Part I ended in January 2009 with a $10,000
cheque decoded in an hour and a puzzle that had survived its first deadline
untouched. Part II covers everything since: the contest's slow death, the
decade in which one number, 467, refused to move, the day the archive
itself nearly vanished, and the record wave that finally moved it. As
before, this is the community's story told from the
eternity2 archive, and every event links to
the message where it happened.
The Hungarian "we solved it" rumor that part I left hanging died the way
such claims always die on this list. Once properly translated (a team at
ELTE university claiming a full solve via an algorithm salad that included
alpha-beta pruning, for a one-player puzzle), the native speakers called the
posts confused and the engineers ran the arithmetic
(msg 6575). By June the
claimant's account and every comment had been deleted from the Hungarian
forum (msg 6764).
The verified story of 2009 was quieter and better. JSA ran Louis Verhaard's
public eii solver on a single PC
and logged the climb: four million 463s, 625 466s, and finally, at day ~82,
a 467, independently reproducing the prize score with the public binary and
quantifying just how thin the air gets above 466
(msg 6687). In
August, Verhaard himself gave the definitive first-person account of the
winning entry: "Anna is my wife"; she submitted it, "it was my program that
did the job", and the 467 board contained 247 flawless pieces
(msg 6891). That December he
disclosed the method part I could only hint at: he had found 467 "more than
50 times", by letting the backtracker place one mismatching edge at chosen
depths, the move known as
edge slipping, gated by depth
(msg 7321).
The second scrutiny date, 31 December 2009, replayed the first as farce
minus the payout. Weeks of silence, then a news item ("Eternity II remains
unsolved") with no winner and, unlike 2008, no best-partial prize at all
(msg 7471). A member extracted
a written Q&A from Tomy: no organised activity in 2009, partial solutions
were not even scored, and "the year one prize was part of the initial
promotion only" (msg 7488).
Verhaard confirmed he had not improved on his 467
(msg 7494). He also
republished his solver at shortestpath.se, its long-term home, after his
band's website folded
(msg 7439,
msg 7446).
Claims bloomed in the vacuum anyway: an E2Lab popup announcing a 471 on a
board that was never saved
(msg 7284), a hand-solve
implying at least 472, dismissed on sight
(msg 7383,
msg 7427). Neither produced a
board. Meanwhile Eternity I veteran doc_s_smith returned after three years
and turned the list into an algorithms workshop
(msg 7755), framing the
target the era could realistically chase: solving E2 itself being hopeless,
"the challenge is clear: beat 468 matching edges"
(msg 7803). When his
Monte-Carlo estimator disagreed with Brendan Owen's
complexity model by five
orders of magnitude, Verhaard defended the model as "the finest work that
has ever been published about E2"
(msg 7810), a sentence the
next fifteen years would keep proving right.
Asked for a one-year extension of the final scrutiny date, Tomy answered in
one line: "No decsions [sic] will be made until the next scrutiny date"
(msg 8006). The deadline of
31 December 2010 passed in gallows humour, with members joking about
couriering a hypothetical last-minute solution to the post office
(msg 8197). Then the official
site went dark, "suspended pending final scrutiny confirmation"
(msg 8270); Verhaard posted
"I can honestly tell you that I didn't solve it"
(msg 8277).
The end arrived via France: a Tomy France press release (deadline passed,
no winner, no additional year, the $2M unclaimed) met with disbelief until
the source URL surfaced and the English page followed two days later
(msg 8339,
msg 8373). Monckton's emailed
reply to a member closed the door in person: the competition was over, and
"Extension of time is not allowed under the rules", rules which, members
immediately pointed out, explicitly allowed further scrutiny dates at the
promoter's discretion
(msg 8477,
msg 8478). Brendan Owen, the
man who had been posting since before the puzzle launched, said goodbye: "It
was great fun". He also asked Verhaard to congratulate his wife on the
highest score, first-party confirmation that 467 stood at the contest's
close (msg 8429).
