Relative error of scaling and squaring against the number of squarings, μ = 4
At its defaults it draws relative error of scaling and squaring against the number of squarings, μ = 4. Each point computes e^(A/2ˢ) by a Padé approximant and squares it s times, against a closed-form exponential. At s = 0 the approximant is being used far outside its range and the error is 6·10⁻¹²; the best is 6.88·10⁻¹⁶ at s = 2; at s = 15 it has risen again to 3.16·10⁻¹². The right-hand rise is the squaring phase amplifying its own rounding, which is why a library chooses s from ‖A‖ rather than taking as many as it can afford.
squaring-cost is one function in lib/figures/funm.js —
matrix functions — the definition that is not a method, and the vector that was wanted. 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 point computes e^(A/2ˢ) by a Padé approximant and squares it s times, against a closed-form exponential. At s = 0 the approximant is being used far outside its range and the error is 6·10⁻¹²; the best is 6.88·10⁻¹⁶ at s = 2; at s = 15 it has risen again to 3.16·10⁻¹². The right-hand rise is the squaring phase amplifying its own rounding, which is why a library chooses s from ‖A‖ rather than taking as many as it can afford.
mu: 4
The arguments are the ones A coin flip that fixes the average passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
Each point computes e^(A/2ˢ) by a Padé approximant and squares it s times, against a closed-form exponential. At s = 0 the approximant is being used far outside its range and the error is 6·10⁻¹²; the best is 6.88·10⁻¹⁶ at s = 2; at s = 15 it has risen again to 3.16·10⁻¹². The right-hand rise is the squaring phase amplifying its own rounding, which is why a library chooses s from ‖A‖ rather than taking as many as it can afford.
mu: 1
The arguments are the ones The error the method already knows passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
Each point computes e^(A/2ˢ) by a Padé approximant and squares it s times, against a closed-form exponential. At s = 0 the approximant is being used far outside its range and the error is 4.01·10⁻¹⁵; the best is 2.12·10⁻¹⁶ at s = 1; at s = 15 it has risen again to 3.16·10⁻¹². The right-hand rise is the squaring phase amplifying its own rounding, which is why a library chooses s from ‖A‖ rather than taking as many as it can afford.
mu: 12
The arguments are the ones The error the method already knows passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
Each point computes e^(A/2ˢ) by a Padé approximant and squares it s times, against a closed-form exponential. At s = 0 the approximant is being used far outside its range and the error is 5.55·10⁻¹¹; the best is 9.08·10⁻¹⁶ at s = 2; at s = 15 it has risen again to 3.16·10⁻¹². The right-hand rise is the squaring phase amplifying its own rounding, which is why a library chooses s from ‖A‖ rather than taking as many as it can afford.
What it checked while drawing
Every figure above checked its own claims on the way to being drawn, and a claim that failed
would have stopped the picture rather than shipped a wrong one. Those checks 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.
7 distinct claims across 4 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 size the sweep of exponentials can afford
a superdiagonal the closed form stays representable at
and too many costs as well
LU is for square matrices
matmul shapes agree
the best number of squarings is inside the sweep
too few squarings costs
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 217
of 397 generators —
199 print a residual and
18 are exempt with a published reason;
180 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 coin flip that fixes the average
Add 0.1 to 256 a thousand times at eight significand bits and the answer is 256. Not approximately — the total never moves, not once, and no error bound says so. Round up one time in twenty instead of never, and it arrives at 348 against a true 356.
Eigenvalues, singular values, rankThe error the method already knows
Summing the exponential's Taylor series throws away a known number of digits, and the number is on the machine while the sum is being formed. The largest term divided by the answer, times the unit roundoff, tracks the relative error that comes out — to within a factor of nine, across fourteen orders of magnitude of it — and nothing reports it.