# Who's who of E2 research

> Two decades of Eternity II research were done by named people on a mailing list. This page is the gallery: who they are, what each of them contributed, and where to read it in their own words. A thank-you as much as an index.

- Canonical page (with interactive figures/demos): https://eternity2.dev/research/people/
- Updated: 2026-07-02
- Source: Brendan Owen derives the 17+5 design as the hardest possible puzzle (groups.io message 1947) — https://groups.io/g/eternity2/message/1947
- Source: Louis Verhaard's first-person account of the 467: “it was my program that did the job” (groups.io message 6891) — https://groups.io/g/eternity2/message/6891
- Source: Peter McGavin solves Brendan Owen's 10×10 benchmark (groups.io message 9686) — https://groups.io/g/eternity2/message/9686
- Source: Joshua Blackwood's 470, the standing record (groups.io message 10117) — https://groups.io/g/eternity2/message/10117
- Source: Al Hopfer states the NS-1 border balance (groups.io message 10754) — https://groups.io/g/eternity2/message/10754
- Source: Brendan Owen returns to the list after fourteen years (groups.io message 11500) — https://groups.io/g/eternity2/message/11500

---
The [history pages](/research/community/hunt) tell the community's story in
order; this page tells it by person. Nearly everything this wiki knows
(every record, theory, tool and
[documented dead end](/research/build/dead-ends)) traces back to someone who
posted it on the [eternity2 mailing list](https://groups.io/g/eternity2),
usually for free, often for years. Consider this gallery an index and a
thank-you at the same time. Names appear as people signed their public
posts; every claim links to a message.

Many of the people below have their own contributor page: a name in **bold
with a link** opens it, gathering their profile, their sourced posts, and any
pages they have written here. [Raphaël Anjou](/research/people/raphael-anjou),
who maintains the wiki and runs the lab experiments, has one too, one
researcher among the others. The names without a link are documented right
here, on this page.

## The founders and launch analysts (2000–2007)

### [Brendan Owen](/research/people/brendan-owen)

The founder. Owen created the eternity_two group in October 2000, six and a
half years before the puzzle existed
([msg 384](https://groups.io/g/eternity2/message/384)), and set its
scientific tone: within two days of the January 2007 announcement he had
derived the expected-solutions formula that makes difficulty a design
parameter ([msg 38](https://groups.io/g/eternity2/message/38)), and on
launch weekend he digitized the real pieces and published the first
solution-count estimate
([msg 987](https://groups.io/g/eternity2/message/987)). His signature
results: the proof that a 17+5 colour split is the hardest possible 16×16
([msg 1947](https://groups.io/g/eternity2/message/1947)), the exact
search-tree model now called
[complex theory](/research/why/complex-theory)
([msg 5197](https://groups.io/g/eternity2/message/5197),
[msg 5209](https://groups.io/g/eternity2/message/5209)), the 9×9/10×10
[benchmark puzzles](/research/build/benchmarks) the community still races
on, and the closed-form
peak-depth proof 256 × (1 − 1/e)
([msg 8125](https://groups.io/g/eternity2/message/8125)). After a farewell
at the contest's close
([msg 8429](https://groups.io/g/eternity2/message/8429)) he returned in
2025, refining his own model
([msg 11500](https://groups.io/g/eternity2/message/11500),
[msg 11546](https://groups.io/g/eternity2/message/11546)).

### [Günter Stertenbrink](/research/people/gunter-stertenbrink)

An Eternity I veteran and the group's earliest provocateur of estimates: in
2001 he asked, years ahead of the fact, how one would design a puzzle with a
huge prize and only a ~1% chance of being solved in ten years
([msg 15](https://groups.io/g/eternity2/message/15)), and he greeted the
2005 press claims with "So we can conclude, the end of the universe is in
several years." ([msg 34](https://groups.io/g/eternity2/message/34)). For
two decades he checked the list's numbers, from exact-cover conversions in
2007 to the nodes-per-watt hardware ledger of the 2010s.

