Conjugate gradients on the three-dimensional model problem with every iterate cut to rank 3
At its defaults it draws conjugate gradients on the three-dimensional model problem with every iterate cut to rank 3. The falling curves are relative residuals: the lower one is the same method with no budget, which reaches 1.61·10⁻¹⁴ in 40 steps, and the upper one is the budgeted run, which stops at 3.85·10⁻⁴. The two step curves near the top are ranks, on their own scale: the un-truncated step asks for 5 at every step from the third onwards and the budget allows 3. The truncation is therefore not an occasional tidy-up — it is happening at every step, and the distance between the two residual curves is what it costs. The solution of this problem is itself a train of rank five, so a budget of five or more removes nothing and the two curves coincide.
truncated-cg is one function in lib/figures/ttrain.js —
the train — one rank per cut of the index list, and the iterate that must be cut back. 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 falling curves are relative residuals: the lower one is the same method with no budget, which reaches 1.61·10⁻¹⁴ in 40 steps, and the upper one is the budgeted run, which stops at 3.85·10⁻⁴. The two step curves near the top are ranks, on their own scale: the un-truncated step asks for 5 at every step from the third onwards and the budget allows 3. The truncation is therefore not an occasional tidy-up — it is happening at every step, and the distance between the two residual curves is what it costs. The solution of this problem is itself a train of rank five, so a budget of five or more removes nothing and the two curves coincide.
maxRank: 7
The arguments are the ones A run that is over at step five passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
The falling curves are relative residuals: the lower one is the same method with no budget, which reaches 1.61·10⁻¹⁴ in 40 steps, and the upper one is the budgeted run, which stops at 1.61·10⁻¹⁴. The two step curves near the top are ranks, on their own scale: the un-truncated step asks for 5 at every step from the third onwards and the budget allows 7. The truncation is therefore not an occasional tidy-up — it is happening at every step, and the distance between the two residual curves is what it costs. The solution of this problem is itself a train of rank five, so a budget of five or more removes nothing and the two curves coincide.
maxRank: 3
The arguments are the ones An iterate that must be made smaller passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
The falling curves are relative residuals: the lower one is the same method with no budget, which reaches 1.61·10⁻¹⁴ in 40 steps, and the upper one is the budgeted run, which stops at 3.85·10⁻⁴. The two step curves near the top are ranks, on their own scale: the un-truncated step asks for 5 at every step from the third onwards and the budget allows 3. The truncation is therefore not an occasional tidy-up — it is happening at every step, and the distance between the two residual curves is what it costs. The solution of this problem is itself a train of rank five, so a budget of five or more removes nothing and the two curves coincide.
maxRank: 1
The arguments are the ones An iterate that must be made smaller passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
The falling curves are relative residuals: the lower one is the same method with no budget, which reaches 1.61·10⁻¹⁴ in 40 steps, and the upper one is the budgeted run, which stops at 0.119. The two step curves near the top are ranks, on their own scale: the un-truncated step asks for 5 at every step from the third onwards and the budget allows 1. The truncation is therefore not an occasional tidy-up — it is happening at every step, and the distance between the two residual curves is what it costs. The solution of this problem is itself a train of rank five, so a budget of five or more removes nothing and the two curves coincide.
maxRank: 2
The arguments are the ones An iterate that must be made smaller passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
The falling curves are relative residuals: the lower one is the same method with no budget, which reaches 1.61·10⁻¹⁴ in 40 steps, and the upper one is the budgeted run, which stops at 0.0112. The two step curves near the top are ranks, on their own scale: the un-truncated step asks for 5 at every step from the third onwards and the budget allows 2. The truncation is therefore not an occasional tidy-up — it is happening at every step, and the distance between the two residual curves is what it costs. The solution of this problem is itself a train of rank five, so a budget of five or more removes nothing and the two curves coincide.
maxRank: 4
The arguments are the ones An iterate that must be made smaller passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
The falling curves are relative residuals: the lower one is the same method with no budget, which reaches 1.61·10⁻¹⁴ in 40 steps, and the upper one is the budgeted run, which stops at 6.32·10⁻⁶. The two step curves near the top are ranks, on their own scale: the un-truncated step asks for 5 at every step from the third onwards and the budget allows 4. The truncation is therefore not an occasional tidy-up — it is happening at every step, and the distance between the two residual curves is what it costs. The solution of this problem is itself a train of rank five, so a budget of five or more removes nothing and the two curves coincide.
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.
4 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 rank budget the solver is given
and the unbudgeted run goes at least as far
matmul shapes agree
the budget is what is kept
Against the rule
It draws a decomposition and prints its residual. It calls
truncatedCg,
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.
A run that is over at step five
A conjugate gradient whose every iterate is cut to a rank budget reaches the floor that budget allows at step 5, 36, 42 or 59, and then does nothing for the rest of the run. Four times the iterations move the floor by a factor of 1.8, and past the answer's own rank they move it the wrong way.
Iterating, instead of factorisingAn iterate that must be made smaller
Applying a Kronecker-sum operator to a low-rank iterate multiplies its ranks by d and adding two of them adds their ranks, so a solver in a compressed format cannot keep what it produces. Every step is followed by a truncation — and whether that truncation is a floor on the residual depends on the right-hand side rather than on the truncation.