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Brandon Rohrer
@brandonrohrer.com
3.6K followers 2.3K following 660 posts
Robotics and Reinforcement Learning tinkerer.
brandonrohrer.com
Wrangler of algorithms for Confluence @ Atlassian.
Eater of bread. Sipper of whisky.
Reports to a Shih Tzu.
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Brandon Rohrer @brandonrohrer.com · May 28
Update from my long-running #ReinforcementLearning side project.

It uses a combination of new tools to control a simulated pendulum.
Solving an easy RL problem on hard mode Brandon Rohrer A story about a reinforcement learning approach learning to make a pendulum stand up straight, while making very few assumptions. tl;dr This is a demonstration of an RL approach that uses a combination of new tools to control a simulated pendulum: BucketTree to learn a discretization of the pendulum’s continuous state variables, angle and angular velocity, Ziptie to bundle the discretized values into discrete states, Fuzzy Naive Cartographer (FNC) to learn common state-action-state sequences and to make conditional predictions of reward for each action. It all runs in Myrtle, a real-time reinforcement learning workbench. This approach requires only a little domain specific design and makes very few assumptions about its world. The physical representation of the pendulum is simplistic. The arm has uniform mass. It has a small amount of rotational friction, proportional to its speed. And gravity acts on the pendulum's center of mass, pulling it downward. As always, the canonical source of information is the code itself. Sensors There are two quantities returned by sensors: pendulum position and rotational speed. Position, θ, is measured in radians, zero when pointing straight down, θ = π/2 when pointing to the right, θ = π when pointing upward, and continuing around to almost 2π when it reaches the bottom again and resets to 0. Angular speed, ω, is measured in radians per second. Positive angular speed is counter-clockwise (the direction of increasing position) and negative speed is clockwise. Actions Actions take the form of torque, τ, applied to the base of the pendulum. Positive torque accelerates the pendulum counter-clockwise, in the direction of increasing position. Negative torque accelerates it in the clockwise direction. Actions are discrete in time. Each action is a constant torque that lasts for 1/8 second. There are 13 discrete values the torque can take, 6 positive, 6 negative, and zero. Possible torque values are distributed nonuniformly across the range, with the middle half of the range having denser coverage. This results in a finer grained representation of small torques, useful for making fine-tuning adjustments. Reward The pendulum returns reward, r, related to how high the its swinging end reaches, its vertical distance from its straight down θ = 0 position. It reaches a maximum of r = 2 at the straight up θ = π position. A successful learning curve will work its way up to 2 and stay there.
Reposted by Brandon Rohrer
joanwestenberg.com
I've been writing a weekly essay for a while now. Tech, culture, the stuff that keeps me up at night.

People seem to like it.

It's free to subscribe:

www.joanwestenberg.com
Westenberg.
Where Builders Come to Think.
www.joanwestenberg.com
November 18, 2025 at 9:11 AM
brandonrohrer.com
* googling six seven *
How do you do, fellow kids?
November 15, 2025 at 2:36 PM
brandonrohrer.com
New Post: Autoblocking bots and scrapers in your server
brandonrohrer.com/hosting6.html

This one also comes with code:
codeberg.org/brohrer/webs...
In my last post I said "Automating firewall updates will be an adventure for another day." Today is that day. This is the latest in a growing series on hosting your own static blog. ( I, II, III, IV, V VI VII ) Protecting your website requires you to keep your eyes on it at all times. That can get tiring. Sometimes you need to eat and sleep and maybe work for a living. It can be useful to have automated helpers to fill those gaps. Detection The first step in keeping your blog traffic healthy is to be able to detect when someone is doing something they shouldn't. In my traffic control post I described five behaviors that I wanted to limit Scanning for secrets Fishing for files Rapid-fire requests Trying to hide rapid-fire requests Attempting unsupported actions The post describes these in words, but they need to be made more specific before they can be enforced by an automated detector. Doing this step well is where most of the art and cleverness is required. If you define a rule too narrowly, there will be a lot of IP addresses that should get blocked, but get missed (false negatives for the detector). On the other hand, if you define a rule too broadly, there will be a lot of legitimate IP traffic that gets blocked (false positives) and you will have a lot of sad readers who can't access your cat pictures.
November 12, 2025 at 12:37 PM
brandonrohrer.com
the gift for the one who has everything
Etsy webpage $69.00 Lobotomy Orbitoclast , Knife & Hammer Surgical Medical Tools This is the Museum quality replica version you will not find anywhere else You will receive 1 orbitoclast pick , 1 lobotomy knife, and 1 hammer
November 11, 2025 at 2:52 PM
Reposted by Brandon Rohrer
shappy.bsky.social
Little known fact. This is how @johnathan.bsky.social and I write our newsletter every two weeks.
November 8, 2025 at 2:58 PM
brandonrohrer.com
#NaNoWriMo tip for breaking writers block - write the most profane version you possibly can. F-bombs every other word. Make it filthy. If you run out of content, just string together swears.
November 8, 2025 at 1:46 PM
brandonrohrer.com
The Offal Office
aguywhocodes.com Michael Brown 🍉 @aguywhocodes.com · 13d
You can pay for school but you can't buy class
onestpress.onestnetwork.com Olga Nesterova @onestpress.onestnetwork.com · 13d
New sign outside the Oval Office..
November 5, 2025 at 5:19 PM
Reposted by Brandon Rohrer
pfrazee.com
One of the huge perks of working at a software company is, when there's something about the product that bothers you personally, you can get your hands dirty and find out why it's basically impossible to get fixed
November 4, 2025 at 11:00 PM
brandonrohrer.com
When @mittechreviewbr.bsky.social is calling out the emperor’s lack of clothing, the game is almost over

