Blame README.md at d71391e85dda17eaca644db62751ebde4f742551 - concept-collection/turing-surface-cache

concept-collection / turing-surface-cache

4f822e1 turing-surface-cache: reaction-diffusion solutions at a chosen end time, shared through a cloud cacheJeremy Magland 9 days ago1# turing-surface-cache

3Reaction-diffusion systems (Turing patterns) on curved closed surfaces,

4evaluated at a chosen end time, with the solutions shared between all visitors

5through a cloud cache.

7This is a trimmed fork of

8[turing-surface](https://github.com/concept-collection/turing-surface), which

9solves the same systems live and freely tunable. What this app changes is the

10contract: every setting is a choice from a short list, so each combination of

11choices names exactly one solution. Solutions already in the shared cache load

12by themselves as the choices are browsed; a combination nobody has computed

13shows empty surfaces, and nothing runs until the user presses **Compute

14solution**, which runs the solver locally (in the browser, on WebGPU),

15watching the pattern form and stopping at exactly the requested time. Users

16who hold an upload API key contribute their locally-computed solutions back,

17so the next visitor who asks for the same combination gets it in a second

18rather than a minute.

20## The discrete parameter space

481eeb9 Add Brusselator and Allen-Cahn modelsJeremy Magland 8 days ago22Three models ship, all in turing-surface's 6-transform flux form —

23Schnakenberg (the default), Brusselator, and Allen–Cahn — on three geometries

24(sphere, ellipsoid, peanut). The Algorithm-4 reference variant is deliberately

25absent: it solves the same equations as Schnakenberg and would only duplicate

26cache entries under different hashes. The choices, defined in

4f822e1 turing-surface-cache: reaction-diffusion solutions at a chosen end time, shared through a cloud cacheJeremy Magland 9 days ago27[`src/cache/options.ts`](src/cache/options.ts):

29| setting | choices |

30|---|---|

481eeb9 Add Brusselator and Allen-Cahn modelsJeremy Magland 8 days ago31| Schnakenberg | a: 0.05/**0.1**/0.15/0.2 · b: 0.7/**0.9**/1.1/1.3 · D₁: 1.6e-4/**4e-4**/1e-3 · D₂: 3.2e-3/**8e-3**/2e-2 · dt: 0.02/**0.05**/0.1 |

32| Brusselator | A: 2/**3**/4 · B: 7/**9**/11 · D₁: 1.7e-3/**3.33e-3**/6.7e-3 · D₂: 8.3e-3/**1.67e-2**/3.3e-2 · dt: 0.01/**0.02**/0.05 |

33| Allen–Cahn | ε²: 5e-4/**1e-3**/2e-3 · dt: 0.01/**0.02**/0.05 |

4f822e1 turing-surface-cache: reaction-diffusion solutions at a chosen end time, shared through a cloud cacheJeremy Magland 9 days ago34| geometry | sphere, **ellipsoid** (axes each 0.6/1/1.5), peanut (waist 0.4/0.6/0.8, stretch 0/0.6/1.2) |

35| seed | **1**–5 |

36| end time | **100**, 200, 400, 800, 1600 |

481eeb9 Add Brusselator and Allen-Cahn modelsJeremy Magland 8 days ago38The model, unlike every other choice, is compiled into the GPU session, so

39switching it pays a recompile of a second or two; everything else swaps into

40the running session. Allen–Cahn evolves one species, so it shows one panel

41where the others show two.

4f822e1 turing-surface-cache: reaction-diffusion solutions at a chosen end time, shared through a cloud cacheJeremy Magland 9 days ago43(Defaults in bold.) The numerical-scheme settings are fixed — lmax 63, 8

44solve iterations, seed wavelength λ = 0.5 — but are recorded in every cache

45key, so offering them as choices later invalidates nothing.

47The whole selection is mirrored into the URL fragment, every value written

48explicitly, so reloading returns to the same combination and a shared link

49opens on the same spec (and, when cached, the same solution) for whoever

50follows it. A "Reset to defaults" button puts every choice back.

