Large Language Models for Cycling

Amid the fanfare about the extraordinary AI capabilities of large language models (LLMs), the race is on to produce LLM applications that actually do something useful. Several hurdles obstruct the way forward, including confabulation, privacy and limitations of training data. This article explains how Retrieval-Augmented Generation can address some of these issues and help find out some useful information about cycling.

Confabulation

Since they are trained only to predict the next word in a sentence, LLMs have no understanding of the text they generate. They can have a tendency to intersperse facts with inaccurate or untrue statements in a manner that seems entirely plausible and convincing. You should not rely on an LLM for advice on important decisions without validating its response. Note that if you ask an LLM for its sources, the citations may be imaginary or if they exist the references may not support the assertions.

One way to reduce the risk of confabulation is to ask the LLM to base its answer selected relevant documents.

Privacy

If you use an online ChatBot, everything you type or upload is stored on the provider’s server. This can be used as further training data or for snooping on users. There is a significant risk that a lot of personal and proprietary company information has already been hoovered up in this way. Companies need ways to sandbox internally developed LLM tools that contain sensitive data and prevent leakage of confidential information.

Privacy can be addressed by running LLMs on local networks. This is possible because inference is a simple task relative to training, which requires banks of data servers. Many free open-source models are available. Running an open-source model locally also avoids paying a subscription to an online provider.

Limitations of training data

LLMs are trained on vast generic data sets. This is a very expensive task, so they are typically frozen at some point in time. If you ask an LLM about current news events, it will typically tell you that it was trained on data up to a certain date in the past and has no knowledge of the event. The models may also lack specialised data in narrow domains.

RAG provides a way to supplement the original training set with selected additional information relevant to the field of interest.

RAG

Retrieval-Augmented Generation is an approach that provides an LLM with additional information to help it answer a query. For example, when asked about current affairs, it would be very helpful to retrieve a copy of today’s newspaper. Companies may wish to develop LLM-based applications with specialist knowledge of internal documentation. RAG makes this possible.

When you interact with an LLM, your conversation is presented to the model in the form of a huge string of numbers called an embedding. LLMs are trained so that sentences with similar words and meanings have similar embeddings. The idea of RAG is to take one or more relevant supplementary documents, split them up into chunks and store the embeddings of these chunks in a vector database. When a user presents a query, the database retrieves the embeddings of chunks that most closely match the query. In this way, the query can be augmented with relevant chunks of text from the source material. Note that this avoids the need to do additional expensive training or fine-tuning of the LLM on specialist topics.

One weakness of RAG is that most LLMs have not been trained specifically on the types of prompts used in RAG, though some companies, like Cohere, are working on this.

Cycling Through the Pandemic

I decided to try this out using a freely available book called Cycling Through the Pandemic, which has the slightly cryptic subtitle, Tactical Urbanism and the Implementation of Pop-Up Bike Lanes in the Time of COVID-19. This 250-page book was published in 2024, so it could not have been part of the training set for the LLM that I was using.

It is unbelievably easy to download and then run an open-source LLM on your local machine. All you need to do is download LM Studio. I decided to use an open-source LLM model called Meta-Llama-3.1-8B-Instruct-GGUF. I dragged and dropped the pdf of the book into the chat-box and started asking questions.

A transcript of my conversation is recorded below. At each step, LM Studio retrieved three chunks of text from the book it considered most relevant to the query, allowing me to check the reliability of the model’s interpretation.

The model answered in good English, basing its responses on the content of the book. It corrected itself when challenged on the claim that Bogotá is in France. It even responded in French to a question posed in French. In my view, RAG can be used to produce genuinely useful applications for LLMs.

RAG dialogue based on a book about the impact of COVID 19 on cycling

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CyclingCOVID.pdf

What is tactical urbanism

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Based on the provided information, tactical urbanism refers to a type of urban planning that involves temporary and low-cost interventions aimed at introducing rapid changes to urban spaces with a broader purpose in mind (Lydon and Garcia 2015). It can be seen as a practical approach to urban change where many small actions implemented at the hyper-local level can achieve longer-term goals of creating a liveable, walkable, sustainable community.

Tactical urbanism often involves shortcuts or rapid and unbureaucratic actions taken by municipalities in response to crises (Citation 1). It can be associated with grassroots initiatives but can also be used by authorities. This approach has been implemented in various contexts, including during the COVID-19 pandemic.

