_count":0,"equivocation_count":0,"current":{"canonical_record":{"metadata":{"abstract_canon_sha256":"d6f9196ddb6922f4e83529fc163ae2385e3c6004fee1a91e18f865262af9ec43","cross_cats_sorted":["math.DS","physics.geo-ph"],"license":"http://creativecommons.org/licenses/by/4.0/","primary_cat":"cs.LG","submitted_at":"2024-08-05T18:36:13Z","title_canon_sha256":"93a0e68546b71a6f8d4582e2d3f6a41096321c67ebe7cef97cfb002a8f4b43f1"},"schema_version":"1.0","source":{"id":"2408.02767","kind":"arxiv","version":1}},"source_aliases":[{"alias_kind":"arxiv","alias_value":"2408.02767","created_at":"2026-07-05T08:52:39Z"},{"alias_kind":"arxiv_version","alias_value":"2408.02767v1","created_at":"2026-07-05T08:52:39Z"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.2408.02767","created_at":"2026-07-05T08:52:39Z"},{"alias_kind":"pith_short_12","alias_value":"MVB4AXDA6FL5","created_at":"2026-07-05T08:52:39Z"},{"alias_kind":"pith_short_16","alias_value":"MVB4AXDA6FL5CRPS","created_at":"2026-07-05T08:52:39Z"},{"alias_kind":"pith_short_8","alias_value":"MVB4AXDA","created_at":"2026-07-05T08:52:39Z"}],"graph_snapshots":[{"event_id":"sha256:d1d1b4520f6833be9fbcf6a0ea4d836f958e7e6b2cfddd3e5c3d78485ebdaada","target":"graph","created_at":"2026-07-05T08:52:39Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"graph_snapshot":{"author_claims":{"count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","strong_count":0},"builder_version":"pith-number-builder-2026-05-17-v1","claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"integrity":{"available":true,"clean":true,"detectors_run":[],"endpoint":"/pith/2408.02767/integrity.json","findings":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938","summary":{"advisory":0,"by_detector":{},"critical":0,"informational":0}},"paper":{"abstract_excerpt":"Constraining a numerical weather prediction (NWP) model with observations via 4D variational (4D-Var) data assimilation is often difficult to implement in practice due to the need to develop and maintain a software-based tangent linear model and adjoint model. One of the most common 4D-Var algorithms uses an incremental update procedure, which has been shown to be an approximation of the Gauss-Newton method. Here we demonstrate that when using a forecast model that supports automatic differentiation, an efficient and in some cases more accurate alternative approximation of the Gauss-Newton met","authors_text":"Kylen Solvik, Stephan Hoyer, Stephen G. Penny","cross_cats":["math.DS","physics.geo-ph"],"headline":"","license":"http://creativecommons.org/licenses/by/4.0/","primary_cat":"cs.LG","submitted_at":"2024-08-05T18:36:13Z","title":"4D-Var using Hessian approximation and backpropagation applied to automatically-differentiable numerical and machine learning models"},"references":{"count":0,"internal_anchors":0,"resolved_work":0,"sample":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2408.02767","kind":"arxiv","version":1},"verdict":{"created_at":null,"id":null,"model_set":{},"one_line_summary":"","pipeline_version":null,"pith_extraction_headline":"","strongest_claim":"","weakest_assumption":""}},"verdict_id":null}}],"author_attestations":[],"timestamp_anchors":[],"storage_attestations":[],"citation_signatures":[],"replication_records":[],"corrections":[],"mirror_hints":[],"record_created":{"event_id":"sha256:bbf8ba7ec4ef4f0d29ad1381e06bfdf3d2c2ae45002e35c6512229cb9dd96526","target":"record","created_at":"2026-07-05T08:52:39Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"attestation_state":"computed","canonical_record":{"metadata":{"abstract_canon_sha256":"d6f9196ddb6922f4e83529fc163ae2385e3c6004fee1a91e18f865262af9ec43","cross_cats_sorted":["math.DS","physics.geo-ph"],"license":"http://creativecommons.org/licenses/by/4.0/","primary_cat":"cs.LG","submitted_at":"2024-08-05T18:36:13Z","title_canon_sha256":"93a0e68546b71a6f8d4582e2d3f6a41096321c67ebe7cef97cfb002a8f4b43f1"},"schema_version":"1.0","source":{"id":"2408.02767","kind":"arxiv","version":1}},"canonical_sha256":"6543c05c60f157d145f2a55fe97e3701490dd4cc5c91ec3718c9e7587b57cd40","receipt":{"algorithm":"ed25519","builder_version":"pith-number-builder-2026-05-17-v1","canonical_sha256":"6543c05c60f157d145f2a55fe97e3701490dd4cc5c91ec3718c9e7587b57cd40","first_computed_at":"2026-07-05T08:52:39.780725Z","key_id":"pith-v1-2026-05","kind":"pith_receipt","last_reissued_at":"2026-07-05T08:52:39.780725Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","receipt_version":"0.3","signature_b64":"ksb0cMs2UcFlkQwX+x9b/fbcNu/rzBSyrXooPas+Qg6tr+NFryA2PZ6vXyPlUxwor7hBn2oCBUiECnILdGVxCw==","signature_status":"signed_v1","signed_at":"2026-07-05T08:52:39.781147Z","signed_message":"canonical_sha256_bytes"},"source_id":"2408.02767","source_kind":"arxiv","source_version":1}}},"equivocations":[],"invalid_events":[],"applied_event_ids":["sha256:bbf8ba7ec4ef4f0d29ad1381e06bfdf3d2c2ae45002e35c6512229cb9dd96526","sha256:d1d1b4520f6833be9fbcf6a0ea4d836f958e7e6b2cfddd3e5c3d78485ebdaada"],"state_sha256":"6451b369539f753bb34ffb790f4375fea171856c6913cf9ab6bd62e7e721b375"}