Overview: the cymbal tier is now cymbal2
1 changed file+11−13
README.mdmodified+11−13View file
@@ -8,7 +8,7 @@ The results are published as static sites, one per tier:
88 | --- | --- | --- |
99 | 0, string | [challenges/string](https://vault1.magland.org/challenges/string) | [results](https://vault1.magland.org/challenges/string/site/) |
1010 | 1, plate | [challenges/plate](https://vault1.magland.org/challenges/plate) | [results](https://vault1.magland.org/challenges/plate/site/) |
11-| 2, cymbal | [challenges/cymbal](https://vault1.magland.org/challenges/cymbal) | [results](https://vault1.magland.org/challenges/cymbal/site/) |
11+| 2, cymbal | [challenges/cymbal2](https://vault1.magland.org/challenges/cymbal2) | [results](https://vault1.magland.org/challenges/cymbal2/site/) |
1212
1313 ## Background
1414
@@ -22,8 +22,8 @@ There is no externally supplied ground truth. The reference for each challenge i
2222
2323 Each tier is a pair of repositories, plus shared tooling.
2424
25-- **A challenge repository** (`challenges/string`, `challenges/plate`, `challenges/cymbal`) holds the specifications: one directory per challenge with a `README.md`, which is the authoritative definition, and a `challenge.json`, which repeats the parameters, output format, error measures, and the grid of the optional field export in machine-readable form. It also holds a registry of solution repositories and the workflow that builds the comparison site.
26-- **Solution repositories** (`challenges/string-solutions`, `challenges/plate-solutions`, `challenges/cymbal-solutions`, and any others that are registered) hold submissions: a JSON file per submission with metadata and one or more solutions, the output wav files, optional field exports for visualization, and whatever else the authors want, such as solver code or their own visualization site. A solution repository runs only the validator; it makes no comparisons of its own.
25+- **A challenge repository** (`challenges/string`, `challenges/plate`, `challenges/cymbal2`) holds the specifications: one directory per challenge with a `README.md`, which is the authoritative definition (the cymbal tier defines its model once, in a `MODEL.md` that every challenge refers to), and a `challenge.json`, which repeats the parameters, output format, error measures, and the grid of the optional field export in machine-readable form. It also holds a registry of solution repositories and the workflow that builds the comparison site.
26+- **Solution repositories** (`challenges/string-solutions`, `challenges/plate-solutions`, `challenges/cymbal2-solutions`, and any others that are registered) hold submissions: a JSON file per submission with metadata and one or more solutions, the output wav files, optional field exports for visualization, and whatever else the authors want, such as solver code or their own visualization site. A solution repository runs only the validator; it makes no comparisons of its own.
2727 - **The tools** (`challenges/challenge-tools`) are a small Python package with the submission schema, the validator, the error measures, the reference-selection rule, and the generator of the comparison site. Every challenge repository installs it in its workflow.
2828
2929 The comparison workflow of a challenge repository clones every registered solution repository, reads the committed output files, computes every pairwise error, chooses the reference, and deploys the site. It runs on every push to the challenge repository or when dispatched by hand. Nothing in the vault triggers across repositories, so a push to a solution repository is picked up at the next run of the challenge repository's workflow. All solvers run on the submitters' own machines; the workflow runner only scores committed files.
