BiCG iterations on one 12×12 system against the distance of the shadow vector from a breakdown
At its defaults it draws bicg iterations on one 12×12 system against the distance of the shadow vector from a breakdown. The matrix, the right-hand side and the answer are the same at every stop. The only thing that moves is r̃₀, the second starting vector, which the method requires and for which every account gives the same non-reason. At η = 0.01 from the surface where the second divisor vanishes, BiCG is the direct method it is advertised as and finishes in 12 steps on 12 unknowns. The steps then run 12, 12, 13, 17, 20, 24, 80, 80, 80, 80 as η falls, and at 10⁻¹¹ the method has not converged after 80. Wherever it does finish it finishes at the same accuracy — the cost is the guarantee, not the answer.
shadow-cost is one function in lib/figures/breakdown.js —
breakdown — the zero that is an answer, and the zero that is nothing. 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.
The matrix, the right-hand side and the answer are the same at every stop. The only thing that moves is r̃₀, the second starting vector, which the method requires and for which every account gives the same non-reason. At η = 0.01 from the surface where the second divisor vanishes, BiCG is the direct method it is advertised as and finishes in 12 steps on 12 unknowns. The steps then run 12, 12, 13, 17, 20, 24, 80, 80, 80, 80 as η falls, and at 10⁻¹¹ the method has not converged after 80. Wherever it does finish it finishes at the same accuracy — the cost is the guarantee, not the answer.
n: 12
The arguments are the ones The number that is re-derived passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
The matrix, the right-hand side and the answer are the same at every stop. The only thing that moves is r̃₀, the second starting vector, which the method requires and for which every account gives the same non-reason. At η = 0.01 from the surface where the second divisor vanishes, BiCG is the direct method it is advertised as and finishes in 12 steps on 12 unknowns. The steps then run 12, 12, 13, 17, 20, 24, 80, 80, 80, 80 as η falls, and at 10⁻¹¹ the method has not converged after 80. Wherever it does finish it finishes at the same accuracy — the cost is the guarantee, not the answer.
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.
6 distinct claims across 2 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 sign change in the second divisor along the shadow line
a size at which finite termination is visible inside the iteration budget
and close to it, it does not terminate at all
far from the surface the method terminates in about n steps
over at least seven decades
the divisor falls at every stop
Against the rule
It draws a decomposition and prints its residual. It calls
shadowSweep,
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 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.
The number that is re-derived
GMRES prints a residual it never computes from its answer either. On the matrix that sends a conjugate gradient recurrence 7.3·10¹⁰ wrong, and on two others chosen to be worse, its number is never more than a factor of 2.86 out — while the basis it is computed from has lost orthogonality entirely. The disease is not iterative methods, and it is not floating point.
Iterating, instead of factorisingThe same zero, and nothing was found
Change the recurrence by two lines and the divisor stops being a norm. It becomes an inner product of two vectors from two different sequences, and an inner product of two different vectors is zero on a whole hyperplane — with neither vector anywhere near zero, nothing invariant, and nothing converged. The arithmetic event is identical and the meaning is opposite.