probe-ceiling
At its defaults it draws how many eigenvalues a contour method can return: the probe block is a ceiling and does not say so. Beyn's method probes the contour with a random 4 × ℓ block V and reads the eigenvalues out of the rank of ∮T(z)⁻¹V dz. That rank is at most ℓ whatever is inside, so a probe block narrower than the number of eigenvalues present returns ℓ of them — with small residuals, and with nothing in the returned object to say that there were more. Measured with 4 eigenvalues inside |z| = 4: the rank is 1, 2, 3, 4, 4 at ℓ = 1, 2, 3, 4, 5, rising with the probe count and then stopping at 4. A caller who asked for two gets two. The counting integral is the check that says so, and it costs one more pass round the same contour.
probe-ceiling is one function in lib/figures/nlevp.js —
infinitely many eigenvalues — a contour that counts, and the probe block that is a ceiling. 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.
Beyn's method probes the contour with a random 4 × ℓ block V and reads the eigenvalues out of the rank of ∮T(z)⁻¹V dz. That rank is at most ℓ whatever is inside, so a probe block narrower than the number of eigenvalues present returns ℓ of them — with small residuals, and with nothing in the returned object to say that there were more. Measured with 4 eigenvalues inside |z| = 4: the rank is 1, 2, 3, 4, 4 at ℓ = 1, 2, 3, 4, 5, rising with the probe count and then stopping at 4. A caller who asked for two gets two. The counting integral is the check that says so, and it costs one more pass round the same contour.
radius: 4
The arguments are the ones A problem with infinitely many eigenvalues 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.
Beyn's method probes the contour with a random 4 × ℓ block V and reads the eigenvalues out of the rank of ∮T(z)⁻¹V dz. That rank is at most ℓ whatever is inside, so a probe block narrower than the number of eigenvalues present returns ℓ of them — with small residuals, and with nothing in the returned object to say that there were more. Measured with 4 eigenvalues inside |z| = 4: the rank is 1, 2, 3, 4, 4 at ℓ = 1, 2, 3, 4, 5, rising with the probe count and then stopping at 4. A caller who asked for two gets two. The counting integral is the check that says so, and it costs one more pass round the same contour.
radius: 2
The arguments are the ones A problem with infinitely many eigenvalues 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.
Beyn's method probes the contour with a random 4 × ℓ block V and reads the eigenvalues out of the rank of ∮T(z)⁻¹V dz. That rank is at most ℓ whatever is inside, so a probe block narrower than the number of eigenvalues present returns ℓ of them — with small residuals, and with nothing in the returned object to say that there were more. Measured with 2 eigenvalues inside |z| = 2: the rank is 1, 2, 2, 2, 2 at ℓ = 1, 2, 3, 4, 5, rising with the probe count and then stopping at 2. A caller who asked for two gets two. The counting integral is the check that says so, and it costs one more pass round the same contour.
radius: 5
The arguments are the ones A problem with infinitely many eigenvalues 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.
Beyn's method probes the contour with a random 4 × ℓ block V and reads the eigenvalues out of the rank of ∮T(z)⁻¹V dz. That rank is at most ℓ whatever is inside, so a probe block narrower than the number of eigenvalues present returns ℓ of them — with small residuals, and with nothing in the returned object to say that there were more. Measured with 12 eigenvalues inside |z| = 5: the rank is 1, 2, 3, 4, 4 at ℓ = 1, 2, 3, 4, 5, rising with the probe count and then stopping at 4, which is the SIZE of the problem rather than the number of eigenvalues — a second ceiling, because an 4 × ℓ block cannot have rank above 4 whatever is inside the contour. A caller who asked for two gets two. The counting integral is the check that says so, and it costs one more pass round the same contour.
radius: 3
The arguments are the ones A problem with infinitely many eigenvalues 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.
Beyn's method probes the contour with a random 4 × ℓ block V and reads the eigenvalues out of the rank of ∮T(z)⁻¹V dz. That rank is at most ℓ whatever is inside, so a probe block narrower than the number of eigenvalues present returns ℓ of them — with small residuals, and with nothing in the returned object to say that there were more. Measured with 3 eigenvalues inside |z| = 3: the rank is 1, 2, 3, 3, 3 at ℓ = 1, 2, 3, 4, 5, rising with the probe count and then stopping at 3. A caller who asked for two gets two. The counting integral is the check that says so, and it costs one more pass round the same contour.
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.
5 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 contour with something inside it
a size the contour integrals can afford
a size the probes can be run at
LU is for square matrices
the rank is the smallest of the probe count, the count inside and the size
Against the rule
It draws a decomposition and prints its residual. It calls
beynRank, countInside,
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 173
of 325 generators —
158 print a residual and
15 are exempt with a published reason;
152 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 problem with infinitely many eigenvalues
Let the matrix depend on λ through something that is not a polynomial and three things stop being true at once. There is no linearisation, there is no characteristic polynomial, and "compute the spectrum" is not a request that can be granted — the only finite question is how many eigenvalues are inside this circle.
Randomised, and the guarantee that changes kindCounting what is inside a circle
A trace of a matrix nobody wants to form, integrated around a contour, gives an integer — how many eigenvalues are inside. It converges exponentially, it is estimated with random probes, and the probe block is a ceiling that the answer does not mention.
Where the flop count stopped predicting the timeThe last digit is the cheapest
Every cost curve on this site has the same shape: the first digits are cheap and the last ones are not. One method inverts it. Doubling the work buys twice as many digits as the previous doubling did, so the price of a digit halves every time it is paid.