The RSS feed of henrydashwood.com
Neural networks are universal function approximators. They can, with an infinite number of parameters and data, learn any function. In practice, we can structure our models to encode priors about the problem we are working on, significantly reducing its complexity. For instance, a convolutional neural network bakes in the assumption that local spatial patterns are important. Attention assumes that…
import LaborMarketDiagram from "@/components/blog_components/LaborMarketDiagram"; Introduction In the first post of this series, we saw that London has higher wages than Newcastle, but also higher costs. Workers migrate between cities until they're indifferent about where to live. Economists call this spatial equilibrium. In the second post , we modelled a single city. We showed why Putney is more…
Introduction In the last blog , we explained why London is more expensive than Newcastle. Workers move between cities until they're indifferent about where to live, creating spatial equilibrium. Here's a slightly different question: Why is Putney more expensive than Teddington? Both are in South West London. Both are affluent, safe, and famous for their "village" feel, riverside pubs, and green…
import MigrationStabilityViz from "@/components/blog_components/MigrationStabilityViz"; import PowerLawViz from "@/components/blog_components/PowerLawViz"; Introduction According to Glassdoor, the average base pay for a software engineer in London is £59,000 ^1 , while in Newcastle it is £40,000 ^2 . This engineer could move south and earn an extra £19,000 per year. But London is more expensive. A…
A sequel to California: the first three centuries When Junípero Serra blessed the ground at San Diego, he stood on a coastline glimpsed only by Manila galleons in living memory. The Spanish knew almost nothing of the hundreds of autonomous peoples whose territories they proposed to occupy. By 1850, California would be part of the United States. Within the span of one human lifetime, a chain of…
I don’t much like ORMs. They hide the interesting bits, make performance an afterthought, and couple migrations to application frameworks in ways that age badly. SQL is already a very good DSL. I prefer: Start from an empty schema; the schema is the API. Evolve it with migrations. Write queries in raw SQL. There are tools that then let you compile them into type safe functions in whatever language…
John Rawls and the death of Western Marxism Key stages in the decline of academic Marxism The Ballad of the White Horse Once again: Imports do not subtract from GDP Reflections on Palantir Do we ever get over things? I appreciated this The World Bank and other IFIs should get serious about climate adaptation in low-income countries The Compliance Doom Loop The Curious Case of Colony Ridge The…
Some notes on the role of ideas in economic growth and the paper Are Ideas Getting Harder to Find? Progress studies conference slides Useful terms resource constraint - the limitations imposed on the production and consumption of goods and services due to the finite availability of resources such as labour, capital, and raw materials. endogenous growth model - a type of economic model where the…
import Image from "next/image"; I’ve been reading about and visiting California quite a lot recently. And I love it. So it feels like something worth writing about. In Britain, I think people have a reasonable sense of how the East Coast of North America came into being. But the West Coast is hazier. Prologue This blog is going to tell the story of how Europeans discovered and eventually populated…
Razib Khan on the genetic history of lactose tolerance Silver Age Marvel Comics This is a fascinating piece, even if you (like me) have no interest in Marvel. It's really a discussion written around a case study in "cultural progress". There are examples of actual innovations in things like: Stan Lee’s management style TV plot writing Ice hockey The political economy of digital government: How…
Getting stuff built Britain’s Problem with Planners The cost of the UK’s unified energy market Where next with the UK’s nuclear new build programme? The third part of the Richard Jones posts shared in the last issue. How California Turned Against Growth AI AI existential risk probabilities are too unreliable to inform policy Faith and Fate: Transformers as fuzzy pattern matchers Building A…
Getting stuff built Tornagrain is a beautiful new neighbourhood being built near Inverness. A write up of it here Hawaii has passed Senate Bill 3202 which will allow two accessory dwelling units, or ADUs, to be built on residential properties. Link Camden Council plans to pedestrianise Camden High Street The American Elevator Explains Why Housing Costs Have Skyrocketed Twenty million Londoners:…
The last links post was quite long so I think I'll try doing them weekly and including more quotes and commentary... Getting stuff built Britain There's a new government in Britain and the most important question is whether they are willing and able to fix our planning system. My friend Sam Dumitriu has the best summaries of what we know so far: Will Labour actually get Britain building again? Can…
AI How to create a web-scale dataset for training an LLM Interestingly they stopped deduplicating as aggressively as they had been. Turns out the most unique things on the web are ads and other assorted crap. Terence Tao interviewed about AI theorem provers Analysis looking at when we might hit the data wall https://x.com/lumalabsai/status/1800921380034379951 Shadow Workspace: Iterating on Code in…
Getting stuff built Gatwick Given all the debate about airport expansion, it's extraordinary that the fact the second Gatwick runway already exists isn't more widely known. This second runway was created for emergency use by upgrading the existing taxiway in 1979. However, the two runways can't be used simultaneously because they are too close to each other by a mere ten metres. When Gatwick says…
The University of Waterloo's Computer Science undergraduate degree has an extremely good reputation. I'm trying to get a sense of whether this reputation is more than anecdotal. I would also like to know if it can be explained away by e.g. selection effects, survivorship bias, simply being a very big programme, etc. If anyone has anything they think I should add or can answer any of these…
