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webinar
webinars and virtual events
Zoom Webinars, Livestorm
System
Techniques · 32
Primitives · 97
webinar
CDN and edge
cloud · medium: CDNs cache content in hundreds of PoPs near users, cutting latency and egress bills; edge compute runs small code there. Bandwidth price spreads 10x between providers.
›
Deterministic simulation testing
distributed · medium: Run the whole system in one thread under a seeded scheduler with simulated network, disk and clock, so every failure replays from its seed.
›
Presence tracking
distributed · medium: Heartbeats refresh per-connection TTLs; a user is online while any connection lives, with a grace period that hides reconnect flaps.
›
Primary-backup replication
distributed · medium: One node orders all writes and ships them to standbys; the acknowledgement rule (none, one, all) sets what a crash loses, and an external arbiter decides who takes over.
›
Pub/sub fan-out
distributed · medium: Deliver one published message to every subscriber of a topic by sharing one encoded payload and giving each connection a bounded queue with an explicit slow-consumer policy.
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RNN transducer (RNN-T)
machine-learning · medium: Streaming sequence model that sums all monotone alignments in a frame-by-label lattice and conditions each label on earlier ones.
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Adaptive bitrate streaming
media · medium: The client fetches short HTTP segments and picks each segment's rendition from throughput estimates, buffer level, or both, trading stalls against quality and switches.
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Media containers
media · low: MP4/ISO BMFF, fragmented MP4/CMAF, Matroska and MPEG-TS mux/demux
RTP and RTCP
media · low: RTP stamps each media packet with sequence number, media-clock timestamp and source ID; RTCP reports loss, jitter, round trip and clock mapping within a bandwidth cap.
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Video codecs
media · low: H.264/HEVC/AV1 basics: frames, GOPs, hardware decode/encode APIs and latency settings
Hdr histogram
data-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentiles
HyperLogLog
data-structures · low: Counts distinct elements in kilobytes with about 1 % error by tracking the longest run of leading zero bits in hashed values per bucket.
›
Process supervision
hardware-os · low: A parent process starts services, reaps their exits and restarts them under a delay and burst-limit policy, then stops them with SIGTERM before SIGKILL.
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Opus codec
media · low: Opus audio codec: SILK/CELT modes, frame sizes, bitrate and FEC settings for real-time voice
Subtitle formats webvtt
media · low: WebVTT/SRT cues, timing and line-breaking rules
Open and click tracking
networking · low: Tracking pixels and signed redirect links for engagement events
WebSockets
networking · low: Full-duplex message framing over one upgraded HTTP connection; the standard way to push real-time data to browsers.
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Mutual TLS
security · low: TLS where the client also proves a certificate key, so every connection carries a verified, rotatable machine identity.
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Icalendar format
storage · low: ICalendar (RFC 5545) objects, VTIMEZONE and iTIP scheduling messages
Graceful draining
systems · low: On a termination signal, stop taking new work, finish in-flight work until a deadline, tell clients to reconnect elsewhere, then exit; clients resume from a token.
›
HTTP caching semantics
networking · low: The rules (RFC 9111) that decide whether a stored response is still fresh, and how a cheap conditional request revalidates it when it is not.
›
Cooperative scheduling
concurrency · low: Green threads/coroutines yielding at await points on a user-space scheduler
Record replay
distributed · low: Record every nondeterministic input (time, randomness, I/O, model and tool outputs, per-tick player input) and re-execute deterministically for debugging, replays and state rebuild
+ 25 more techniques
+ 81 more primitives
System
Techniques · 32
Primitives · 97
webinar
CDN and edge
cloud · medium: CDNs cache content in hundreds of PoPs near users, cutting latency and egress bills; edge compute runs small code there. Bandwidth price spreads 10x between providers.
›
Deterministic simulation testing
distributed · medium: Run the whole system in one thread under a seeded scheduler with simulated network, disk and clock, so every failure replays from its seed.
›
Presence tracking
distributed · medium: Heartbeats refresh per-connection TTLs; a user is online while any connection lives, with a grace period that hides reconnect flaps.
›
Primary-backup replication
distributed · medium: One node orders all writes and ships them to standbys; the acknowledgement rule (none, one, all) sets what a crash loses, and an external arbiter decides who takes over.
›
Pub/sub fan-out
distributed · medium: Deliver one published message to every subscriber of a topic by sharing one encoded payload and giving each connection a bounded queue with an explicit slow-consumer policy.