Two loose ends defined the aftermath. One was the claim vacuum: a member's
476 without the hint (the original message is missing from the archive;
it survives through its replies,
msg 8247) escalated into
multiple hintless-480 claims and met the community's zero-knowledge wall
(Owen: publish the grid of piece ids); nothing was ever published
(msg 8676). The other was the
solution itself. The group owner laid out the custody arrangement: nobody,
not Tomy, not Monckton, knows the solution; it sits with independent loss
adjusters (msg 8502). Owen
then gave the statement still quoted today: Alex Selby and Oliver Riordan
created a solution when Monckton paid them to generate a practically
impossible puzzle, and it lies "hidden amongst reams of printed text which
is locked in a safe" as insurance against legal challenge
(msg 8823). In April 2011 the
official site confirmed the prize had gone unclaimed
(msg 8846).
What replaced the money was a ladder. Community leaderboards appeared in the
group database (msg 8222,
msg 8735); Owen, prompted by a
golden-ratio guess, proved that a backtracker's node counts peak at fraction
(1 − 1/e) of the board: 256 × 0.632 = 161.8, the closed form behind the
long-observed "magic of 161"
(msg 8125); and the first
exhaustive searches of Owen's
9×9 benchmarks landed within an order of
magnitude of his theory's predictions
(msg 8793,
msg 8803). A new name did most
of that checking: Peter McGavin, who by 2011 was running the list's
complex-theory service desk and had computed the numbers that became
canon, about 14,702 expected solutions with the mandatory piece placed
(msg 8924).
Three full years, 2012 to 2014, produced fewer messages than a busy
quarter of 2008. Academia arrived in person: Tony Wauters posted his group's
peer-reviewed hyper-heuristic paper (best score 461/480 in an hour) and
stayed to answer questions
(msg 9017); a second paper,
on MILP and Max-Clique heuristics, followed in 2017
(msg 9683). The only prize
money of the era was a Czech retailer's 12,000 EUR re-run of the contest
(msg 9072), extended to July
2015 (msg 9271); its expiry
then passed without a single mention on the list. When newcomer Dima asked
for the best known result in late 2014 and got the canonical answer, his
reply was the era in one line: "467 still, really? But that was 6 years
ago!" (msg 9318).
Under the surface, two things matured. Theory became a document: McGavin
transcribed Owen's complexity model into LaTeX as complex_theory.pdf, in
the group's files (msg 9188),
turning folklore into something newcomers could actually read. And speed
became a culture again: Arnaud Carré posted a 114 million recursions per
second single-core solver as a comparison standard
(msg 9233), Michael Field
designed an FPGA backtracker
(msg 9226), and a
nodes-per-watt ledger ran from Raspberry Pi clusters to an Xbox One X
(msg 9519,
msg 9816). The claim-filter
kept working too: a 2014 "eternity2 resolved ;)" died when verification
found one piece used five times
(msg 9286,
msg 9301).
Then, in September 2017, the community's shared benchmark fell. Peter
McGavin found the first new solution to Brendan Owen's hint-free 10×10,
the "monster" that had resisted everyone since 2008, by industrialising
exactly what the list had converged on: enumerate the ~20 million possible
first rows, rank them by complex theory's chance-of-solution per node, and
farm them to every core available, from home ODROIDs and $12 Orange Pis to
borrowed work servers, 400+ cores in all
(msg 9686,
msg 9688). The solution cost
about 2×10^17 nodes (roughly 180 core-years) and arrived on row-search
~92,907 against a predicted one-per-70,000, inside the theory's error bars:
in McGavin's words, "no new methods, just systematic persistence and the
law of large numbers". John Gilbert spoke for the list: "Amazing that it is
being truly just as hard as predicted"
(msg 9693). It was the
strongest validation Owen's theory ever received, and the proof that the
benchmark culture, not the record chase, had been the group's real
achievement of the decade.