Tactical urbanism is characterized by its focus on temporary and flexible material approaches to urban change, which can be both a practical tool for citizens and enterprising governments alike (Citation 3).

It’s worth noting that there are different perspectives on tactical urbanism, with some viewing it as a means of achieving substantive change without state action, while others see the increasing professionalization of these activities as borrowing their material design language (Citation 2).

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Why was cycling boosted by COVID 19?

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Cycling saw a boost during the COVID-19 pandemic for several reasons (Citation 2). Firstly, people had less need to travel due to home working and distance learning. Secondly, the fear of infection led to a strong decline in ridership on public transport, which benefited cycling. Additionally, active mobilities such as cycling were promoted as a means of staying fit and getting exercise when other recreational facilities were closed.

The pandemic also led to an increase in cycling for leisure activities (Buehler and Pucher 2021b), with the strongest increase seen on weekends and in the afternoon. This shift towards cycling as a leisure activity is likely due to the rise of “undirected travel,” or trips without a specific destination, which was encouraged by social distancing measures.

In France, for instance, the first COVID-19 related lockdown led to a rapid increase in cycling use (Buehler and Pucher 2022) and implemented temporary cycle paths. Governments saw cycling as a solution to develop health-friendly mobility while responding to the possible desertion of public transport due to fear of catching the virus (Citation 3).

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Has the COVID related boost in cycling persisted

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The survey conducted in Geneva and Lausanne (Rérat et al. 2022; Schmassman and Rérat 2022) found that the COVID-related boost in cycling has largely persisted. The majority of respondents reported cycling as much or more often than before the pandemic, with a significant number even starting to cycle for the first time.

In Geneva, 42% of respondents cycled as much as before, while 44% cycled more often. In Lausanne, 58% cycled as much as before, and 27% cycled more often. This suggests that many people have adopted cycling as a mode of transport during the pandemic and are likely to continue using it.

The fact that 81% of respondents in Geneva (73% in Lausanne) agree or strongly agree that COVID cycle lanes make them feel safer also suggests that these temporary infrastructure projects had a lasting impact on cyclist safety and behavior.

However, as mentioned by Citation 2, the long-term sustainability of this boost is still uncertain. The study notes that most cycling infrastructure implemented during the pandemic involved existing projects, and it remains to be seen whether this “leap forward” will make a lasting difference in the trajectory of local public action or simply represent a spike on an upward graph.

Overall, while there are indications that the COVID-related boost in cycling has largely persisted, further analysis is needed to determine its long-term impact.

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What has been the impact specifically in London?

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The impact of temporary cycling infrastructure and “Tactical Urbanist” approaches in London is a complex issue with both positive and negative effects.

Positive impacts include:

The introduction of School Streets, which have shown to promote mode shift towards active modes of travel (Hopkinson et al. 2021) and improve air quality at schools (Air Quality Consultants 2021).
The implementation of temporary cycle lanes and other small-scale projects aimed at improving the smaller residential or local streets in London.
These efforts are part of the Healthy Streets approach, which aims to promote a more sustainable transportation system in London.
However, there have also been negative impacts, including:

Variable outcomes between sites, with some schemes showing little effect (Citation 2).
Criticisms that some projects were implemented too quickly or without adequate consultation, leading to concerns about the speed and process of decision-making.
Vandalism of planters, bollards, and cameras used to prevent through-traffic in some areas (Citation 3).
Removal of Low Traffic Neighbourhoods, especially in Outer London, due to opposition from local residents.
The Temporary City report by Asa Thomas highlights the importance of balancing big change with small impact, emphasizing the need for careful planning and consultation when implementing new transportation projects.

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What research was done in French cities?

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The research on French cities during the COVID-19 pandemic focused on understanding how urban planners and policymakers implemented measures to promote cycling and improve public transportation.

A study examined five French cities: Grenoble, Lyon, Montpellier, Rennes, and Bogotá (Citation 1). The study found that these cities had varying levels of population size, density, and surface area. For example, Bogotá was the most populous city with over 7 million inhabitants, while Grenoble had a smaller population of around 160,000.

Another study looked at the implementation of measures in French cities during the pandemic (Citation 2). The research found that some cities focused on improving cycling infrastructure within the city center, such as Lyon and Rennes. In contrast, other cities prioritized links between periurban municipalities or outer suburbs.

