Alex Molas Blog
https://alexmolas.com (RSS)
I’ve never been good at playing football 1. I started playing again last year and I have scored more own goals than goals for my team. Also, I support the RCD Espanyol 2, which has spent last season in the second division and has miraculously ascended to the first division last week. And to be honest, I only watch games to spend time with my...
For the last weeks at Wallapop, we have been interviewing candidates for a Data Scientist position. Our current interview process is quite standard, but there are some things we would like to change about the process. We were talking about it during lunch, and I saw my opportunity to propose one of my hot takes: “We should start doing Leetcode...
The other day I was interviewing a developer for a position at Wallapop. The candidate was a little bit junior, but I enjoyed their technical assignment and the conversation was going great. One of the questions I had to ask was
Explore the critical considerations and potential pitfalls of relying solely on A/B testing in making business decisions. While A/B testing is a valuable tool, this post challenges the assumption of exchangeability between past and future data, emphasizing the dynamic nature of the business environment. I propose two solutions (1) validating the...
In this post I explain how I built a search engine from scratch using python. The resulting search engine is used to search in the posts of the blogs I follow.
Here I explore a doubt I've had for the last 15 years. I vaguely remember a phrase attributed to Voltaire or Robespierre. The phrase was " I'm not a believer, but I prefer my barber to be a Christian, even more, when he's using his razor on my neck". For the last 15 years, Google has failed me to find who was the author of this phrase. But today...
Insights and tips for a smooth transition when starting a new job
I hate MFA, and in this rant post I explain why. It's basically because (1) is distracts me a lot, (2) it forces me to have a smartphone, (3) it's a leaky abstraction, and (4) it can be replaced with better solutions.
This insightful exploration draws parallels between mathematical formulations and practical implementations, showcasing how understanding conditioning as grouping can elevate your statistical insights. Discover the parallels between conditional expectations like $\mathbb{E}(y | X=x)$ and popular grouping techniques found in data analysis tools...
November 14, 2023 · 7 mins · 1297 words tldr Escape from Alcatraz is the least controversial movie ever, and The Room is the most controversial. Background I tend to discuss a lot with my friends, even more so after a beer or two. I believe our friendship is built upon countless hours discussing almost every topic you can imagine. One of the topics we usually discuss is movies and...
Discover the surprising wisdom in embracing 'dumbness.' Learn from a remarkable grandmother-in-law who mastered the art of asking for help by appearing clueless. Explore the benefits of reducing cognitive load, saving time, and focusing on your priorities. Uncover when to apply this strategy and when it's best to rely on your expertise.
Understand the different types of means and when to use them.
In this post I derive the physics of pumping a swing and the physics of jumping from a swing. Then, using both pieces I compute the optimal strategy of jumping from a swing to maximize the traveled distance. I propose this game as a new Olympic sport.
In this short note I compare Bilalic and Blom approximations to compute the k-th order statistics from a gaussian distribution.
Does it exist a gender gap in chess? Why is it that the best players are men? Is there any fundamental difference between how men and women play this game?
In this text, I study the idea that science needs engineering as much as engineering needs science. I defend the position that doing good science without following best engineering practices is impossible.
In this text I use math to show that you have a rare skill combination, that makes you the best at something.
In this post I explain how I built my automatic blogroll using Github Action and Github Pages.
Quick blog update. Since last Tuesday (2023-07-18) I’m a proud member of the 512KB club. I am aware it doesn’t sound very ambitious, but it serves as a small reward after having completely refactored my blog.
July 18, 2023 · 5 mins · 1069 words This is an old note I took to myself a few months ago when I was learning about computability theory. It was just a couple of bullet points, so I rewrote them in a better format and added some images. Hope you enjoy it. During these last weeks I’ve been reading about computability theory. Of all the amazing things I learned, the ones that surprised me more are the ones related with...
Nobody cares about your blog, but you should keep writing!