›
RNN transducer (RNN-T)
machine-learning · medium: Streaming sequence model that sums all monotone alignments in a frame-by-label lattice and conditions each label on earlier ones.
›
Adaptive bitrate streaming
media · medium: The client fetches short HTTP segments and picks each segment's rendition from throughput estimates, buffer level, or both, trading stalls against quality and switches.
›
Jitter buffer
media · medium: A receiver-side buffer holds packets just long enough, a delay tracked from recent arrivals, to reorder them and hand out media at a steady rate.
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Low latency hls dash
media · medium: Partial segments, chunked CMAF, blocking playlist reload for 2-5 s latency
Selective forwarding unit
media · medium: A server receives each participant's media once and forwards chosen packets to every other participant, picking the quality layer per receiver without decoding anything.
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Simulcast svc
media · medium: Simulcast and scalable video coding layers for per-receiver quality
Video transcoding ladder
media · medium: Turn one source into resolution x bitrate x codec renditions chosen from measured rate-quality points, cut on aligned keyframes so players can switch mid-stream.
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Webrtc
media · medium: WebRTC stack: ICE, DTLS-SRTP, RTP, congestion control and data channels for real-time media
Email delivery smtp
networking · medium: Outbound SMTP: queues, MX lookup, retries, bounces, feedback loops and IP warm-up
Coverage-guided fuzzing
security · medium: Mutate inputs, run an instrumented target, and keep any input that reaches a new code edge; feedback turns blind guessing into incremental search.
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Point-in-time recovery
storage · medium: Periodic base backups plus a continuously archived change log let you rebuild the state as of any instant, then branch from there.
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Autoscaling
systems · medium: Target-tracking scaler with stabilization windows, cooldowns and hysteresis
Delta debugging
compilers · medium: Ddmin minimization of failing inputs or change sets
Durable job queue
distributed · medium: Persisted tasks that workers lease for a visibility timeout, ack on success and retry with backoff; at-least-once execution that survives worker and queue crashes.
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Fault injection
distributed · medium: Inject latency, errors, kills and partitions via proxies, netem or hooks
Chunked parallel encoding
media · medium: Split video at keyframes, encode chunks in parallel, stitch with rate consistency
NAT traversal (STUN, ICE, TURN)
media · medium: Learn your public address with STUN, swap candidate addresses over signalling, test pairs with ICE checks, and fall back to a TURN relay if no direct path works.
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Packet loss concealment
media · medium: Synthesize missing audio frames from prior signal (pitch repetition, neural PLC)
Beam search decoding
ml-training · medium: Keep the k best partial sequences by summed log-probability at every step, set finished ones aside, and return the best (n-best) by a length-normalised score.
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Bounce processing
networking · medium: Parse DSNs and feedback loops, classify hard/soft bounces, maintain suppression lists
Delay based congestion control
networking · medium: One-way delay gradient estimation for real-time media (GCC, transport-cc)
TLS 1.3
security · medium: The standard encrypted, authenticated transport; one round trip, only forward-secret AEAD suites, and little left to misconfigure.
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ARIES recovery
storage · medium: Three-pass crash recovery (analysis, redo, undo) for steal/no-force buffer pools; repeats history, then rolls back losers with compensation log records.
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Video rate control
media · medium: CBR/VBR/CRF rate control with VBV buffer model and lookahead
Linear-time regular expression matc…
search-sort · medium: Match a regular expression in O(pattern x text) worst case by tracking all live parse positions at once, then cache the state sets as a lazily built DFA for speed.
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Syscall interception
security · medium: Intercept syscalls via ptrace, seccomp user notify or a user-space kernel
Buffer pool
storage · medium: The database's own page cache (frames, page table, pin counts, dirty bits, replacement) so it, not the OS, controls eviction, write order and I/O.
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Media containers
media · low: MP4/ISO BMFF, fragmented MP4/CMAF, Matroska and MPEG-TS mux/demux
RTP and RTCP
media · low: RTP stamps each media packet with sequence number, media-clock timestamp and source ID; RTCP reports loss, jitter, round trip and clock mapping within a bandwidth cap.
›
Video codecs
media · low: H.264/HEVC/AV1 basics: frames, GOPs, hardware decode/encode APIs and latency settings
Hdr histogram
data-structures · low: Log-linear bucketed histograms with bounded relative error for latency percentiles
HyperLogLog
data-structures · low: Counts distinct elements in kilobytes with about 1 % error by tracking the longest run of leading zero bits in hashed values per bucket.