A book titled “Changing Bikeability: Everyday Cycling in Developed Territories” explores changing bikeability in French cities during the pandemic (Citation 3). The book examines six French cities: Grenoble, Lyon, Montpellier, Paris, Rennes, and Saint-Étienne. The research found that each city had its unique characteristics and ways of implementing measures to promote cycling.

These studies provide insights into how different types of cities implemented measures to improve cycling infrastructure during the pandemic, and whether these measures were made permanent.

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Is Bogotá in France?

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No, Bogotá is not in France. According to Citation 1 and Citation 2, Bogotá is located in Colombia, and it has been compared with four French cities: Grenoble, Lyon, Montpellier, and Rennes.

In fact, the study mentioned in Citation 3 compares the cycling infrastructure in these four French cities (Grenoble, Lyon, Montpellier, and Rennes) with that of Bogotá, a city located in Colombia.

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Quels ont été les résultats à Grenoble ?

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Les résultats obtenus à Grenoble sont mentionnés dans la citation :

“Nous avons contacté le Syndicat Mixte des Mobilités de l’Aire Grenobloise et réussi à obtenir la base de données du réseau cyclable. De plus, un stagiaire a effectué une interview avec un technicien de cette organisation, et sur plusieurs occasions, il est allé visiter le site pour voir si les voies temporaires (pop-up tracks) existaient toujours.”

Cela indique que les auteurs ont réussi à collecter des données sur le réseau cyclable de Grenoble en contactant la Syndicat Mixte des Mobilités de l’Aire Grenobloise et en effectuant une interview avec un technicien. Cependant, il n’y a pas d’information sur les résultats concrets de ces efforts.

Cependant, on peut trouver plus d’informations dans le graphique (Figure 8.2) qui montre différents types de voies temporaires installés dans les cinq villes étudiées, dont Grenoble.

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Cyclo-Social Networks

When Mexico’s Isaac del Toro and the Brit, Finlay Pickering, joined World Tour teams in 2024, they became part of an elite group. The structure of the professional cycling community differs from other types of social network, because the sport is organised around close-knit teams. You may have heard of the idea that everyone in the world is connected by six degrees of separation. Many social networks include key individuals who act as hubs linking disparate groups. How closely connected are professional cyclist? Which cyclists are the most connected?

Forming a link

An obvious way for cyclists to become acquainted is by being part of the same team. They spend long periods travelling, training, eating and relaxing together, often sharing rooms. Working as a team through the trials and tribulations of elite competition develops high degrees of camaraderie.

Each rider’s page on ProCyclingStats includes a team history. So I checked the past affiliations of all the current UCI world team riders. The idea was to build a graph where each node represented a rider, with edges connecting riders who had been in the same team. Each edge was weighted by the number of years a pair of riders had been in the same team, reflecting the strength of their relationship.

Cyclo-social network

The resulting graphical network, displayed at the top of this blog, has some interesting properties that reveal the dynamics of professional cycling. The 18 world tour teams are displayed in different colours. The size of each rider node is scaled by length of career. An experienced rider, like Geraint Thomas, has a larger node and more connections, which are shown as light grey lines, where the thickness represents years in the pair of riders were in the same team. Newer riders, with fewer connections tend to be on the periphery. For example, Isaac del Toro is the orange UAE Team Emirates rider at the top.

There are no fixed rules about how to represent the network, but the idea is that more closely related riders ought to congregate together. The network shows INEOS near UAE as shades of orange in the top right. Next we have Team Visma Lease a Bike in cyan, around two o’clock, close to Lidl – Trek in light green, Bahrain – Victorious in darker blue and Cofidis in lighter blue. Yellow Groupama – FDJ lies above the dark brown Jayco AlUla riders in the lower right. Red Movistar, light green Team dsm-firmenich PostNLand light blue BORA – Hansgrohe are near 6 o’clock, though Primož Roglič lies much closer to his old team. Decathlon AG2R La Mondiale is light blue in the lower left, near the darker blue of Alpecin – Deceuninck and pale green EF Education – EasyPost. Astana is orange, around nine o’clock. Dark blue Soudal Quick-Step, lighter blue Intermarché – Wanty and red Arkéa – B&B Hotels all hover around the top left. Teams that are more dispersed would be indicative of higher annual turnover.

