## a journal of the plague year [October reviews]

Posted in Books, Kids, Mountains, pictures, Travel with tags , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , on October 31, 2020 by xi'an

Read two more “little red” books from Éditions Guérin/Paulsen, the fantastic Chamonix editor, namely, Lénine à Chamonix by François Garde, a former Secretary-General of the Government of New-Caledonia, and Les Hallucinés (Un voyage dans les délires d’altitude), by Thomas Venin. The first book is a collection of short stories related to mountains, ranging from the realistic to the fantastic, and from good to terrible. I think in particular of the 1447 mètres story that involves a Holtanna like big wall in Iceland [good start then!], possibly the Latrabjarg cliff—although it stands at 1447 feet, not meters!, and the absurd impact of prime numbers on the failure of the climbing team. Lénine à Chamonix muses on the supposed day Vladimir Illitch “Lenin” Ulyanov spent in Chamonix in 1903, almost losing his life but adopting his alias there [which clashes with its 1902 first occurrence in publications!]. The second book is about high altitude hallucinations as told by survivors from the “death zone”. Induced by hypoxia, they lead hymalayists to see imaginary things or persons, sometimes to act against their own interest and often to die as a result. The stories are about those who survived and told about their visions. They reminded me of Abele Blanc telling us of facing the simultaneous hallucinations of two (!) partners during an attempt at Annapurna and managing to bring down one of the climbers, with the other managing on its own after a minor fall resetting his brain to the real world. Touching the limits of human abilities and the mysterious working of the brain…

Cooked several dishes suggested by the New York Times (!), including a spinach risotto [good], orecchiette with fennel and sausages [great], and malai broccoli [not so great], as well as by the Guardian’s Yotam Ottolenghi’s recipes, like a yummy spinash-potatoe pie. As Fall is seeping in, went back to old classics like red cabbage Flemish style. And butternut soups, starting with our own. And a pumpkin biryani!

Read Peter Hamilton’s Salvation, with a certain reluctance to proceed as I found the stories within mostly disconnected and of limited interest. (This came obviously as a disappointment, having enjoyed a lot Great North Road.) Unlikely I read the following volumes in the series. On the side, I heard that fantasy writer Terry Goodkind died on Sept. 17. He had written “The Sword of Truth” series, of which I read the first three volumes. (Out of 21 total!!!) While there were some qualities in the story, the setting was quite naïve (in the usual trope of an evil powerful character that need be fought at all costs) and the books carry a strong component of political conservatism as well as extensive sections of sadistic scenes

Watched Tim Burton’s 2012 Dark Shadows (terrible!) and a Taiwanese 2018 dark comedy entitled Dear Ex (誰先愛上他的) which I found rather interesting and quite original, despite the overdone antics of the mother. I even tried Tim Burton’s Sweeney Todd for a few minutes, being completely unaware this was a musical!

## first 8000

Posted in Mountains with tags , , , , , , , , , , , , , on June 3, 2020 by xi'an

## Ueli Steck dies on Nupse [Ueli Steck tödlich verunglückt]

Posted in Books, Mountains, Running with tags , , , , , , , on April 30, 2017 by xi'an

Ueli Steck was a Swiss climber renowned for breaking speed records on the hardest routes of the Alps. Including the legendary Eigerwand. And having been evacuated under death threats from the Everest base camp two years ago. I have been following on Instagram his preparation for another speed attempt at Everest the past weeks and it is a hug shock to learn he fell to his death on Nupse yesterday. Total respect to this immense Extrembergsteiger, who has now joined the sad cenacle of top climbers who did not make it back…

## optimal Bernoulli factory

Posted in Statistics with tags , , , , , , , , , , on January 17, 2017 by xi'an

One of the last arXivals of the year was this paper by Luis Mendo on an optimal algorithm for Bernoulli factory (or Lovàsz‘s or yet Basu‘s) problems, i.e., for producing an unbiased estimate of f(p), 0<p<1, from an unrestricted number of Bernoulli trials with probability p of heads. (See, e.g., Mark Huber’s recent book for background.) This paper drove me to read an older 1999 unpublished document by Wästlund, unpublished because of the overlap with Keane and O’Brien (1994). One interesting gem in this document is that Wästlund produces a Bernoulli factory for the function f(p)=√p, which is not of considerable interest per se, but which was proposed to me as a puzzle by Professor Sinha during my visit to the Department of Statistics at the University of Calcutta. Based on his 1979 paper with P.K. Banerjee. The algorithm is based on a stopping rule N: throw a fair coin until the number of heads n+1 is greater than the number of tails n. The event N=2n+1 occurs with probability

${2n \choose n} \big/ 2^{2n+1}$

[Using a biased coin with probability p to simulate a fair coin is straightforward.] Then flip the original coin n+1 times and produce a result of 1 if at least one toss gives heads. This happens with probability √p.

Mendo generalises Wästlund‘s algorithm to functions expressed as a power series in (1-p)

$f(p)=1-\sum_{i=1}^\infty c_i(1-p)^i$

with the sum of the weights being equal to one. This means proceeding through Bernoulli B(p) generations until one realisation is one or a probability

$c_i\big/1-\sum_{j=1}^{i-1}c_j$

event occurs [which can be derived from a Bernoulli B(p) sequence]. Furthermore, this version achieves asymptotic optimality in the number of tosses, thanks to a form of Cramer-Rao lower bound. (Which makes yet another connection with Kolkata!)

## कञ्चनजङ्घा [jatp]

Posted in Statistics with tags , , , , , , , , , , , on January 1, 2017 by xi'an