Generator

window-drift

One function in the seqstab library, called 11 times across 4 essays. Below: what it draws at its defaults, what it draws at every value an essay asks for, the 9 claims it put to the test while drawing them, and where it stands against the rule this site is named for.

At its defaults it draws how far a carried triangular factor drifts from the data, over 2976 steps of a sliding window. A window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 3.87·10⁻¹⁴ from the matrix it is supposed to factor — a fitted slope of 0.554 in the step count, against a bound whose slope is 1.

window-drift is one function in lib/figures/seqstab.js — accumulation — what a carried factor collects, and why it is a walk rather than a sum. 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.

How far a carried triangular factor drifts from the data, over 2976 steps of a sliding windowA window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 3.87·10⁻¹⁴ from the matrix it is supposed to factor — a fitted slope of 0.554 in the step count, against a bound whose slope is 1.10²10³10⁴10⁻¹⁷10⁻¹⁶10⁻¹⁵10⁻¹⁴10⁻¹³10⁻¹²steps taken‖RᵀR − AᵀA‖ ⁄ ‖AᵀA‖the bound, linear in the steps√k · uevery step safe, the chain notdrift after the run3.9·10⁻¹⁴the bound there3.3·10⁻¹³√k · u there6.1·10⁻¹⁵worst single amplification2.7worst leverage met0.69refactorisations1backward stable onceand three thousand times is a different claim

A window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 3.87·10⁻¹⁴ from the matrix it is supposed to factor — a fitted slope of 0.554 in the step count, against a bound whose slope is 1.

refresh: 0

The arguments are the ones Stable once, and three thousand times 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.

How far a carried triangular factor drifts from the data, over 2976 steps of a sliding windowA window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 3.87·10⁻¹⁴ from the matrix it is supposed to factor — a fitted slope of 0.554 in the step count, against a bound whose slope is 1.10²10³10⁴10⁻¹⁷10⁻¹⁶10⁻¹⁵10⁻¹⁴10⁻¹³10⁻¹²steps taken‖RᵀR − AᵀA‖ ⁄ ‖AᵀA‖the bound, linear in the steps√k · uevery step safe, the chain notdrift after the run3.9·10⁻¹⁴the bound there3.3·10⁻¹³√k · u there6.1·10⁻¹⁵worst single amplification2.7worst leverage met0.69refactorisations1backward stable onceand three thousand times is a different claim

A window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 3.87·10⁻¹⁴ from the matrix it is supposed to factor — a fitted slope of 0.554 in the step count, against a bound whose slope is 1.

refresh: 500

The arguments are the ones Stable once, and three thousand times 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.

How far a carried triangular factor drifts from the data, over 2976 steps of a sliding windowA window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows except every 500 steps. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 1.27·10⁻¹⁴ from the matrix it is supposed to factor, against 3.87·10⁻¹⁴ with no refresh at all.10²10³10⁴10⁻¹⁹10⁻¹⁸10⁻¹⁷10⁻¹⁶10⁻¹⁵10⁻¹⁴10⁻¹³10⁻¹²steps taken‖RᵀR − AᵀA‖ ⁄ ‖AᵀA‖the bound, linear in the steps√k · uevery step safe, the chain notdrift after the run1.3·10⁻¹⁴the bound there3.3·10⁻¹³√k · u there6.1·10⁻¹⁵worst single amplification2.7worst leverage met0.69refactorisations6backward stable onceand three thousand times is a different claim

A window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows except every 500 steps. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 1.27·10⁻¹⁴ from the matrix it is supposed to factor, against 3.87·10⁻¹⁴ with no refresh at all.

refresh: 100

The arguments are the ones Stable once, and three thousand times 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.

