Chord steps per member of a drifting sequence, with the factorisation rebuilt every 4
At its defaults it draws chord steps per member of a drifting sequence, with the factorisation rebuilt every 4. Each point is one member of a continuation, warm-started from the previous member's answer and solved with a factorisation that is between zero and 3 members old. The lower series is the same sequence with a fresh factorisation at every member, which costs 6 to 5 steps throughout. The kept run costs 6 steps on a fresh factor and 12 at its worst, for 5 factorisations against 20.
staleness-trail is one function in lib/figures/reuse.js —
reuse — what a kept factorisation or preconditioner is worth, and for how long. 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 is one member of a continuation, warm-started from the previous member's answer and solved with a factorisation that is between zero and 3 members old. The lower series is the same sequence with a fresh factorisation at every member, which costs 6 to 5 steps throughout. The kept run costs 6 steps on a fresh factor and 12 at its worst, for 5 factorisations against 20.
refresh: 4
The arguments are the ones A factorisation kept past its date passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
Each point is one member of a continuation, warm-started from the previous member's answer and solved with a factorisation that is between zero and 3 members old. The lower series is the same sequence with a fresh factorisation at every member, which costs 6 to 5 steps throughout. The kept run costs 6 steps on a fresh factor and 12 at its worst, for 5 factorisations against 20.
refresh: 6
The arguments are the ones The penalty for keeping it is a ratio passes. A value nobody placed would be a picture no essay asked for and no claim was ever checked against.
Each point is one member of a continuation, warm-started from the previous member's answer and solved with a factorisation that is between zero and 5 members old. The lower series is the same sequence with a fresh factorisation at every member, which costs 6 to 5 steps throughout. The kept run costs 6 steps on a fresh factor and 20 at its worst, for 4 factorisations against 20.
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.
8 distinct claims across 3 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 conditioning the SPD construction can hold
a factor kept for several members costs more at the end of its life than at the start
a refactorisation rule of one kind or the other
a refresh period inside the sweep
a size the dense factorisations are affordable at
and refactorising at every member is a sequence that converges throughout
matmul shapes agree
the sequence gets far enough to show the shape
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 factorisation kept past its date
One Cholesky factor can serve five members of a drifting sequence and save 44 per cent of the work. Kept for twenty it does not lose accuracy — it stops converging altogether. The optimum and the cliff are four members apart, both move with the drift, and a rule written in a ratio the iteration has already computed finds them without being told what the drift is.
When the problem arrives againThe penalty for keeping it is a ratio
A kept incomplete Cholesky costs 40 iterations against a rebuilt one's 10 on 64 unknowns, and 55 against 17 on 256. Across six grids the difference between the two rises by 27 per cent and the ratio between them falls by 19. Neither quantity is free of the problem's size, and the one a policy is paid in is the one that transfers worse.
Randomised, and the guarantee that changes kindThe sketch that is spent
Every other object a sequence carries has a shelf life. A random sketch has one use. Deflate what its first round found and apply it again, and it returns the zero matrix — 9.0·10⁻¹⁵ where the first round saw 2.62 — because the input has been made orthogonal to the very draw the guarantee is over.