### [Dave Clark](/research/people/dave-clark)

Author of the distributed Eternity I solver ESolve, he rejoined in 2001
([msg 21](https://groups.io/g/eternity2/message/21)) and built eternity2.net,
the BOINC project that was the community's public face in 2007
([msg 756](https://groups.io/g/eternity2/message/756)). He shut it down with
full accounting: 1.6 TFlops, over 10^19 operations, no solution
([msg 3511](https://groups.io/g/eternity2/message/3511)). He open-sourced
his solver ([msg 3716](https://groups.io/g/eternity2/message/3716)) and left
the archive its best primary source on the puzzle's creation: his phone call
with Monckton describing how the solution was generated and vaulted
([msg 4177](https://groups.io/g/eternity2/message/4177)).

### Txibilis

Angel de Vicente, who signed Txibilis, built the standard suite of E2-like
benchmark boards ([msg 1886](https://groups.io/g/eternity2/message/1886))
and was the community's best hand-designer of
[fill orders](/research/build/backtracking/fill-order). His duel with
doc_s_smith's automated optimizer drove full-search node counts down by
orders of magnitude
([msg 2928](https://groups.io/g/eternity2/message/2928)). The benchmark
culture that later validated complex theory starts with him.

### doc_s_smith

Mid-duel, the list discovered who doc_s_smith was: Dietmar Wolz, finder of
most of the known Eternity I solutions
([msg 2972](https://groups.io/g/eternity2/message/2972)). His automated
strategy optimizer set benchmark records in 2007
([msg 2896](https://groups.io/g/eternity2/message/2896)); returning in 2010
he published a Java toolbox that turned the list into an algorithms workshop
([msg 7755](https://groups.io/g/eternity2/message/7755)) and gave the
post-contest era its working goal: "beat 468 matching edges"
([msg 7803](https://groups.io/g/eternity2/message/7803)).

### kubzpa

Author of the first serious solution-count paper, putting E2 near 15 million
solutions ([msg 3497](https://groups.io/g/eternity2/message/3497)), and of
the era's cleanest impossibility result: the parity argument that no board can
score exactly 479 by its interior seams
([msg 1640](https://groups.io/g/eternity2/message/1640)). It held for seventeen
months, until Verhaard pointed out the one loophole
([msg 6317](https://groups.io/g/eternity2/message/6317)): flip a border piece
whose two outward border edges share a colour, and the board reads as 479 while
those unscored rim edges go untouched. That is a technicality of the unscored
border, not a break in the interior-parity math, which still holds, as Verhaard
himself noted that 479 "cannot be achieved in another way"
([msg 6319](https://groups.io/g/eternity2/message/6319)).

### mjqxxxx

Michael Quist was the list's mathematical referee. He posted the first fully
rigorous counting framework for E2-like puzzles
([msg 1221](https://groups.io/g/eternity2/message/1221)), sharpened the
border-balance theory
([msg 2098](https://groups.io/g/eternity2/message/2098)), and his reviews
caught the flaws that made others' results solid. Kubzpa amended his
solution-count paper after his pass caught a flawed Monte Carlo run
([msg 3589](https://groups.io/g/eternity2/message/3589)).

## The prize years (2007–2010)

### [Louis Verhaard](/research/people/louis-verhaard)

The only person the puzzle ever paid. His eii solver, released publicly
"because I am stuck"
([msg 5940](https://groups.io/g/eternity2/message/5940)), found the 467
that won the $10,000 scrutiny prize, entered under the name of his wife,
Anna Karlsson, as he confirmed himself: "Anna is my wife… it was my program
that did the job"
([msg 6349](https://groups.io/g/eternity2/message/6349),
[msg 6891](https://groups.io/g/eternity2/message/6891),
[msg 7451](https://groups.io/g/eternity2/message/7451)). His methods became
canon: comb-search fill orders
([msg 6112](https://groups.io/g/eternity2/message/6112)) and depth-gated
edge slipping ([msg 7321](https://groups.io/g/eternity2/message/7321)). He
was also complex theory's staunchest defender: "the finest work that has
ever been published about E2"
([msg 7810](https://groups.io/g/eternity2/message/7810)), and his 467 stood
for twelve years.

### Yannick Kirschhoffer

Author of the Eternity II Editor, the cross-platform Java editor and solver
GUI released in February 2008
([msg 4544](https://groups.io/g/eternity2/message/4544)) that became the
community's standard board tool for years. He was still offering help with
its code when it resurfaced in 2012
([msg 9064](https://groups.io/g/eternity2/message/9064)).