How far a carried triangular factor drifts from the data, over 2976 steps of a sliding windowA window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows except every 100 steps. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 2.48·10⁻¹⁵ from the matrix it is supposed to factor, against 3.87·10⁻¹⁴ with no refresh at all.10²10³10⁴10⁻¹⁹10⁻¹⁸10⁻¹⁷10⁻¹⁶10⁻¹⁵10⁻¹⁴10⁻¹³10⁻¹²steps taken‖RᵀR − AᵀA‖ ⁄ ‖AᵀA‖the bound, linear in the steps√k · uevery step safe, the chain notdrift after the run2.5·10⁻¹⁵the bound there3.3·10⁻¹³√k · u there6.1·10⁻¹⁵worst single amplification2.7worst leverage met0.69refactorisations30backward stable onceand three thousand times is a different claim

A window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows except every 100 steps. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 2.48·10⁻¹⁵ from the matrix it is supposed to factor, against 3.87·10⁻¹⁴ with no refresh at all.

refresh: 25

The arguments are the ones Stable once, and three thousand times 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.

How far a carried triangular factor drifts from the data, over 2976 steps of a sliding windowA window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows except every 25 steps. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 8.72·10⁻¹⁹ from the matrix it is supposed to factor, against 3.87·10⁻¹⁴ with no refresh at all.10²10³10⁴10⁻²²10⁻²⁰10⁻¹⁸10⁻¹⁶10⁻¹⁴10⁻¹²steps taken‖RᵀR − AᵀA‖ ⁄ ‖AᵀA‖the bound, linear in the steps√k · uevery step safe, the chain notdrift after the run8.7·10⁻¹⁹the bound there3.3·10⁻¹³√k · u there6.1·10⁻¹⁵worst single amplification2.7worst leverage met0.69refactorisations120backward stable onceand three thousand times is a different claim

A window of 24 rows on 6 columns, moved one row at a time: each step folds a row in with Givens rotations and removes one with hyperbolic rotations, and the factor is never rebuilt from the rows except every 25 steps. The rows are integers times powers of two, so AᵀA is exact in a double and the vertical axis is a distance from the answer. No single step amplifies by more than 2.72, no downdate fails, and after 2976 steps the factor is 8.72·10⁻¹⁹ from the matrix it is supposed to factor, against 3.87·10⁻¹⁴ with no refresh at all.

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.

9 distinct claims across 5 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 column count the exact Gram matrix stays inside a double for

a refresh period inside the range the run is drawn over

a run long enough to fit a slope

a spread of scales the integers survive

a window wider than the number of columns, or the factor is singular

and grows as the square root of the number of steps rather than in proportion to it

and the drift stays inside the bound that is linear in the steps

matmul shapes agree

no downdate in the run fails

Against the rule

The rule does not apply to it. It factorises nothing, so there is no residual it could be withholding. That is worth stating rather than leaving blank: a site that reported the rule as satisfied by every generator would be counting mostly generators the rule never reached.

Across the library: the rule bites on 113 of 238 generators — 98 print a residual and 15 are exempt with a published reason; 125 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.

When the problem arrives again

Stable once, and three thousand times

A sliding window adds a row and removes one at every step and never looks at the data again. No single step of it amplifies by more than 2.72, no downdate fails, and after three thousand steps the triangular factor in memory is 3.9·10⁻¹⁴ from the matrix it is supposed to be a factor of — six hundred times growth from a per-step bound that says nothing about chains.

When the problem arrives again

The problem that arrives again

A hundred and thirty essays have solved a system once and measured how wrong the answer was. Almost no computation is shaped like that. A solve is one step of an outer loop, its answer is an input rather than a deliverable, and four quantities this collection has treated as accuracy requirements turn out to be assets with a shelf life.

Iterating, instead of factorising

The residual the method reports

Conjugate gradients prints a relative residual of 6.9·10⁻²¹. The unit roundoff is 1.1·10⁻¹⁶, so that is not a small residual and not a large one — it is not a residual. The vector the method is holding at that step has ‖b − Ax‖/‖b‖ = 5.1·10⁻¹⁰, and nothing in the run says so.

The arithmetic underneath

Three walks and one bound

A left-to-right sum, a chain of three thousand rotations and a conjugate gradient residual recurrence share no arithmetic and no vocabulary. Each has a standard bound that is linear in whatever it accumulates against. All three come out at a half — 0.486, 0.554 and 0.507 — and nothing is rescaled.

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