›
Process supervision
hardware-os · low: A parent process starts services, reaps their exits and restarts them under a delay and burst-limit policy, then stops them with SIGTERM before SIGKILL.
›
Opus codec
media · low: Opus audio codec: SILK/CELT modes, frame sizes, bitrate and FEC settings for real-time voice
Subtitle formats webvtt
media · low: WebVTT/SRT cues, timing and line-breaking rules
Open and click tracking
networking · low: Tracking pixels and signed redirect links for engagement events
WebSockets
networking · low: Full-duplex message framing over one upgraded HTTP connection; the standard way to push real-time data to browsers.
›
Mutual TLS
security · low: TLS where the client also proves a certificate key, so every connection carries a verified, rotatable machine identity.
›
Icalendar format
storage · low: ICalendar (RFC 5545) objects, VTIMEZONE and iTIP scheduling messages
Graceful draining
systems · low: On a termination signal, stop taking new work, finish in-flight work until a deadline, tell clients to reconnect elsewhere, then exit; clients resume from a token.
›
HTTP caching semantics
networking · low: The rules (RFC 9111) that decide whether a stored response is still fresh, and how a cheap conditional request revalidates it when it is not.
›
Cooperative scheduling
concurrency · low: Green threads/coroutines yielding at await points on a user-space scheduler
Record replay
distributed · low: Record every nondeterministic input (time, randomness, I/O, model and tool outputs, per-tick player input) and re-execute deterministically for debugging, replays and state rebuild
PRNGs (PCG, xoshiro)
numerics · low: Small, fast, statistically strong non-cryptographic generators: PCG32 and xoshiro256**, with seeding, parallel streams and unbiased ranges.
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Hierarchical timing wheel
systems · low: Timers bucketed by expiry into wheels of slots, coarser wheels for far deadlines: O(1) insert and cancel for millions of timeouts.
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Leases
distributed · low: A lock that expires on its own: bounded-time ownership that survives crashes and partitions, given bounded clock drift and fencing tokens on writes.
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Write-ahead log
storage · low: Append each change to a checksummed sequential log and fsync it before touching data pages; the basis of crash durability in nearly every database.
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Health checking
systems · low: Decide per backend whether to route to it using probes and real-traffic errors, with consecutive-count hysteresis, capped ejection and a panic fallback.
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SPSC ring buffer
data-structures · low: Bounded wait-free queue for exactly one producer and one consumer thread, built from an array and two indices with acquire/release ordering.
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Topic matching trie
data-structures · low: Trie over topic levels with + and # wildcards for subscription matching
Backpressure
systems · low: Bound every queue and make a full queue push back on the producer by blocking, dropping, rejecting or withholding credit.
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Recurrent networks
machine-learning · low: GRU and LSTM cells for streaming sequence models
Short-time Fourier transform and sp…
signal-processing · low: Slide a window over a signal and FFT each frame to get a time-frequency picture; the front end of audio ML, vibration and radar analysis.
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Adaptive streaming manifests
media · low: HLS playlists and DASH MPDs: renditions, segment timelines, codecs strings
GOP structure
media · low: How an encoder orders I, P and B frames into groups of pictures: the knob behind seekability, compression, latency and stream switching.
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HTTP range requests
networking · low: Ask for byte offsets with Range and get a 206 slice back; the standard way to resume, seek and read big remote files piecewise.
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Exponential smoothing (ETS, Holt-Wi…
statistics · low: Forecast by keeping a few running states (level, trend, seasonal) updated by a fraction of each forecast error; O(1) memory per series and a strong baseline.
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A/V sync and media clocks
media · low: How audio and video stay lip-synced: per-stream timebases, PTS/DTS, PCR and RTCP clock mapping, and a master clock that slave streams chase by dropping, repeating or resampling.
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HTTP/2
networking · low: Binary multiplexed framing for HTTP over one TCP connection: streams, per-stream and per-connection credit windows, HPACK header compression and the limits that contain abuse.
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Long polling
networking · low: The client asks "anything after cursor X?"; the server holds the request until there is news or a timeout, and the client immediately asks again.
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Sdp offer answer
media · low: SDP session descriptions and offer/answer negotiation
SRTP
media · low: Per-packet encryption, authentication and replay protection for RTP and RTCP that keeps the headers readable, with the packet index derived from the 16-bit sequence number.
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Image resampling filters
graphics · low: Resize an image by convolving with a kernel (box, triangle, cubic, Lanczos) whose width scales with the shrink factor, done as two separable 1-D passes with precomputed weights.