52Every end time is an exact multiple of every dt, so a run to T = 800 passes

53exactly through t = 100, 200 and 400. Those intermediate states are captured

54as the run passes them and, for an uploading user, encoded and uploaded in

55the background while the run continues: one long run populates four cache

56entries, and the earlier ones are already shared before the run finishes. The same structure works in the other

57direction: the state is Markovian in the spectral coefficients, so before

58computing anything the app looks for the longest cached shorter run of the

59same spec and continues from its final state, computing only the remainder.

60Asking for T = 1600 when T = 800 is cached costs half the run, and the t = 0

61initial state travels inside every file of the chain, so a continuation

62writes files identical in kind to a from-scratch run.

64## How the cache works

66The page's whole state is one small spec object (model, parameters, geometry,

67seed, end time, scheme settings, plus the app name and a format version). Its

68canonical JSON — keys sorted at every level — is hashed with SHA-256, and the

69hash is the object name:

71```

72https://tempory.net/tmpbucket/turing-surface-cache/v1/schnakenberg/<sha256>.h5

73```

75A lookup is therefore a single GET with no index or API, and a 404 means a

76miss. The path carries the app name, format version and model in the clear so

77that future cleanup (lifecycle rules, prefix deletes) never has to open a file

78to know what it belongs to; the hash input includes the version string, so a

79format change moves every object rather than silently colliding with the old

80ones.

1a1e473 Add auto-fill: work through the parameter space on an idle machineJeremy Magland 8 days ago82## Filling the cache

84A cache only pays off once it holds what people ask for, and nobody wants to

85sit through the first computation of every combination. **Auto-fill the

86cache** — offered only when an upload API key is present — turns an otherwise

87idle machine into a contributor: it works through the parameter space,

88skipping whatever is already cached and computing and uploading the rest, and

89runs until stopped.

91Two decisions make that practical. The first is the order. About 8,400

92combinations exist (228 model-parameter sets × 37 geometries, with the seed

93and dt pinned), which is roughly three GPU-weeks at this repo's ~180 steps/s —

94exhaustible in principle, but only if the useful part comes first. Since a

95visitor starts at the defaults and changes one dropdown at a time, the chance

96that a combination is ever requested falls off steeply with the number of

97knobs that differ from the defaults, so the walk proceeds by that distance:

98every one-knob deviation before any two-knob one. One machine overnight covers

99every one- and two-knob deviation from every model's defaults, which is most

100of what anyone will ever click; the long tail can take as long as it likes.

101

102The second is that within a distance the order is **random**, and that is the

103entire coordination mechanism. Several idle browsers walking the same tiers in

104different orders, each skipping what it finds already cached, rarely duplicate

105each other and need no coordinator, no work queue, and no knowledge of one

106another. A skip costs one `HEAD` request, so a machine joining a

107well-filled region catches up in seconds.

108

109The seed and dt are pinned rather than surveyed (seed 1, dt 0.05): a seed

110picks a draw and means nothing on its own, and dt is a numerical knob rather

111than a property of the problem, so surveying either would multiply the work

112without adding a solution anyone asked for. Both are the default of every

113model, so an auto-filled entry is exactly what a visitor arriving at the

114defaults requests. Two smaller points: the walk skips the ellipsoid with all

115axes 1, since that *is* the unit sphere and the sphere geometry already

116covers it, and any run whose state goes non-finite is reported and discarded

117rather than uploaded — an unattended walk must not publish wreckage under a

118hash someone later trusts.

119

120Because it is meant to run unattended, the compute loop never waits on an

121animation frame and skips rendering entirely while the page is hidden, so a

122minimized window or a background tab keeps computing at full speed rather

123than being throttled to a crawl.

124

4f822e1 turing-surface-cache: reaction-diffusion solutions at a chosen end time, shared through a cloud cacheJeremy Magland 9 days ago125Uploads go through the [tmpbucket](https://github.com/scratchrealm/tmpbucket)

126Worker: the client presents the API key and a file name, receives a presigned

127R2 PUT URL, and uploads directly. Only holders of the key can write; everyone

128can read. The key is entered in the page and kept in localStorage.

