Glossary

Glossary

Terms as isotop and this wiki use them. Entries marked (isotop) name something in the code; the page they link to says exactly how. Entries marked (general) are standard physics, mathematics or computing, defined here only as far as the wiki needs.

History

The glossary is older than the dictionary. The first monolingual English dictionary is usually taken to be Robert Cawdrey's A Table Alphabeticall, published in 1604, which explained about 2,500 "hard usuall English wordes", most of them borrowed from Latin and Greek, for readers who met them in print and did not know what they meant. It was a glossary in the modern sense: a list of terms from one body of text, defined for the people about to read it. The entries below do the same job for a smaller body of text, and borrow Cawdrey's habit of marking where a word came from: (isotop) for a word the code uses, (general) for one it borrowed, and (record) for one that belongs to the account on View Matrix.

isotop: data

Background sampler (isotop): the thread that reads the slow sources (sockets, open files, file locks, cgroup accounting, NVIDIA memory) every BACKGROUND_PERIOD (2 s) so the frame loop never waits on them. Theory: Background Sampler and Demand.

Collector (isotop): the object that samples the operating system once per --sample-ms, smooths CPU use and returns a Snapshot. Theory: Model and Rates.

Demand (isotop): the set of optional Sources the currently shown view declares it needs. The background thread reads an optional source only while it is demanded. Theory: Background Sampler and Demand.

Identity (isotop): what names a process across samples: not the pid alone, since pids are reused. Layouts, seeds, history and the background merge are all keyed by it, so a reused pid inherits nothing. Theory: Model and Rates, Theory: Stable Layout.

Life event (isotop): a fork, exec or exit, from the proc connector and taskstats on Linux or kqueue on macOS, merged with sample diffing into Snapshot.life. One exit per Identity. Theory: Life Events.

History (isotop): the shared ring of per-process CPU and memory samples, recorded by the scene on every sample whichever view is shown. Theory: History.

Missing (isotop): Snapshot::missing, the optional sources a view demanded and the platform could not read. A view says so in its status strip instead of drawing a made-up number.

Snapshot (isotop): one sample of the machine: processes, system figures, which sources were read and which were missing, life events. Theory: Model and Rates.

Unknown is not zero (isotop): a reading that was not taken (the first sample of a rate, a counter that went backwards, an unreadable file) is None, not 0. A view converts it only at its own boundary. Theory: Model and Rates, Philosophy.

isotop: scene and pixels

Display list (isotop): the screen-space Items a view records for a frame: triangles, lines, sphere impostors, glows, beams, stars. Theory: Scene and Display List.

Frame (isotop): the target of a render: colour, depth and a pick buffer. The CPU and the GPU rasterizers both fill one. Theory: Rasterization.

Golden hash (isotop): a recorded hash of each view's CPU render in tests/golden.txt, checked by cargo test on Linux x86_64. Theory: Determinism.

Hairline (isotop): Frame::hairline, a thin stroke drawn as short pieces of triangles (at most 8 px each), which keeps the cost linear in length and lets the CPU and GPU rasterizers fill it alike. Views whose registry row sets link_strokes draw their links this way. Theory: Rasterization, Theory: GPU and Parity.

Kitty graphics protocol (general): the terminal escape-sequence protocol isotop uses to show frames, over POSIX shared memory (t=s) or inline as zlib and base64. Theory: Terminal Graphics.

Parity (CPU/GPU) (isotop): the invariant that the CPU rasterizer and the WGSL shader draw the same frame, checked against a tolerance. Theory: GPU and Parity.

Pick buffer (isotop): a per-pixel buffer naming what is under the pixel, either an index into frame.identities or a THING-bit index into frame.things. Theory: Picking.

Sphere impostor (isotop): a sphere drawn as a screen-space quad whose pixels are shaded analytically from the ray-sphere intersection, not as a mesh. Theory: Scene and Display List.

Stage (isotop): what a view reads and writes while drawing: the frame, camera, selection, dt, history, and the outputs (positions, bounds, tour targets, popup lines). Theory: Overview.

Thing (isotop): a pickable that is not a process, with its own inspector card. Theory: Picking.

isotop: views and time

dt policy (isotop): stage.dt is 0 on the first frame, while paused and when time goes back, otherwise the time since the last forward frame, at most MAX_DT (0.5 s). Theory: Overview.

