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ocean-model

ocean circulation model

MOM6, NEMO

Open the ocean-model pageocean-model Batch checkpoint restartdistributed: Large batch jobs (end-of-day, settlement, payroll runs) that checkpoint and restart idempotentlyHalo exchangedistributed: Each rank stores its block plus a border copy of its neighbours' edge cells, refreshed by small messages every step; communication scales with block surface, not volume.›Parallel file system stripingdistributed: Striping files across object storage targets (Lustre, GPFS); collective I/O and metadata serversRange partitioningdistributed: Cut the sorted key space into contiguous half-open ranges kept in a boundary map; split hot or big ranges, merge small ones, move ranges between nodes.›CUDA and GPU languageslanguages: Programming GPUs: thousands of lockstep threads, bound by memory bandwidth; libraries first, Triton for fused kernels, CUDA C++ for peak speed.›Collective communicationml-training: The family of group exchanges (broadcast, reduce, all-gather, reduce-scatter, all-to-all) and the latency-plus-bytes cost model that picks ring, tree or direct algorithms by message size and topology.›Conjugate gradientnumerics: Krylov iteration for symmetric positive definite Ax = b using one matrix-vector product and two dot products per step; converges in about √κ iterations.›Conservative regriddingnumerics: Remap fields between grids preserving integrals, using overlap areas (first and second order)Data assimilation 4dvarnumerics: Fit model initial state to observations by minimizing a cost over a time window with adjoint gradientsFinite volume methodnumerics: Conservative cell-averaged discretization with numerical fluxes on structured and unstructured meshesFlux limiters upwindingnumerics: Upwind schemes, TVD flux limiters, MUSCL and Riemann solvers for shock-capturing advectionReproducible reductionnumerics: Order-independent floating-point sums (fixed order, Kahan, binned) for bit-for-bit reproducibilitySpherical gridsnumerics: Lat-lon, cubed-sphere and icosahedral grids for global models; pole and area issuesVerlet / leapfrognumerics: Half-kick, drift, half-kick: a second-order, time-reversible, symplectic integrator with one force evaluation per step whose energy error stays bounded for millions of steps.›Chunked array storagestorage: Cut an N-dimensional array into a regular grid of independently compressed blocks, so a slice read touches only the overlapping blocks and writers to different blocks run in parallel.›Idempotency keysfinance: Client-chosen unique key per logical operation, stored with a request fingerprint and the final response, so retries replay the first result instead of acting twice.›Write-ahead logstorage: Append each change to a checksummed sequential log and fsync it before touching data pages; the basis of crash durability in nearly every database.›Cron schedulingsystems: Cron expression parsing and next-fire-time computation, with catch-up and time-zone rulesEager rendezvous protocoldistributed: MPI point-to-point: eager sends for small messages, rendezvous handshake for large onesZero-copy I/Onetworking: Move bytes between files, sockets and NICs by passing page references instead of copying through user space: sendfile, splice, MSG_ZEROCOPY, kTLS.›Rdmanetworking: RDMA verbs over InfiniBand/RoCE: queue pairs, memory registration, one-sided opsLeasesdistributed: A lock that expires on its own: bounded-time ownership that survives crashes and partitions, given bounded clock drift and fencing tokens on writes.›Polygon clippinggeometry: Polygon intersection/union/difference (Weiler-Atherton, Martinez) for spatial predicatesR-treegeometry: A balanced tree of nested bounding boxes that indexes rectangles and points, answering window and nearest-neighbour queries by pruning whole subtrees.›Reverse-mode automaticdifferentiationml-training: Record the forward computation on a tape, then sweep it backwards once to get the gradient of a scalar loss for all inputs.›L-BFGSnumerics: Quasi-Newton minimizer that approximates the inverse Hessian from the last m gradient differences via the two-loop recursion; O(m·n) memory and work per step.›Sparse matrices (CSR)numerics: Compressed sparse row stores only nonzeros as row pointers, column indices and values; SpMV streams them once, so it is memory-bandwidth bound.›+ 7 moreCryptographic hashes (SHA-2,BLAKE3)security: Collision-resistant fingerprints of data; SHA-256 for interoperability, BLAKE3 for speed, HMAC/HKDF for keyed uses.›Exponential backoff with jittersystems: Retry after delays that grow geometrically and are randomized, so failed clients spread out instead of hammering a recovering service in synchronized waves.›CRC32C checksumshardware-os: The Castagnoli CRC-32 with dedicated instructions on x86 (SSE4.2) and ARMv8. It is the standard fast integrity check for storage blocks, logs and network frames.›fsync, O_DSYNC and O_DIRECThardware-os: What fsync, fdatasync, O_DSYNC, O_DIRECT and F_FULLFSYNC really guarantee on Linux and macOS, and the exact call sequences for crash-safe files.›Fencing tokensdistributed: A number that grows with every lock grant and is checked by the protected resource, so a paused ex-holder's late write is rejected.›d-ary heapdata-structures: Array heap with d children per node (d = 4 typical): half the binary heap's depth, siblings in one cache line, faster priority queues.›Exact geometric predicatesgeometry: Robust orient and incircle tests with adaptive-precision floats (Shewchuk) or exact arithmeticPoint in polygongeometry: Ray-casting/winding tests and indexed polygon lookup for reverse geocoding+ 4 morePRNGs (PCG, xoshiro)numerics: Small, fast, statistically strong non-cryptographic generators: PCG32 and xoshiro256**, with seeding, parallel streams and unbiased ranges.›SIMD programminghardware-os: Process 4-16 lanes per instruction with AVX2, AVX-512 or NEON via Rust std::arch, with runtime dispatch and a portable fallback.›

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