The same thread raised a records question that never resolved: Dima
surfaced a 2009 tweet by TopCoder star Naohiro Takahashi claiming a 468,
never accompanied by a board, possibly scored under different contest rules,
and left permanently unverified
(msg 9694,
msg 9697). Two months later
McGavin placed all 256 real pieces on the 16×16 board with all 480 internal
joins matched, an "unframed E2" with gray edges buried in the interior, and
was scrupulously precise that it was not a solution to the puzzle
(msg 9736,
msg 9750,
msg 9757). The window closed
at low ebb: 2018 produced 42 messages, and to a newcomer's poll a veteran
answered, "anybody still crunching with backtracking ?? no way...."
(msg 9832).
In October 2019 Yahoo announced it would erase all Groups content within
weeks: twelve years of piece counts, proofs, debunkings and solver source,
gone. Jef Bucas raised the alarm
(msg 9920), Robert Gerbicz
proposed groups.io, founder Ole Knudsen created the new group, and JSA paid
the transfer fee: "I can pay for the first 5 years"
(msg 2). The automated transfer
completed on 8 November 2019 with roughly 2,000 members, messages, files and
photos intact (msg 9934,
msg 9937). The
archive this chronicle is written from survived by days.
Two weeks later, Bucas launched the other half of the modern era's
infrastructure: e2.bucas.name, a board viewer whose
boards live entirely in the URL (nothing is transmitted to the server),
with a drop-down of best boards that quietly became the community's record
book (msg 9955). Fittingly,
the year's records news was archival too: Verhaard confirmed his
astonishing 249-piece flawless partial was real, "no cheating… found it
after a week or so, on 1 computer"
(msg 9890).
On 31 August 2020, a member relayed a Reddit post: a new best board with
only 12 breaks, 468/480, the first advance past Verhaard's 467 in twelve
years (msg 10032). The author
was Joshua Blackwood, a complete outsider unknown to the list. Bucas
verified the board, added it to the viewer, and passed on the detail that
made veterans sit up: the author "says he can find a 468 every 4 days!"
(msg 10033). Three days later
Blackwood open-sourced the solver itself, carrying heuristic changes he
believed made it "twice as good" and pre-configured to hunt 469s
(msg 10037). His engineering
notes were as valuable as the code: SAT solvers, GPUs and pre-solved 2×2
caches had all been measured and discarded; the magic was the heuristic
schedule and a small set of allowed "break" depths
(msg 10056,
msg 10076).
The community did what it does with good code: it ran it. On 9 September
2020, Peter McGavin, the man who had solved the 10×10, posted: "Your
solver is fantastic!! I ran it for a few days on about a couple of hundred
cores and hit the jackpot. New record score of 469! Only 11 breaks!"
(msg 10045). Bucas rewrote
the solver in C, roughly doubling its speed, and a wave of further 469s
followed through November
(msg 10065,
msg 10067); the generator
behind the port was published as libblackwood
(msg 10078). Then, on
30 March 2021, a two-line message: the URL of a 470/480 board
(msg 10117). Blackwood later
confirmed the public repo was "the exact code used to find a 470"
(msg 10161), then retired: "I
have not written a line of code or run any algorithms since I found a 470"
(msg 10185).
One clarification matters for how these records are read. The contest's own
rules pinned only the starter piece, required at its specified location
and rotation; the four other clues were optional aids
(msg 11046). Every record
board from the 468 up sits in that same starter-only regime: piece 139 at
its mandatory square, none of the four optional clues at their official
positions, a claim verified at board level for the 470
(msg 10554). The 470 is the
same puzzle as the 469s long quoted as the ceiling, not an easier variant;
Blackwood had the clue tiles and "deliberately didn't use" them
(msg 10185). Boards that also
honour the four optional clues are a separate, stricter ladder (more on it
below). The records page keeps the two regimes
explicitly apart.
