irka-shifts
At its defaults it draws irka's interpolation points walking to the condition that defines them. Each curve is one of 4 interpolation points across 13 iterations of σ ← −λ(Aᵣ). They start logarithmically spread over the frequency range, which is a guess, and settle at 9.861, 40.15, 102.1, 302.8. What is checked at the end is not that they stopped moving but that where they stopped is the first-order condition: the mirrored poles of the model they produced agree with them to 2.81·10⁻¹². A fixed-point iteration that stops moving without satisfying its own condition has converged to nothing, and this one has no convergence proof to lean on — so the condition is checked rather than the movement.
irka-shifts is one function in lib/figures/ratkrylov.js —
matching the function where you choose — interpolation points, the basis they need, and the fixed point. Everything below came out of it during this build, at
arguments taken from the essays rather than invented for this page. A figure here is the
figure a reader meets in an essay, and if the generator changes, this page changes with it.
At its defaults
Drawn even though every essay passes arguments — which on this site is every essay, at 100% of placements since the standard pass. A default nothing exercises is a trap for the next essay to call this with none, and this is the page where a default that has drifted from the figures around it becomes visible.
Each curve is one of 4 interpolation points across 13 iterations of σ ← −λ(Aᵣ). They start logarithmically spread over the frequency range, which is a guess, and settle at 9.861, 40.15, 102.1, 302.8. What is checked at the end is not that they stopped moving but that where they stopped is the first-order condition: the mirrored poles of the model they produced agree with them to 2.81·10⁻¹². A fixed-point iteration that stops moving without satisfying its own condition has converged to nothing, and this one has no convergence proof to lean on — so the condition is checked rather than the movement.
r: 4
The arguments are the ones A basis that is the same subspace and not the same thing passes. A value drawn at the generator's defaults instead would be a picture no essay asked for and no assertion has been run against.
Each curve is one of 4 interpolation points across 13 iterations of σ ← −λ(Aᵣ). They start logarithmically spread over the frequency range, which is a guess, and settle at 9.861, 40.15, 102.1, 302.8. What is checked at the end is not that they stopped moving but that where they stopped is the first-order condition: the mirrored poles of the model they produced agree with them to 2.81·10⁻¹². A fixed-point iteration that stops moving without satisfying its own condition has converged to nothing, and this one has no convergence proof to lean on — so the condition is checked rather than the movement.
r: 2
The arguments are the ones Interpolating at the model’s own poles passes. A value drawn at the generator's defaults instead would be a picture no essay asked for and no assertion has been run against.
Each curve is one of 2 interpolation points across 14 iterations of σ ← −λ(Aᵣ). They start logarithmically spread over the frequency range, which is a guess, and settle at 10.31, 67.52. What is checked at the end is not that they stopped moving but that where they stopped is the first-order condition: the mirrored poles of the model they produced agree with them to 1.44·10⁻¹¹. A fixed-point iteration that stops moving without satisfying its own condition has converged to nothing, and this one has no convergence proof to lean on — so the condition is checked rather than the movement.
r: 3
The arguments are the ones Interpolating at the model’s own poles passes. A value drawn at the generator's defaults instead would be a picture no essay asked for and no assertion has been run against.
Each curve is one of 3 interpolation points across 15 iterations of σ ← −λ(Aᵣ). They start logarithmically spread over the frequency range, which is a guess, and settle at 9.91, 45.25, 156. What is checked at the end is not that they stopped moving but that where they stopped is the first-order condition: the mirrored poles of the model they produced agree with them to 4.06·10⁻¹². A fixed-point iteration that stops moving without satisfying its own condition has converged to nothing, and this one has no convergence proof to lean on — so the condition is checked rather than the movement.
r: 5
The arguments are the ones Interpolating at the model’s own poles passes. A value drawn at the generator's defaults instead would be a picture no essay asked for and no assertion has been run against.
Each curve is one of 5 interpolation points across 11 iterations of σ ← −λ(Aᵣ). They start logarithmically spread over the frequency range, which is a guess, and settle at 9.857, 39.35, 90.51, 193.8, 432.9. What is checked at the end is not that they stopped moving but that where they stopped is the first-order condition: the mirrored poles of the model they produced agree with them to 7.14·10⁻¹². A fixed-point iteration that stops moving without satisfying its own condition has converged to nothing, and this one has no convergence proof to lean on — so the condition is checked rather than the movement.
r: 6
The arguments are the ones Interpolating at the model’s own poles passes. A value drawn at the generator's defaults instead would be a picture no essay asked for and no assertion has been run against.
Each curve is one of 6 interpolation points across 10 iterations of σ ← −λ(Aᵣ). They start logarithmically spread over the frequency range, which is a guess, and settle at 9.857, 39.27, 88.05, 162.2, 297, 524.7. What is checked at the end is not that they stopped moving but that where they stopped is the first-order condition: the mirrored poles of the model they produced agree with them to 1.95·10⁻¹³. A fixed-point iteration that stops moving without satisfying its own condition has converged to nothing, and this one has no convergence proof to lean on — so the condition is checked rather than the movement.
What it checked while drawing
Every figure above asserted its own claims on the way to being drawn, and a claim that failed
would have failed the build rather than drawn a wrong picture. Those assertions used to leave
no trace at all: a passing one returned true and the only evidence the figure had
checked anything was that nothing crashed. The list below is what they actually said, collected
by running this generator with an observer installed — not a description of
what it is believed to check.
12 distinct claims across 6 sets of arguments, grouped below by shape — because most of them are one sentence with a different number in it, and how many separate times that sentence was put to the test is the informative part.
a degree the state dimension can carry
a grid fine enough to have modes and coarse enough to draw
a Lyapunov equation with a solution
a projection that exists
an actuator and a sensor on the grid
an interpolation point that adds a direction
an order the iteration can carry
and the shifts are its own mirrored poles there
LU is for square matrices
matmul shapes agree
the iteration reached a fixed point
the projection is biorthogonal as normalised
Against the rule
It draws a decomposition and prints its residual. It calls
irka, poles, h2Error,
and every figure above carries the badge — which residualcheck verifies by looking
for it in the emitted SVG rather than by finding the call that builds one. A badge that is
constructed and then left out of the body is the failure that check exists for.
Across the library: the rule bites on 192
of 346 generators —
174 print a residual and
18 are exempt with a published reason;
154 factorise nothing.
Read from lib/residual-rule.js, which is the same body the gate enforces from,
and the gate's last check fails the build if this page and it disagree about any generator.
Where it is called
Changing this generator changes every figure on this list. That is what makes the list worth publishing rather than keeping in a check script.
A basis that is the same subspace and not the same thing
The interpolation conditions are conditions on a subspace, so any basis of it will do. The one a derivation writes down reaches a condition number of 7.7·10⁹ by its eighth vector, and the rate at which it gets there is set by a number the user chose with no information.
Reduction, and what a model is forExact at the points that were named
Balanced truncation asks for nothing and bounds everything, at a cost no large model can pay. The other kind of reduction asks for r numbers, costs r solves, is exact at every one of them — and bounds nothing anywhere else. That trade is the whole of large-scale model reduction.
Reduction, and what a model is forInterpolating at the model’s own poles
One choice of interpolation points is not arbitrary — the mirrored poles of the model about to be built. It is a fixed point rather than a guess, and when it is reached it beats a method costing O(n³) — by 0.4 per cent, which is the honest size of the whole contest.