### Fred

Posting as Eternity Blogger, Fred built E2Lab in a burst of near-daily
releases in autumn 2009 ([msg 7148](https://groups.io/g/eternity2/message/7148)),
an editor/solver whose deliberate removal of its own "magic button", "to
respect the game rules", says a lot about the list's ethics
([msg 7150](https://groups.io/g/eternity2/message/7150)). His blog hosted
the community's tables through the post-contest years.

### [Al Hopfer](/research/people/al-hopfer)

A regular since 2008 and the community's border theorist. His "balance
doctrine" for puzzle generation appears in 2009
([msg 6842](https://groups.io/g/eternity2/message/6842),
[msg 6844](https://groups.io/g/eternity2/message/6844)); in 2022 he stated
the exact condition this wiki calls the
[NS-1 border balance](/research/why/border-balance)
([msg 10754](https://groups.io/g/eternity2/message/10754),
[msg 10757](https://groups.io/g/eternity2/message/10757)), and backed it
with a fully documented 222-piece partial with completed border
([msg 10862](https://groups.io/g/eternity2/message/10862)).

## The long decade (2010–2019)

### [Peter McGavin](/research/people/peter-mcgavin)

The era's anchor, and arguably the puzzle's most consequential researcher
after Owen. His work has [its own page](/research/lab/experiments/peter-mcgavin/backtracker).
He computed the canonical ~14,702 expected solutions
([msg 8924](https://groups.io/g/eternity2/message/8924)), transcribed
complex theory into LaTeX
([msg 9188](https://groups.io/g/eternity2/message/9188)) and later into
exact C code ([msg 11197](https://groups.io/g/eternity2/message/11197)),
which this site ports. In 2017 he solved Owen's hint-free 10×10 in ~180
core-years, inside the theory's error bars, its strongest validation ever
([msg 9686](https://groups.io/g/eternity2/message/9686),
[msg 9688](https://groups.io/g/eternity2/message/9688)), and in 2020 he
held the record himself: "New record score of 469! Only 11 breaks!"
([msg 10045](https://groups.io/g/eternity2/message/10045)).

### Tony Wauters

Academia in person. He posted his group's peer-reviewed hyper-heuristic
paper (461/480 in an hour) and stayed to answer questions
([msg 9017](https://groups.io/g/eternity2/message/9017),
[msg 9023](https://groups.io/g/eternity2/message/9023)), and his group
followed with the 2017 MILP and Max-Clique work
([msg 9683](https://groups.io/g/eternity2/message/9683)).

### Michael Field

A fastest-solver veteran of the early years who became the group's hardware
realist: his FPGA backtracker design projected ~5G placements per second per
chip ([msg 9226](https://groups.io/g/eternity2/message/9226)), and his
capacity analyses of GPU and FPGA routes told the list what silicon could
and could not buy ([msg 9003](https://groups.io/g/eternity2/message/9003)).

### Arnaud Carré

Arrived in 2009 and reset the speed standard in 2014 with a 114.5 million
recursions per second single-core solver offered as a comparison baseline
([msg 9233](https://groups.io/g/eternity2/message/9233)), returning in 2018
for the benchmark races.

### Adam Miles

The GPU flank. Arriving in 2017, he moved from CPU bit-tricks to a DirectX
12 compute solver running on an Xbox One X
([msg 9811](https://groups.io/g/eternity2/message/9811)) and re-verified
Owen's 9×9 set 1 exhaustively on GPU: the same 2 solutions as the 2014 CPU
census, in 25.4 hours
([msg 9822](https://groups.io/g/eternity2/message/9822)).

### JSA

The community's verifier and, later, its rescuer. In 2009 he reproduced the
467 with Verhaard's public solver, ~82 days on one PC, logging exactly how
thin the air gets above 466
([msg 6687](https://groups.io/g/eternity2/message/6687)). When Yahoo
announced it would erase the archive in 2019, JSA paid the groups.io
transfer fee, offering "I can pay for the first 5 years"
([msg 2](https://groups.io/g/eternity2/message/2)), and he still writes the
group's welcome notes
([msg 11771](https://groups.io/g/eternity2/message/11771)).

