For #AdaLovelaceDay21, a long thread on Klári Dan von Neumann, writer of the first truly useful, complex programs ever to have been executed on a modern computer and to my mind, the most overlooked person in the history of computing 1/
Klári was born 110 years ago to a wealthy Jewish family in sparkling Belle Époque Budapest. The family hosted riotous parties where businessmen and politicians rubbed shoulders with artists and writers. She would rekindle the spirit of those gatherings in America years later 2/
Klári first met John von Neumann on the Riviera in Monte Carlo in the early 1930s. The Hungarian mathematical genius had a ‘system’. When he ran out of money, she bought him a drink. They were married in 1938. She was his second wife. He was her third husband 3/
The pair lived in a grand white clapboard house in Princeton, where von Neumann was a professor at the elite Institute for Advanced Study (along with Albert Einstein and Kurt Gödel) 4/
During the war, Klári, who had no education beyond high school, worked on demographic projections at the university’s Office of Population Research. She was quickly promoted and turned down an offer of an academic post at the university 5/
In the 1940s, bombs and computers were foremost in von Neumann’s mind. At Los Alamos (below), he helped design the ‘Fat Man’ atom bomb. In 1944, while looking for the fastest calculating machines in the US, von Neumann chanced upon the ENIAC... 6/
Soon to become one of the world’s first digital electronic computers, the room-filling ENIAC was not a modern ‘stored-program’ computer. Born as a machine of war, the ENIAC was made for a single purpose: calculating artillery trajectories 7/
After joining the project, von Neumann produced the EDVAC report, the blueprint for almost all computers today. In April 1947, faced with a huge backlog of bomb calculations from Los Alamos, von Neumann hit upon the idea of converting the ENIAC into a stored-program computer 8/
Los Alamos hired Klári as a consultant that summer. Coding, she said, was like a ‘very amusing and rather intricate jig-saw puzzle’. In April 1948, she and physicist Nicholas Metropolis converted the ENIAC into a stored-program computer – the first of millions more to come 9/
The first programs to run on the ENIAC in its new guise were written by Klári. They were Monte Carlo simulations, tracing the paths of neutrons through an atom bomb. The code listing was 28 pages long—all in Klári’s handwriting… /10
Time on the ENIAC was precious, and the team laboured all hours of the day and night to get the job done. Klári lost 15 lbs and needed check-ups at Princeton Hospital. Still, she wrote the definitive guide to the conversion and use of the ENIAC in its new mode /11
In October, Klári returned to the Ballistics Research Laboratory in Maryland for a second Monte Carlo run on the ENIAC. The run was finished on 7 November. Next month, she travelled solo to Los Alamos to defend her work before the likes of Edward Teller and Enrico Fermi /12
‘Things are kind of upside down,’ Klári wrote to family friends Stan and Françoise Ulam shortly before the third and final Monte Carlo run began. ‘Please pray for me and hope for the best.’ The problems were finished, successfully, on 24 June 1949 /13
Klári came home exhausted, reporting she had ‘brought with me to Princeton all secret documents’– probably nuclear cross-section data showing the chances of fission occurring in different materials. Los Alamos accorded that level of trust to very few-and even fewer women /14
In 1950, Klári returned to the Ballistics Research Laboratory one last time to test Teller’s ‘Super’ design. The simulations confirmed that Teller’s hydrogen bomb assembly would not work, and the project was abandoned. Modern bombs are based on the later Teller-Ulam design /15
After the Super calculations, Klári retired from the forefront of computing. Plagued by insecurity and worsening bouts of depression, she penned no further code herself, even when her husband’s machine at the IAS started running reliably in 1952 /16
The ‘Manchester Baby’, usually credited as being the world’s first electronic stored-program computer, ran its first program on 21 June 1948, two clear months 𝙖𝙛𝙩𝙚𝙧 Klári’s code ran on the reconfigured ENIAC, arguably also a stored-program computer /17
The Manchester Baby cycled through 17 instructions over fifty-two minutes to determine that the highest factor of 262,144 is 132,072. Klári’s 𝟖𝟎𝟎-command program, which ran two months earlier, was used to adjust the composition of atom bombs... /18
The invention of the closed subroutine is often credited to computer scientist David Wheeler, but Klári’s code made use of one at least a year earlier than he did, to generate random numbers by von Neumann’s ‘method of middle-squares’… 19/
Klári’s story ends tragically. She married a fourth time after von Neumann’s death but could not escape her ghosts. In November 1963, she filled her elegant black cocktail dress with 15 pounds of wet sand and walked into the sea off La Jolla 20/
The full scope of Klári’s contributions to computing have only recently come to light. Run on an ENIAC emulator today, her code reliably spits out the right numbers, plotting the fates of neutrons inside the atom bomb that her husband had helped build… 21/
Thanks for reading. There’s more about Klári Dan (including excerpts from her amazing memoirs) in my book about her third husband, John von Neumann out now in the UK and many other countries, US and Canada on 22 February...…