@@ -51,17 +51,14 @@ The rule is only as good as the assertions. A sequence that is not in fact monot
5151 | [string-pluck-v1](https://vault1.magland.org/challenges/string/blob/main/challenges/string-pluck-v1/README.md) | Damped string with fixed ends, released from its static equilibrium under a finger load | 2 s of pickup velocity |
5252 | [plate-strike-v1](https://vault1.magland.org/challenges/plate/blob/main/challenges/plate-strike-v1/README.md) | Free 12 in aluminum plate, linear 3D elastodynamics with Kelvin-Voigt damping, struck by a short force pulse | 3 s of radiated pressure by the Rayleigh integral |
5353 | [plate-strike-nl-v1](https://vault1.magland.org/challenges/plate/blob/main/challenges/plate-strike-nl-v1/README.md) | The same plate as a Saint Venant-Kirchhoff solid (geometrically nonlinear), struck by a soft mallet | 3 s of radiated pressure |
54-| [cymbal-flat-disk-v1](https://vault1.magland.org/challenges/cymbal/blob/main/challenges/cymbal-flat-disk-v1/README.md) | Flat, free 16 in bronze disk of uniform thickness, Saint Venant-Kirchhoff, struck near the rim by a stick-like pulse | 6 s of radiated pressure |
55-| [cymbal-bow-v1](https://vault1.magland.org/challenges/cymbal/blob/main/challenges/cymbal-bow-v1/README.md) | The same disk bowed into a shallow paraboloid (25 mm rise): the effect of curvature alone | 6 s of radiated pressure |
56-| [cymbal-bell-v1](https://vault1.magland.org/challenges/cymbal/blob/main/challenges/cymbal-bell-v1/README.md) | The bowed disk with a cosine-dome bell and a mounting hole: the effect of the bell alone | 6 s of radiated pressure |
57-| [cymbal-hammered-v1](https://vault1.magland.org/challenges/cymbal/blob/main/challenges/cymbal-hammered-v1/README.md) | The belled disk with 150 hammer dents at fixed positions: the effect of breaking the symmetry | 6 s of radiated pressure |
58-| [cymbal-tapered-v1](https://vault1.magland.org/challenges/cymbal/blob/main/challenges/cymbal-tapered-v1/README.md) | The hammered cymbal lathed to a taper (1.2 to 0.7 mm): the effect of the thickness profile | 6 s of radiated pressure |
54+| [cymbal2-flat-v1](https://vault1.magland.org/challenges/cymbal2/blob/main/challenges/cymbal2-flat-v1/README.md) | Flat 16 in bronze annulus of uniform thickness, geometrically nonlinear thin shell with its rigid motions held, struck three times by a drum stick (Hertz contact) near the center, at mid-radius and near the rim | 7 s of radiated pressure by the Rayleigh integral |
55+| [cymbal2-crash-v1](https://vault1.magland.org/challenges/cymbal2/blob/main/challenges/cymbal2-crash-v1/README.md) | The crash cymbal: paraboloidal bow, cosine-dome bell around the mounting hole, thickness tapering from 1.2 to 0.7 mm, the same three strikes | 7 s of radiated pressure |
5956
60-The string challenge is a hello world: its modal series solution is essentially exact, so it exercises the submission and scoring pipeline and gives a check on the reference rule. The plate challenges define three-dimensional models, so the thin-plate solutions submitted so far (Kirchhoff-Love finite elements for the linear plate, a modal von Kármán method for the nonlinear one) are approximations whose error relative to a future converged three-dimensional solution includes the modeling error of plate theory. Until such a solution arrives, the reference is the best thin-plate solution and the errors measure only differences within plate theory; the results pages say so. The cymbal tier starts from a flat disk and will add the features of a real cymbal one at a time (bell, bow, hammering, varying thickness), each as a new challenge, so that the effect of each on the sound and on the cost of computing it can be seen in isolation; its first solutions are von Kármán modal solutions on Cartesian grids that approximate the disk by a staircase.
57+The string challenge is a hello world: its modal series solution is essentially exact, so it exercises the submission and scoring pipeline and gives a check on the reference rule. The plate challenges define three-dimensional models, so the thin-plate solutions submitted so far (Kirchhoff-Love finite elements for the linear plate, a modal von Kármán method for the nonlinear one) are approximations whose error relative to a future converged three-dimensional solution includes the modeling error of plate theory. Until such a solution arrives, the reference is the best thin-plate solution and the errors measure only differences within plate theory; the results pages say so. The cymbal tier defines one geometrically nonlinear thin-shell model (Marguerre shallow shell with in-plane inertia, Kelvin-Voigt and mass-proportional damping) and two geometries, a flat annulus and a bowed, belled, tapered crash cymbal, each struck three times by a stick modeled as a point mass with a Hertz contact, so that the contact time and the energy of each hit follow from the local stiffness and the difference between a hit near the stiff center and a crash near the rim comes out of the same equations within one recording. An earlier version of this tier ([challenges/cymbal](https://vault1.magland.org/challenges/cymbal)), which added the features of a cymbal one at a time under a prescribed force pulse, is kept for reference; it showed that a prescribed pulse deposits the same energy wherever it lands on a uniform plate, which is why the stick model replaced it.