www.technologyreview.com/2025/10/30/1...
How AGI became the most consequential conspiracy theory of our time
The idea that machines will be as smart as—or smarter than—humans has hijacked an entire industry. But look closely and you’ll see it’s a myth that persists for many of the same reasons conspiracies d...
www.technologyreview.com
November 3, 2025 at 8:43 PM
Reposted by Brandon Rohrer
sarasoueidan.com
Those of you who've followed me long enough may know that I don't keep my birds in cages. And at some point I start to let them out. They may choose not to come back, but that's a risk I am willing to take if they're ready to live "on their own".

This one came back today.
November 2, 2025 at 12:06 PM
Reposted by Brandon Rohrer
victorsvector.com
that's why i made this script to automatically let me know when things break. but of course that could fail too, so there's another system that notifies me if *that* breaks. but of course that could fail, so...
November 1, 2025 at 2:13 PM
brandonrohrer.com
Automation doesn’t guarantee that the thing won’t break. Automation only guarantees that when the thing does break you won’t be watching.
November 1, 2025 at 1:39 PM
Reposted by Brandon Rohrer
jmsdnns.bsky.social
a like on a skeet about a green checkmark must be INTENSE
October 30, 2025 at 4:28 PM
brandonrohrer.com
I thought a social media like was a good dopamine hit but goddamn a green checkmark on a pipeline build step is the real shit
October 30, 2025 at 4:22 PM
Reposted by Brandon Rohrer
norootcause.surfingcomplexity.com
On the one hand, I often feel like I'm just writing the same blog post over and over again. On the other hand, I feel like the resilience engineering concepts I'm writing about still have yet to be widely disseminated in our industry.
October 26, 2025 at 3:59 AM
brandonrohrer.com
A deeply insightful post in which Lorin reprises his role as Cassandra. The curse of the systems thinker.
October 26, 2025 at 12:33 PM
Reposted by Brandon Rohrer
eva.computer
white house has joined bluesky
click here to block all official us government accounts instantly

bsky.app/profile/did:...
October 17, 2025 at 10:08 PM
brandonrohrer.com
#stats poll
a. Bonferroni
b. Holm
c. Hommel
d. Benjamini-Hochberg
e. YOLO
October 16, 2025 at 6:52 PM
brandonrohrer.com
A friend of a friend made this and the aesthetics are deliciously DIY. If you like it, please "LIKE" it and help them win a SfN competition.

youtu.be/RCjua7f2v9U?...
Something to Savor: The Neuroscience of Flavor
YouTube video by BrainFacts.org
youtu.be
October 15, 2025 at 12:37 AM
brandonrohrer.com
If you had told me six months ago that the tv episodes I would be sitting around waiting for each week was Peacemaker I wouldn’t have believed you 
October 11, 2025 at 12:56 AM
brandonrohrer.com
In our house, we have a 10 ounce jar of Herrell’s hot fudge that is about to go out of date. Tensions are high. I have, heroically, picked up a spoon.
October 9, 2025 at 2:35 PM
brandonrohrer.com
New post: Controlling IP traffic on your webserver

A cool part about having your own webserver is that you get to choose who can visit. When IP addresses try to access sensitive files or aggressively scrape, you can just block them.

Here's how.

brandonrohrer.com/hosting5.html
Block an IP address The most straightforward way to block and IP address is in the firewall. It is the tool build specifically for this. To block the address 101.101.101.101, run from the command line sudo ufw insert 1 deny from 101.101.101.101 This instructs ufw (the Uncomplicated FireWall) to insert a rule at the the top of the list (position 1) to deny all incoming traffic from the address. After running this, no restart of the firewall is needed. The rule is active. (ufw docs The position 1 is important because in ufw, the first rule that matches is applied. If there was a rule to allow all addresses that started with 101. and that rule came before the deny rule, then the deny rule would never be reached. While it's possible to block specific ports, or even to block an IP address from seeing particular pages, complex rules and conditions get difficult to analyze very quickly, and can lead to cases where there are loopholes. Use fancy rule combinations sparingly. Parse logs In their raw form access logs are technically human-readable, but they are a lot. I found it really useful to do a little parsing to pull out the bits I'm interested in. (I'm working with the default nginx log format, so adjust this according to your own.) I wrote a script to take advantage of the repeatable structure of these logs to dissect them into their parts. It uses tricks like splitting the log based on brackets and spaces. It productes a pandas dataframe with columns containing the IP address, requested URI, HTTP status code, and every component of the date and time.
October 9, 2025 at 12:19 AM
Reposted by Brandon Rohrer
brandonrohrer.com
Setting: Classic Tintin and Captain Haddock meme, modified Wednesday Addams: What a week, huh Sergeant? Captain: Wednesday, it's Captain
October 1, 2025 at 1:30 AM
brandonrohrer.com
Setting: Classic Tintin and Captain Haddock meme, modified Wednesday Addams: What a week, huh Sergeant? Captain: Wednesday, it's Captain
October 1, 2025 at 1:30 AM
brandonrohrer.com
They don’t tell you an engineering school how much of your job will be telling the future.
September 29, 2025 at 11:53 AM