### Ole Knudsen

Kronjuvel (Kron) was there from the earliest years, retro-claimed a
231-piece partial from October 2007
([msg 7563](https://groups.io/g/eternity2/message/7563)), and as group owner
created the new groups.io home during the 2019 migration. The 2026 welcome
note opens with a tribute to him; he has been missing from the list since
2023 ([msg 11771](https://groups.io/g/eternity2/message/11771)).

## The record wave and the modern era (2019–2026)

### [Joshua Blackwood](/research/people/joshua-blackwood)

The outsider who ended the twelve-year freeze. Unknown to the list, he
announced a 468 on Reddit in August 2020
([msg 10032](https://groups.io/g/eternity2/message/10032)), open-sourced his
solver days later ([msg 10037](https://groups.io/g/eternity2/message/10037))
along with rare negative results (SAT, GPU and 2×2 caches all measured and
discarded, [msg 10056](https://groups.io/g/eternity2/message/10056)), and
in March 2021 posted the 470 that still stands
([msg 10117](https://groups.io/g/eternity2/message/10117)), found with the
exact public code ([msg 10161](https://groups.io/g/eternity2/message/10161)).
His algorithm is [decoded on this wiki](/research/lab/experiments/joshua-blackwood/solver).

### [Jef Bucas](/research/people/jef-bucas)

The modern era's infrastructure. He raised the alarm that triggered the
archive migration ([msg 9920](https://groups.io/g/eternity2/message/9920)),
built the [e2.bucas.name](https://e2.bucas.name) board viewer that became
the community's record book
([msg 9955](https://groups.io/g/eternity2/message/9955)), rewrote
Blackwood's solver in C as libblackwood, roughly doubling its speed and
powering the November 2020 wave of 469s
([msg 10065](https://groups.io/g/eternity2/message/10065),
[msg 10078](https://groups.io/g/eternity2/message/10078),
[msg 10067](https://groups.io/g/eternity2/message/10067)), and tied the 470
in 2024 ([msg 11401](https://groups.io/g/eternity2/message/11401)), always
crediting Blackwood. His wrapper_blackwood parameter study is republished
[on this wiki](/research/lab/experiments/joshua-blackwood/solver) with his permission
([msg 11905](https://groups.io/g/eternity2/message/11905)).

### Carlos Fernandez

The board surgeon. He produced a 469 by a single-piece swap of McGavin's
record board ([msg 10074](https://groups.io/g/eternity2/message/10074)), a
border-rearranged 470 variant
([msg 11403](https://groups.io/g/eternity2/message/11403)), four-minute
14×14 quadrant solves
([msg 10802](https://groups.io/g/eternity2/message/10802)), and high rungs
of the five-clue ladder
([msg 11068](https://groups.io/g/eternity2/message/11068)).

### Bruno Gauthier

A speed veteran of the 2014 era whose Forth solver ran at 80–90 million
nodes per second ([msg 9265](https://groups.io/g/eternity2/message/9265)),
he held the strictest record on the books for over three years: 460/480 with
all five clue pieces at their official positions, from 2023
([msg 11074](https://groups.io/g/eternity2/message/11074)) until Benjamin
Riotte's 464 in July 2026.

### Benjamin Riotte

Holder of the strict five-clue record. In July 2026 he pushed the best board
respecting all five clue placements from Gauthier's long-standing 460 to
**464/480** (16 broken edges), with his own modified-Blackwood DFS
([groups.io](https://groups.io/g/eternity2/message/11919)). Igor Pejic
reached the same 463–464 range independently in the same thread. It was the
first movement on the strict-canonical line in over three years.

### [Marijn Heule](/research/people/marijn-heule)

The SAT world's contact point. In the long-running SAT thread, a
collaborator of Marijn Heule reported that Heule's group had re-implemented
and improved the encoding behind the 2008 SAT benchmark results
([msg 10969](https://groups.io/g/eternity2/message/10969)), the
state of the art of the exact-methods flank, which was still debating
4 GB CNF encodings on the archive's very last day
([msg 11822](https://groups.io/g/eternity2/message/11822)).