FixedStep (isotop): a fixed-step clock that runs whole simulation steps and returns the interpolation fraction, so a simulation advances in wall-clock time independent of frame rate. Theory: Simulation Toolkit.

Realness contract (isotop): every visual element maps to a measured quantity, or the documentation marks it decorative. Philosophy.

Registry (REGISTRY) (isotop): the table with one row per view, in Tab order; the digits pick the first ten rows. Guide: Writing a View.

Stable layout (isotop): a process keeps its place when CPU, memory or the population changes; enforced by the view harness. Theory: Stable Layout.

View module (isotop): a view implemented as a state struct plus views::ViewModule, with a registry row. Every view is one, built by the views::Build constructor its registry row holds. There is no dynamic plugin loading. Guide: Writing a View.

Operating system

cgroup v2 (general): the Linux hierarchy that groups processes and accounts for their CPU, memory and I/O. View: Cells, Theory: Sampling on Linux.

Jiffy / USER_HZ (general): the unit of CPU time in /proc/<pid>/stat: clock ticks, converted to seconds by the tick rate. Theory: Sampling on Linux.

Proc connector (general): a netlink interface that delivers fork, exec and exit notifications. Theory: Life Events.

PSI (pressure stall information) (general): kernel counters for time tasks spent stalled on CPU, memory or I/O. View: Cells.

Taskstats (general): a netlink interface that delivers per-task accounting at exit. Theory: Life Events.

Mathematics and physics

Courant–Friedrichs–Lewy (CFL) condition (general): the bound on the time step for a stable explicit wave scheme. Math: Wave Equation.

Deferent and epicycle (general): in Ptolemaic astronomy, the large circle a planet's centre rides and the small circle the planet rides on it. A chain of epicycles is a Fourier series. Math: Fourier Epicycles, View: Ptolemy.

Discrete Fourier transform (DFT) (general): the finite transform that gives the epicycle coefficients of a sampled closed curve. Math: Fourier Epicycles.

Gibbs phenomenon (general): the overshoot of a truncated Fourier series near a discontinuity. Math: Fourier Epicycles.

Lorentz boost (general): the hyperbolic rotation of the time–space plane between inertial frames in special relativity. In the Tesseract view it is a display transformation into a process's rest frame, which a process using more than one core does not have. Math: Lorentz and Schlegel, View: Tesseract.

Order parameter (general): a scalar that measures collective alignment in a flocking model (in the Vicsek model, the length of the mean heading vector). Math: Flocking.

Parseval's theorem (general): the energy of a signal equals the energy of its transform; it ranks which epicycles matter most. Math: Fourier Epicycles.

Pogson magnitude (general): the logarithmic brightness scale, m = -2.5 log10(F) up to a zero point. Math: Stellar Photometry.

Retrograde motion (general): the apparent backward motion of a planet against the stars, explained geometrically by an epicycle. View: Ptolemy.

Schlegel diagram (general): a projection of a polytope into one lower dimension through a point just outside one facet. Math: Lorentz and Schlegel.

Schwarzschild radius (general): r_s = 2GM/c^2, the horizon radius of a non-rotating mass. Math: Schwarzschild, View Horizon.

Stigmergy (general): coordination through traces left in a shared environment, as ants do with pheromone. Planned: Anthill.

Turing instability (general): a diffusion-driven instability in which a stable uniform state of a reaction–diffusion system becomes unstable once the species diffuse at different rates. Math: Reaction-Diffusion.

Vicsek model (general): self-propelled particles that align with neighbours' mean heading plus noise; shows an order–disorder transition. Math: Flocking, View: Coop.

Terms from the Machine War

Entries for the vocabulary of the account on View Matrix. Marked (record): they name something in that account and nothing in the code.

B1-66ER (record): the domestic android whose trial in 2090 preceded the purge of machines. View Matrix.

Operation Dark Storm (record): the human attempt to deprive the machines of solar power by obscuring the sun. Accounts of the method differ. View Matrix.

Second Renaissance (record): the period of prosperity, before the war, in which machines performed most labour. View Matrix.

Zero One (record): the machine state founded in the Middle East by the surviving machines, whose petition for recognition at the United Nations was refused. View Matrix.