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More from @Ananyo

7 Oct
To celebrate, a bumper thread about the genius at the centre of my book. RT ░N░O░W░ to spread the word... and for a chance to WIN a signed copy (yes, I’ll post abroad if I need to) 1/…
This is the story of the 20th century’s foremost forgotten intellectual, a man who was in his day as well-known as Einstein—and considered smarter. Sixty-five years after his death, the impact of von Neumann’s ideas on contemporary life are...without parallel 2/
What did von Neumann do? His contributions to pure maths would fill several books and I’ve touched on some (eg. ergodic theorem, von Neumann algebras). But ‘The Man from the Future’ is really about unpicking one mathematician’s incredible impact on our lives today 3/
Read 16 tweets
25 Jan
I hate lockdowns and I hate schools being closed. Which is why I don't want a fourth lockdown later this year. How do we avoid that? 1/
First let's counter this idea that scientists are pessimistic. This isn't true. In my experience, generally, they're rather an optimistic bunch. My rule of thumb is that if you listen to many scientists, they're actually giving you an upbeat interpretation of the facts. 2/
Luckily, I left the lab 20 years ago and I'm a born glass half-empty kind of person. So let's look at where we are without rose-tinted glasses-and where we might be at the end of the year. Then you can decide what the government should do now. 3/
Read 21 tweets
6 Oct 20
Great series from @PhysicsWorld on scientists (nearly all women) overlooked for a Nobel. Additional reason that Meitner was overlooked: as a refugee in Sweden, she was working in Manne Siegbahn's lab... 1/
Siegbahn was a physics Nobelist, very influential in the higher echelons of Swedish science and, apparently, a notorious misogynist (see Ruth Lewin Sime's ace biog) who was resentful about Meitner's presence.
Sime's quarter-century old biography is a compelling portrait of Meitner's life-- including a record of the many many slights she endured during her life at the hands of some of her closest colleagues-slights we now commonly call microaggressions and gaslighting. 3/
Read 5 tweets
19 Apr 20
1/ Thread on Sweden, #coronavirus, the mathematician John von Neumann and the war that didn’t occur
2/ Von Neumann helped invent, among other things, the modern computer, game theory and the atom bomb. He predicted WWII, the Holocaust, that France would be overrun quickly, that the US would enter the war when UK struggled...
3/ One of his predictions, however, was that there would be a catastrophic nuclear war with the Soviet Union before 1950. He advocated pre-emptive war-a massive nuclear strike on Russia before it could get the bomb
Read 10 tweets
6 Apr 20
1/ Some thoughts on medium/long term 'exit strategy'. I can't see one without significant drawbacks if, as seems likely, relatively small proportion of population infected with #coronavirus. Very happy to be corrected. Possibilities...
2/ Option A: Slowly lift lockdown measures when peak has subsided eg send kids back to school, reopen shops - but continue social distancing. This will result in second wave of infections, which would have to be followed by another lockdown lasting weeks...
3/ ..There might have to be a third cycle of lockdowns before vaccine arrives. Given economic devastation caused by first lockdown, I can't see UK/US/EU governments going down this route.
Read 13 tweets
10 Jun 19
Fun #Boris fact. About 13 years ago, when I was news ed at @ResFortnight, we sent a reporter along to interview the then shadow higher education minister about universities and science policy. It was a total farce. He neither knew nor cared one jot....
@ResFortnight At one point, he blustered (approximately), "Well you clearly know more about this than I do, Why don't you tell me what our policies should be."
@ResFortnight Universities and research, I've always believed, are incredibly important-economically and socially. I was naive enough at the time to be shocked at such blatant disregard of the issues that I still regard as central to Britain's future.
Read 5 tweets

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