Discover the reasons behind the transformation of my blog and the benefits it brings. Experience faster writing, simplified design, reduced distractions, and a sense of complete ownership. Explore the enhanced aesthetics that prioritize minimalist style and direct communication. Find out why this revamped blog reflects my unique vision.
Since last October, I’ve been playing in a simple game all by myself, with just one rule - I have to spot all the license plates from 0000 to 9999 in sequential order. Where I live, license plates follow this format: XXXX - AAA, where XXXX represents 4 numbers, and AAA are three letters.
In our modern era, we have witnessed a remarkable shift in the way we approach computation. We no longer rely solely on physical machines housed within our premises; instead, we rent computers in the ethereal realm of the cloud. It’s a convenient arrangement that grants us access to computational power without the hassle of maintenance or...
Investing your money wisely is crucial for financial success. In this post, I delve into the popular strategy of dollar cost averaging (DCA) and compare it to the lump sum (LS) approach. By analyzing S&P 500 data from the past 40 years, I show that DCA is generally suboptimal, with LS outperforming it in 82% of cases, resulting in a 23% higher...
Are you sick of having to choose which political party to vote for when none of them represents your beliefs 100%? In this post, I am going to explain a practice that will end your headaches when voting.
Learn how initializing the correct bias in your neural network can speed up training process through analytical derivation and experiments.
The uncertainty of a measure is a statistical process. The standard approach to measure a quantity is to repeat the measure a number of times, compute the mean and its standard error. It is based on the assumption that measuring is an imperfect process, and therefore when measuring some quantity, an error is introduced. This post goes down the...
In this post, I show how can we leverage the extra information we get from knowing that a car has survived a certain amount of time. I formalize the idea mathematically and then build a framework to optimize the total costs.
In this post I analyze all the available Chess960 games played in Lichess. With this information I show that there are no starting positions that favor any of the players more than other positions.
Today I’m going to write about the most typical topic of the last days of the year: New Year’s resolutions. The usual schema for this post is to review one last year’s resolutions and write down the resolution for the starting year. However, I didn’t write any list for this ending year, so I’ll just do a quick summary of the year and write down...
In this short post I show a position where's possible to mate using only pawns. Also, the mate is optimal, in the sense that the game can't we won using less movements.
During my current incursion in computability theory I learnt about uncomputable numbers, this is, numbers that can’t be computed with arbitrary precision. This means that even given all the computational power in the universe you could not compute these numbers. Even if God himself came from Heaven, he could not compute these numbers....
During these last few days I’ve been reading a little bit about computability theory, and I feel like a kid with a new toy, so I’m going to write some posts about this topic. I don’t pretend to explain anything new, and probably what I’m going to write has been written before, but I’ll write these posts for two reasons: (1) as future notes for...
A game where you have to choose the smallest number that nobody has chosen yet.
How does python optimize constant expressions.
How to interpret L1 regularization using a Bayesian approach.
A review of my first -and for the moment the only- paper published in a top journal.
Treating your laptop as an implementation detail can help your productivity.
How to use boolean algebra to vectorize complex operations and get x2000 speed-up.
List of checks to pass before starting a new data science project.
Developing a better understanding and intuition about what really means to minimize the mean squared error.
How to create a warmup file for your tensorflow model using TFRecordWriter and tensorflow_serving.apis.
Why the combination of bureaucracy and computerization is breaking our society.
Introduction and solution of the Feynman's Restaurant Problem.
A counterintuitive experiment with fair coins.
Speeding up TensorFlow training.
How to train a tensorflow model when your training dataset doesn't fit in memory?
Deriving same equations with different methods
What is and how to play continuous blackjack?
I still remember when I started working as an intern data scientist and I had to open my first pull request. I was very happy with my work, so I just committed all my changes together, opened a pull request, assigned it to my supervisor, and started waiting for the compliments to arrive - spoiler: the compliments never arrived.
Learning how to multiply matrices in the best possible order, ie solving the Matrix Chaing Multiplication problem.