Some thoughts I wrote down in ~1 hour at the San Francisco Writing Club Upside-down teaching / Flipped classroom Eric Mazur is a professor of physics at Harvard whose students were getting perfectly adequate grades. One day though he decided to measure how much information they were retaining from his lectures. He found they largely forgot everything by the end of the lecture and even more by the…
Starting a project scrapy startproject <project_name> This creates a file structure like so: ├── scrapy.cfg └── <project_name> ├── __init__.py ├── items.py ├── middlewares.py ├── pipelines.py ├── settings.py └── spiders └── __init__.py settings.py is where project settings are contained, like activating pipelines, middlewares etc. You can change the delays, concurrency, and lots more things.…
The diagram below illustrates how we can approximate the area under the curve $y = ln(x)$. By dividing the curve up into segments we can have created a set of trapezia. The area of each trapezium is the average of the heights of its two parallel sides multiplied by its width: $$ \text{area} = \frac{y(x_1) + y(x_2)}{2}\cdot \Delta x $$ The total area under the curve is going to be the sum of the…
The Art of Doing Science and Engineering features some mathematics that I found a little difficult to follow. These are some notes I've made to help fill in the gaps. Chapter 1 Hamming makes two claims: Scientific knowledge doubles every 17 years 90% of scientists who have ever lived are now alive He makes these claims in order to give an example of back-of-the-envelope calculations that you can…
2.1 (a) Is row 1, column 2 a Nash equilibrium? (In all the strategic form games in these problems, the payoff of the person selecting the row is given first.) $$ \begin{array}{c|c|c} & \text{column 1} & \text{column 2} \ \hline \text{row 1} & 0,0 & 6,6 \ \hline \text{row 2} & 2,2 & 7,0 \end{array} $$ No. In game theory, a Nash equilibrium for a two-player game in normal form is a pair of…
The chain rule is a fundamental concept in calculus that allows you to compute the derivative of a composite function. In other words, if you have a function that is formed by combining two or more functions, the chain rule helps you find the derivative of the resulting function with respect to its input variable(s). Mathematically, the chain rule states that for two functions, $f(x)$ and $g(x)$,…
Your heating bill depends on the average temperature outside. If all other factors remain constant, then the heating bill will increase when the temperature drops. Let's denote the average temperature by $t$ and define a function $h:\mathbb{R}\to\mathbb{R}$ where $h(t)$ is the heating bill as a function of $t$. We can then interpret the ordinary derivative as indicating how much the heating bill…
The product rule is a fundamental concept in calculus used to compute the derivative of the product of two functions. If you have two functions, $f(x)$ and $g(x)$, the product rule helps you find the derivative of their product $$ h(x) = f(x)g(x) $$ with respect to $x$. Mathematically, the product rule states that: $$ h'(x) = f'(x)g(x) + f(x)g'(x) $$ where $h'(x)$ is the derivative of $h(x)$ with…
The quotient rule is an important concept in calculus used to compute the derivative of the quotient (division) of two functions. If you have two functions, $f(x)$ and $g(x)$, the quotient rule helps you find the derivative of their quotient $$ h(x) = \frac{f(x)}{g(x} $$ with respect to $x$. Mathematically, the quotient rule states that: $$ h'(x) = \frac{f'(x)g(x) - f(x)g'(x)}{f(x)^2} $$ where…
The general form of a second degree equation is $$ x^2 + px + q = 0 \tag{0} $$ where $p$ and $q$ can be any real number and $x$ is the roots of the equation. In equations of this form $q$ is the product of the roots and $p$ is the sum of the roots. Equations of the form $x^2 + q = 0$ are easy to solve because $p = 0$. The roots are simply $±\sqrt{x} - q$. The graphical representation of equations…
2026 The Dream Endures: California Enters the 1940s - Kevin Starr Lone Star: A History of Texas and the Texans - T. R. Fehrenbach The Brothers Karamazov - Fyodor Dostoyevsky The Kellys and the O'Kellys - Anthony Trollope Georgiana, Duchess of Devonshire - Amanda Foreman Screwtape Proposes a Toast - C.S. Lewis The Screwtape Letters: Letters from a Senior to a Junior Devil - C.S. Lewis The Barbary…
Command Line for Unix and Windows Action Unix Windows Notes Print working directory pwd pwd Change directory cd cd Make directory mkdir List contents ls dir -a to include hidden files Remove directory rmdir Only works if directory is empty Remove directory and contents rm -rf Create file touch Remove file rm Git Action Command Notes List local branches git branch Prune local branches git fetch -p…
This document is somewhat inspired by Stephen Diehl's What I Wish I Knew When Learning Haskell and Evan Chen's An Infinitely Large Napkin . What is a gene? Mendelian Genetics Bio The central dogma of biology (coined by Francis Crick) says that information flows in one direction from DNA to RNA to proteins . Pieces of DNA called exons are transcribed into RNA. RNA is molecularly the same as DNA,…
A list of blogs, newsletters, podcasts, and publications that I like General Interest Astral Codex Ten / Slate Star Codex The best blog and former blog on the internet. Scott Alexander would be my guess for the contemporary writer most likely to be cited in the next century. Marginal Revolution Tyler Cowen is an "infovore". He coined the term I think. He and Alex Tabarrok push new content every…
There are some things you read that strongly affect the way you look at the world. I've started to gather a list of such things here. These are approximate categories. Most things could be placed in many. General Thoughts on Meaning and Writing - Matt Lakeman Politics I can tolerate anything except the out-group - Scott Alexander This is the first Scott Alexander blog post that I read and the…
Near the end of the 7th century, Bishop Wulfram attempted to convert the pagan king Rathbod of Frisia. Despite his remonstrances, the King would not do away with his people’s ancient custom of human sacrifice. It is said that Wolfram saved a man named Oven from hanging. For two hours Wulfram prayed on his knees while the youth hung by his neck. Then when he stood the rope snapped and Oven was…
In documentaries on the history of mathematics, there is often a scene where the presenter discusses the invention of the number zero. If there is enough money they might even get to fly out to India to do it. It always seemed strange to me that "zero" was a concept that needed discovering. Surely if you asked someone in Rome what happens if you take 3 denari from a person with 3 denari, they…