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Perceptual quality metrics (PSNR, S…
media · low: Full-reference scores that say how bad a compressed picture looks: PSNR (pixel error), SSIM (structure), VMAF (learned fusion), and when each one lies.
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Sctp protocol
networking · low: SCTP multi-streaming, multi-homing and message framing for telecom signalling
SPF, DKIM and DMARC sender authenti…
networking · low: SPF authorizes sending IPs, DKIM signs the message, DMARC requires either to match the visible From domain and says what to do on failure.
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DNS message format and client looku…
networking · low: Binary query/response format of DNS (RFC 1035) and how a stub client uses it: record types, name compression, UDP/TCP/EDNS sizes, TTL caching.
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Smtp protocol
networking · low: SMTP/ESMTP sessions, pipelining, STARTTLS and reply codes
Exponential backoff with jitter
systems · low: Retry after delays that grow geometrically and are randomized, so failed clients spread out instead of hammering a recovering service in synchronized waves.
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Token bucket
systems · low: A bucket of up to b tokens refilled at rate r; requests spend tokens, enforcing an average rate while allowing bursts of b.
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Code coverage instrumentation
compilers · low: Insert counters into compiled code to record which blocks, edges or lines ran; a spanning tree of the control-flow graph cuts the counters needed.
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Fast hash functions
data-structures · low: Non-cryptographic hashes built from 64×64→128-bit multiplies and xor-shifts; pick by key size, trust level and whether the hash is persisted.
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Sanitizers
security · low: ASan/UBSan/TSan shadow memory and instrumentation to catch memory bugs
Object storage
cloud · low: S3-compatible blob storage at cents per GB-month with 11 nines durability; pick by egress price, request price and latency, not by storage price alone.
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Copy on write snapshots
storage · low: Point-in-time snapshots by sharing pages/extents and copying only on write
PID controller
robotics · low: Drive a measured value to a setpoint with three terms on the error: proportional, integral, derivative. The default feedback loop for motors, heaters, drones and gimbals.
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Sliding-window counters
systems · low: Count events in the last W seconds with a ring of sub-bucket counters; the two-bucket weighted estimate gives rate limits in 16 bytes per key.
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Failure bisection
search-sort · low: Binary search over commits, batches or inputs to isolate a failure
Dead-letter queue
distributed · low: A side queue for messages that keep failing: after N delivery attempts or a permanent error, park them with the reason so the main queue keeps moving.
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Idempotency keys
finance · low: 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.
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Transparent interception
networking · low: Redirect traffic to a local proxy (iptables TPROXY/REDIRECT, eBPF) without app changes
Scene cut detection
media · low: Detect shot changes from frame-difference statistics
Network address translation
networking · low: NAT mapping tables, endpoint-independent mapping/filtering, hairpinning and port allocation
Message authentication codes (HMAC,…
security · low: A keyed short tag proving a message is unmodified and came from a key holder; pick HMAC, CMAC, KMAC or a one-time polynomial MAC by what primitive you already have.
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Linear predictive coding (LPC)
media · low: Predict each sample from the previous p; code only the small prediction error plus p coefficients. Core of FLAC, speech codecs and the Opus SILK layer.
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d-ary heap
data-structures · low: Array heap with d children per node (d = 4 typical): half the binary heap's depth, siblings in one cache line, faster priority queues.
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Top-k selection
search-sort · low: Keep the k best of n items without sorting all n - bounded min-heap for streams, quickselect for arrays, threshold pruning to skip most items.
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Mime parsing
storage · low: RFC 5322/2045 headers, multipart bodies and transfer encodings
Kalman filter
robotics · low: Optimal recursive estimator for a linear system with Gaussian noise: fuses a motion model with noisy measurements into a state estimate plus its covariance.
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AEAD (AES-GCM, ChaCha20-Poly1305)
security · low: Authenticated encryption that encrypts and detects tampering in one call; the only kind of symmetric encryption you should use.
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Cryptographic hashes (SHA-2, BLAKE3)
security · low: Collision-resistant fingerprints of data; SHA-256 for interoperability, BLAKE3 for speed, HMAC/HKDF for keyed uses.
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ECDH key exchange (X25519, P-256)
security · low: Each side multiplies the other's public curve point by its own scalar and both get the same point; always validate the peer key and run the result through a KDF.