### [Raphaël Anjou](/research/people/raphael-anjou)

Maintains this wiki and runs the experiments catalogued in
[the lab](/research/lab); his write-ups gather on his
[contributor page](/research/people/raphael-anjou), one researcher among the
others.

### [William Millilaw](/research/people/william-millilaw)

Ran a dense two-week solver campaign in 2026, most of it recorded as
refutations of methods that do not crack the puzzle. Two of his findings sharpen
the ceiling: a replica freeze test, and a halo SAT-residual test showing the
record boards are strict local optima. We reproduced the second on the public
boards, and it lands on the
[rigidity wall](/research/why/rigidity-wall) alongside the integer-programming
proofs
([reproduction](https://github.com/raphael-anjou/eternity2/tree/main/research/topics/rigidity-sat-halo)).

### onesmallstep

Founded the community's Discord server in November 2021 and kept it alive
through the quiet years (reported on the community Discord, November 2021; no
public message link). A dedicated solver
in his own right (self-reported best around 466–467), he is also the reason
the wiki once mis-carried a "2025 470": a record *relay* misread as a
record *claim*, corrected here from the Discord archive itself.

### Reinout Annaert

The Discord era's methodical hunter: a self-reported best of 469, the
linear-run subculture (229- and 230-piece consecutive partials), and the man
who settled where the hint placements come from: "They directly come from
Tomy's Hint Puzzles" (reported on the community Discord, December 2024; no
public message link). On the mailing list he confirms storing solution figures
scoring above 467/480 ([msg 11549](https://groups.io/g/eternity2/message/11549)).
His suggestions also shaped this site's playground roadmap.

## And many more

No gallery this size is complete. Among the many who belong here: Alan
O'Donnell, who had the first working solver weeks after the announcement
([msg 64](https://groups.io/g/eternity2/message/64)); Max, Verhaard's
sparring partner in the run to 467, whose own best was 465
([msg 6348](https://groups.io/g/eternity2/message/6348)); istarinz, who
broke 558 million placements per second in 2008 and became the group's
exhaustive-search verification authority
([msg 6212](https://groups.io/g/eternity2/message/6212)); antminder, whose
assignment-repair hybrid averaged a 462 per day in 2008
([msg 5589](https://groups.io/g/eternity2/message/5589)); Pierre Schaus,
whose constraint-programming paper supplied that repair operator
([msg 5601](https://groups.io/g/eternity2/message/5601)); capiman26061973,
founder of the five-clue ladder
([msg 11037](https://groups.io/g/eternity2/message/11037)) and the
invalid-combination mining programme
([msg 7768](https://groups.io/g/eternity2/message/7768)); David Barr,
open-source GPU and browser solvers across a decade
([msg 9367](https://groups.io/g/eternity2/message/9367),
[msg 11121](https://groups.io/g/eternity2/message/11121)); Henk van der
Griendt, who found the prize announcement everyone else had missed
([msg 6337](https://groups.io/g/eternity2/message/6337)); and
juraj.pivovarov, the community's rapid-prototyping conscience
([msg 9411](https://groups.io/g/eternity2/message/9411)).

## Corrections welcome

This page will always be incomplete, and it may be wrong in places: a
misattributed result, a missing name, a preferred spelling. If any of it
concerns you or your work, please say so on the
[mailing list](https://groups.io/g/eternity2) or through the
[contribute page](/research/contribute): corrections land with the same
sourcing rules as everything else here, and credit is the whole point of
this page.

## Related

- [The hunt, a history (part I: 2000–2009)](https://eternity2.dev/research/community/hunt) — The community's story, from a mailing list founded seven years before the puzzle existed to the $10,000 scrutiny prize won under a borrowed name, with every event sourced to its original message. Part I of a growing chronicle.
- [The hunt, a history, part II: 2009–2026](https://eternity2.dev/research/community/hunt-part-2) — Seventeen years after the prize: the contest dies with its solution locked in a safe, 467 stands for a decade, the archive survives Yahoo's shutdown by days, and then an outsider from Reddit rewrites the record book. Every event sourced to its original message.
- [Records & solvers](https://eternity2.dev/research/records) — Eternity II has never been solved, but fifteen years of community effort have pushed the best board to 470/480. Who holds what, how they did it, and why some headline "480" boards are not actually the real puzzle.