129

c2317d0 Fill the cache from the command line, without a browserJeremy Magland 8 days ago130## Filling it from the command line

131

132A browser window is a poor place to leave a long computation, so the same walk

133runs outside one:

134

135```

136TURING_SURFACE_CACHE_KEY=… npx https://concept-collection.github.io/turing-surface-cache/fill.tgz

137```

138

139Nothing is published to the npm registry — npm installs a tarball from a URL

140as happily as from a package name, and the tarball is built and deployed

141beside the page, so the command line is always the same commit as the app.

142The page itself offers this command, ready to copy, once an upload key is

b32cc02 Offer the fill command in the page, ready to copyJeremy Magland 8 days ago143entered; the key is masked in what the page shows and real in what it copies,

144so that pasting it onto a fresh machine takes one step while a screenshot of

145the page still gives nothing away. The key can also be saved for later runs

146(`login` prompts for it and

c2317d0 Fill the cache from the command line, without a browserJeremy Magland 8 days ago147writes `~/.config/turing-surface-cache/key`), or passed as `--key`, though the

148environment is preferable: a key on the command line is visible to every user

149on the machine through `ps`, while another process's environment is not.

150

d3fa654 Say what is wrong when node is too old, and run on node 18Jeremy Magland 8 days ago151Node 18 or newer is required — the cache keys are SHA-256 through WebCrypto,

152which older node does not have as a global, and node 18 itself has it only

153under `node:crypto`, which is worth supporting since that is what several

154current distributions ship. An older node than that cannot even parse the

155bundle, and would otherwise report a syntax error pointing at a brace, so the

156published command is a small ES5 launcher that checks the version first and

157says what to do about it.

158

b0546a9 Fix the command line's file writing, and how it gets updatedJeremy Magland 8 days ago159One consequence of installing from a URL is worth knowing. npx keys its

160install directory on the whole spec string it was given, so a URL that never

161changes keeps running whatever it first installed, however often the file

162behind it has been replaced — and neither `--prefer-online` nor a changed

163version in the manifest makes any difference, since nothing remote is

164consulted once that directory exists. The command the page offers therefore

165carries the build it belongs to (`fill.tgz?v=<commit>`), which makes every

166deployment a new spec and so a fresh install. The bare URL above is right the

167first time and stale ever after; `--help` says which build is running.

168

c2317d0 Fill the cache from the command line, without a browserJeremy Magland 8 days ago169The walk, the runs and the uploads are the page's own — the same modules under

170[`src/cache/`](src/cache/), driven by console output instead of a status bar

171(see [`src/cli/fill.ts`](src/cli/fill.ts)). What differs is the WebGPU: node

172has none, so the command line brings its own, the optional `webgpu` package of

173prebuilt [Google Dawn](https://dawn.googlesource.com/dawn) binaries, installed

174under the globals the transform code expects. Dawn reaches the GPU through

175Vulkan on Linux and Windows and Metal on macOS, so a machine wanting to

176contribute needs a GPU and its driver — on a machine without one, Dawn

177either finds no adapter at all or falls back to a software rasterizer, which

178is roughly a thousand times slower and worth nothing to anybody. The command

179names its adapter on startup, reports its rate in steps per second, and says

180so plainly when either looks wrong; it does not refuse to run, since the

181judgment is the operator's.

182

d71391e Fold the troubleshooting into the page, beside the commandJeremy Magland 8 days ago183A machine can also be too old for the command in a way that has nothing to do

184with its GPU. Dawn's prebuilt binary wants glibc 2.34, which a long-lived

185Linux workstation may well not have — Rocky and RHEL 8 are on 2.28 — and the

186obvious remedy of running the command in a container turns out not to work:

187inside one the NVIDIA driver declines to bring up its Vulkan driver

188(`vk_icdNegotiateLoaderICDInterfaceVersion` returns

189`VK_ERROR_INITIALIZATION_FAILED`), while the same call on the host succeeds.

190What does work is to borrow only the userland from a container image and run

191node through its loader, on the host, leaving the GPU, `/dev` and `/proc`

192exactly as they were; the host's own `/usr/lib64` stays last on the library

193path, since the NVIDIA libraries and the Vulkan loader have to match the

194running kernel module. The page carries that recipe, folded away beside the

195command it belongs to, along with what the other common failures mean —