›
HKDF key derivation (extract-and-ex…
security · low: HMAC-based two-step key derivation: extract a uniform pseudorandom key from any secret, then expand it into as many context-bound keys as you need.
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X509 certificates
security · low: Certificate chains, path validation, SANs, revocation and short-lived issuance
Adaptive quantization
media · low: Per-block QP offsets driven by local texture energy: spend bits on flat areas where blocking shows, save them where texture masks the error.
›
Recursive-descent parsing
compilers · low: Hand-written top-down parser with one function per grammar rule; simple, fast, with full control over error messages and recovery.
›
Aho-Corasick multi-pattern matching
search-sort · low: Find all occurrences of many fixed patterns in one pass over the text, in time independent of the pattern count, using a trie with failure links.
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SIMD substring search
search-sort · low: Find bytes or substrings by comparing 16-64 haystack positions per instruction against the needle's first and last byte, then verifying the rare candidates.
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LRU and CLOCK
systems · low: LRU evicts the least recently used entry via hash map plus linked list; CLOCK approximates it with a reference bit, so hits take no lock.
›
Ebpf
hardware-os · low: Verified in-kernel programs on hooks (kprobes, XDP, tc) with maps
Ptrace process control
hardware-os · low: Ptrace: attach, read and write registers and memory, single-step, intercept signals
Seccomp bpf
security · low: Syscall filtering with seccomp BPF programs
fsync, O_DSYNC and O_DIRECT
hardware-os · low: 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.
›
S3-FIFO
systems · low: Three FIFO queues (small, main, ghost) that evict one-hit wonders quickly and keep reused objects; low miss ratios with no list moves on hits.
›
Control-flow graph
compilers · low: Split a linear instruction list into basic blocks and connect them by jumps; the graph every optimizer, SSA builder and dataflow pass walks.
›
False sharing
concurrency · low: Independent variables written by different cores on one cache line force the line to bounce between cores; pad or regroup hot data to fix it.
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Memory ordering
concurrency · low: What Relaxed, Acquire, Release and SeqCst atomics actually guarantee, what they cost on x86 and ARM, and which one each pattern needs.
›
Fencing tokens
distributed · low: 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.
›
Convolution image filters
graphics · low: Separable 2D convolution kernels for blur, sharpen (unsharp mask) and edges with border handling
BFS and DFS
graphs · low: The two basic graph traversals; BFS gives hop distances and levels, DFS gives discovery/finish order for cycles, components and topological order.
›
Minimum spanning tree
graphs · low: Cheapest set of edges connecting all vertices; Kruskal sorts edges and joins components with union-find, Prim grows one tree, Boruvka merges in parallel rounds.
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Union-find
graphs · low: Disjoint-set forest with union by size and path compression; merges sets and answers same-set queries in effectively constant time.
›
CPU caches and the memory hierarchy
hardware-os · low: Sizes, line widths and latencies of L1/L2/L3/DRAM on modern x86 and Apple M-series, and the data-layout rules that follow from them.
›
CRC32C checksums
hardware-os · low: 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.
›
SIMD programming
hardware-os · low: Process 4-16 lanes per instruction with AVX2, AVX-512 or NEON via Rust std::arch, with runtime dispatch and a portable fallback.
›
Discrete cosine transform
numerics · low: Fast integer DCT/DST block transforms used by image and video codecs
Fast Fourier transform
numerics · low: Computes the DFT in O(n log n) by recursively splitting into even and odd halves; the basis of fast convolution and spectral methods.
›
Sparse matrices (CSR)
numerics · low: Compressed sparse row stores only nonzeros as row pointers, column indices and values; SpMV streams them once, so it is memory-bandwidth bound.
›
Scalar quantization
search-sort · low: Per-dimension int8/binary quantization of vectors with rescoring
Constant time code
security · low: Writing secret-dependent code without branches or memory lookups on secrets; constant-time compare and select
Csprng
security · low: OS-backed cryptographically secure random numbers (getrandom), and when a fast PRNG is not enough
Biquad filters
signal-processing · low: Second-order IIR sections (RBJ cookbook): low/high pass, peaking EQ; stable cascades
IIR and FIR filters
signal-processing · low: Two ways to shape a sampled signal's spectrum: FIR (finite taps, always stable, exact linear phase) or IIR (feedback, a few coefficients, cheap but phase-distorting).
›
Slab allocator
systems · low: Pre-carve pages into equal-size slots per size class with an in-place free list: O(1) alloc and free, no external fragmentation, cache-warm reuse.
›
Copy for AI
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