Blackwood allowed himself one encore: reconfiguring his solver for zero
breaks, he pushed the consecutive-placement record from Verhaard's
long-standing 226 to 227, then 230, all on "a single PC in my basement"
(msg 10536,
msg 10544,
msg 10547).
The post-wave years settled into a rhythm of invariants, calibration and
provenance. In May 2022 Al Hopfer, a regular since 2009, stated the
border condition now known on this site as the
NS-1 balance: the outer rim
of the 14×14 interior "must have the same mixture (parity) of the internal
images on all the 56 border pieces"
(msg 10754,
msg 10757). In the same
thread, Carlos Fernandez was solving 14×14 quadrants in about four minutes
(msg 10802). Big interior
blocks had become routine; closing the frame had not. The 2008 prize score,
meanwhile, was formally demoted to a regression test: "last week I found
about 30 x 467. I use this target to calibrate the code I'm running",
wrote Bucas (msg 11001).
The stricter ladder got its own record. A 2023 thread collecting bests that
respect all five clue placements climbed from 412 through 452 and 458
to Bruno Gauthier's 460 (msg 11074),
which held for over three years until Benjamin Riotte's 464 in July 2026, a
461 rising to 464/480 with his own modified-Blackwood solver, with Igor Pejic
reaching the same 463–464 range independently
(groups.io). The
same year produced the era's canonical false positive: a complete,
480-matching 16×16 built by McGavin from pieces of one E2 set, one Clue-1
set and one Clue-2 set, a "480" that is not the puzzle, posted precisely
to make that point
(msg 11169).
Theory completed its long journey from posts to source code. In January
2024 McGavin restated the headline numbers: 14,702 expected solutions with
just the starter, 0.00000004 with all five hints, "very strongly
suggesting… a single, unique solution"
(msg 11193). The next
day he published complex_theory.c, his exact C implementation of Owen's
model (msg 11197): the
reference this site's own
complexity engine
ports. In December, Bucas tied the record: "I restarted a few threads of
Joshua's code, and… another 470 appeared!"
(msg 11401), with Fernandez
posting a border-rearranged variation the same week
(msg 11403). Bucas's
crediting never wavered: "Joshua Blackwood is the current record holder. I humbly used his code"
(msg 11555). And his
wrapper_blackwood project put the point beyond opinion: a farm that varied
every parameter of Blackwood's algorithm and measured the results,
concluding that within the swept parameters the author's manual tuning was
already near-optimal; his notes
are published on this site with his explicit permission
(msg 11905).
And the founders came back, or didn't. In May 2025, Brendan Owen posted
for the first time in roughly fourteen years, answering a newcomer's
difficulty question (msg 11500),
telling McGavin his years of work were "very impressive"
(msg 11521), and returning to
his own model with a refined calculation of edge-join probabilities
(msg 11546). The AI era
arrived first as farce: ChatGPT confidently informing a member that a
solution "was eventually found by a team of puzzle enthusiasts"
(msg 10993), then a
vibe-coded solver app whose owner conceded "it isn't 100% guarantee because
Base44 is AI", met with patient tutoring rather than ridicule
(msg 11755,
msg 11818). And in February
2026, the annual welcome note opened with a tribute to Kronjuvel: Ole
Knudsen, who created the group, ran it for the better part of two decades,
and has been missing from the list since 2023
(msg 11771).
The archive's current edge is 31 March 2026: a SAT thread still arguing
about 4 GB CNF encodings, a standing just-for-fun challenge to invalidate a
border partial, and one member's line for the anniversary: "slowly we are
progressing to 20 years of E2 next year ;-) Will we solve E2 in 2026...?"
(msg 11820,
msg 11823). The ledger after
nineteen years: the 480 has never been found; the 470 has stood since 2021;
and the ten missing edges are, as ever, where the whole problem
lives.