6158
6259 ## Conventions
6360
64-- **Free bodies.** The plates and disks are free, and the strikes impart momentum and angular momentum. The outputs are defined with the rigid motion linearized: the acceleration relative to the best-fit rigid frame plus that frame's translational and angular acceleration, which keeps the kick of the strike in the sound and leaves out the slow turning of the body that only an exact three-dimensional solution would show. For modal thin-plate solvers this is what they compute with their rigid modes included.
61+- **Rigid motion.** The plates of tier 1 are free, and their outputs are defined with the rigid motion linearized: the acceleration relative to the best-fit rigid frame plus that frame's translational and angular acceleration. The cymbal tier instead holds the six rigid motions of the shell (an ideal support that fixes position and orientation and constrains no deformation), because the shallow-shell strains are not invariant under finite rotations and a free, tilting shell would behave as a curved one.
6562 - A challenge is never changed once solutions from others exist for it. A corrected or modified model gets a new identifier, for example a `-v2` suffix.
6663 - Identifiers (challenges, submissions, solutions) are lowercase letters, digits, and hyphens.
6764 - Field exports for visualization are HDF5 files on a grid recommended by the challenge; they are not scored. Files of a few megabytes live in plain git, larger ones in git LFS or at an external URL.
@@ -75,7 +72,7 @@ The string challenge is a hello world: its modal series solution is essentially
7572
7673 ## Roadmap
7774
78-The tiers sketched in the research plan, for a cymbal as the running example, are: a flat plate struck at a point (tier 1, done in linear and nonlinear form); a curved, cymbal-shaped shell (tier 2, begun with the flat disk); large-amplitude strikes with geometric nonlinearity on that shell (tier 3); and sound radiated into the surrounding air by a coupled structure and acoustic simulation (tier 4), replacing the Rayleigh integral used so far. Alongside the tiers we intend to pursue simulations of complete instruments, starting with a cymbal on a stand, which are harder to benchmark but show which effects matter most for the sound and so guide which challenges to add. Open questions include which errors are audible, since a cheaper model can have a large waveform error yet sound identical, and the collection is a natural place to host listening tests once there are enough solutions to compare.
75+The tiers sketched in the research plan, for a cymbal as the running example, are: a flat plate struck at a point (tier 1, done in linear and nonlinear form); a curved, cymbal-shaped shell with large-amplitude strikes and geometric nonlinearity (tiers 2 and 3, combined in the cymbal tier); and sound radiated into the surrounding air by a coupled structure and acoustic simulation (tier 4), replacing the Rayleigh integral used so far. Alongside the tiers we intend to pursue simulations of complete instruments, starting with a cymbal on a stand, which are harder to benchmark but show which effects matter most for the sound and so guide which challenges to add. Open questions include which errors are audible, since a cheaper model can have a large waveform error yet sound identical, and the collection is a natural place to host listening tests once there are enough solutions to compare.
7976
8077 ## Repositories in this collection
8178
@@ -87,5 +84,6 @@ The tiers sketched in the research plan, for a cymbal as the running example, ar
8784 | [string-solutions](https://vault1.magland.org/challenges/string-solutions) | solutions to the string challenges, with a 2D field viewer |
8885 | [plate](https://vault1.magland.org/challenges/plate) | tier 1 specifications, registry, comparison site |
8986 | [plate-solutions](https://vault1.magland.org/challenges/plate-solutions) | solutions to the plate challenges, with a 3D field viewer |
90-| [cymbal](https://vault1.magland.org/challenges/cymbal) | tier 2 specifications, registry, comparison site |
91-| [cymbal-solutions](https://vault1.magland.org/challenges/cymbal-solutions) | solutions to the cymbal challenges, with a 3D field viewer |
87+| [cymbal2](https://vault1.magland.org/challenges/cymbal2) | tier 2 specifications (model document, two challenges), registry, comparison site with interactive 3D models of the geometries |
88+| [cymbal2-solutions](https://vault1.magland.org/challenges/cymbal2-solutions) | solutions to the cymbal challenges (finite element and modal solvers on the same mesh), with a 3D field viewer |
89+| [cymbal](https://vault1.magland.org/challenges/cymbal), [cymbal-solutions](https://vault1.magland.org/challenges/cymbal-solutions) | the earlier version of the cymbal tier, superseded by cymbal2 and kept for reference |