Algorithm

Single-Instruction Multiple-Data parallelism on x86 — the SSE/AVX/AVX-512 register sets and instruction families, when SIMD pays off, autovectorization vs intrinsics vs portable wrappers (`std::experimental::simd`, Highway, xsimd), and the gotchas (alignment, tail handling, downclocking on AVX-512).

Matchings in bipartite graphs — definitions (maximum matching, perfect matching, maximum-weight matching), Hopcroft-Karp for unweighted bipartite max matching in O(E√V), the Hungarian algorithm for weighted assignment, König's theorem connecting matching and vertex cover, and Hall's marriage theorem.

Mathematical methods for combining a dynamical model's forecast with observations to produce a best-estimate trajectory — sequential (Kalman filter family, ensemble Kalman filter, particle filter) vs variational (3D-Var, 4D-Var). Widely used in weather forecasting, oceanography, reservoir engineering, and SLAM.