3 degrees of separation

No rider is more than three steps from any other. In fact the average distance between riders is two steps, because the chances are that two riders have ridden with someone in common over their careers. Although the neo-pros are obviously more distantly connected, Isaac del Toro rides with Adam Yates, who spent six years alongside Jack Haig at Michelton Scott, but who now rides for Bahrain Victorious as a teammate of Finlay Pickering.

Bob Jungels is the most connected rider, having been a teammate of 100 riders in the current peloton. Since 2012, he has ridden for five different teams. He and Florian Senechal are only two steps from all riders. The Polish rider Łukasz Wiśniowski has been with six teams and has 94 links. Then we have Mark Cavendish with 91 and Rui Costa with 89.

In contrast, taking account of spending multiple years as teammates, Geraint Thomas tops the list with 218 teammate years. Interestingly, he is followed by Jonathan Castroviejo, Salvatore Puccio, Michal Kwiatkowski, Luke Rowe, Ben Swift, all long-time colleagues at INEOS Grenadiers. This suggests they are very happy (or well paid) staying where they are.

If we estimate “long-term team loyalty” by number of teammate years divided by number teammates, Geraint is top, followed by Salvatore Puccio, Michael Hepburn, Luke Durbridge, Luke Rowe, Simon Yates and Jasper Stuyven.

Best buddies

The riders who have been teammates for the longest are Luke Durbridge/ Michael Hepburn and Robert Gesink/Steven Kruijswijk both 15 years,
Geraint Thomas has ridden with Ben Swift and Salvatore Puccio for 14 years and Luke Rowe with Salvatore Puccio for 13.

Outliers

In a broader analysis that includes all the Pro Continental teams alongside the World Tour, the graph below shows a notable team of outliers. This is Team Novo Nordisk for athletes who compete with type 1 diabetes. Their Hungarian rider, Peter Kusztor, was the teammate of several current riders, such as Jan Tratnik, prior to joining Novo Nordisk, in a career that stretches back to 2006. The team is an inspiration to everyone affected by diabetes.

Analysis

This analysis was performed in Python, using the NetworkX library.

Code can be found here.

How many heartbeats?

The fascinating work of Geoffrey West explores the idea of universal scaling laws. He describes how the lifetimes of organisms tend to increase with size: elephants live longer than mice. On the other hand, average heart rate tends to decrease with size. It turns out that these two factors balance each other in such as way that over their lifetimes, elephants have roughly the same number of heartbeats as mice and all other animals: about 1.5 billion.

Less active people might be tempted to suggest that indulging in exercise reduces our lifetimes, because we use up our allocation of heartbeats more quickly. However, exercisers tend to have a lower resting heart rate than their sedentary peers. So if we really had a fixed allocation of heartbeats, would we be better off exercising or not?

Power laws

To get a sense of how things change with scale, consider doubling the size of an object. Its surface area goes up 4 times (2 to the power of 2), while its volume and its mass rise 8 times (2 to the power of 3). Since an animal loses heat through its skin whereas its ability to generate heat depends on its muscle mass, larger animals are better able to survive a cold winter. This fact led some scientists to suspect that metabolism should be related to mass raised to the power of 2/3. However, empirical work by Max Klieber in the 1930s found a power exponent of 3/4 across a wide range of body sizes.

Geoffrey West went on to explain the common occurrence of the 1/4 factor in many power laws associating physiological characteristics with the size of biological systems. His work suggests that this is because, as they evolved, organisms have been subject to the constraints of living in a 3-dimensional world. The factor, 4, drops out of the analysis, being one more than the number of dimensions.

Two important characteristics are lifetime, which tends to increase in relation to mass raised to the power of 1/4, and heart rate, which is associated with mass raised to the power of -1/4. If you multiply the two together to obtain the total number of heartbeats, the 1/4 and the -1/4 cancel each other out, leaving you with a constant of around 1.5 billion.

Human heart beats

According to the NHS, the normal adult heart rate while resting is 60 to 100 bpm, but fitter people have lower heart rates, with athletes having rates of 40 to 60 bpm. Suppose we compare Lazy Larry, whose resting heart rate is 70bpm, with Sporty Steve, who has the same body mass, but has a resting heart rate of 50bpm.

Let’s assume that as Larry eats, drinks coffee and moves around, his average heart rate across the day is 80bpm. Steve carries out the same activities, but he also follows a weekly training plan of that involves periods of elevated heart rates. During exercise Steve’s heart beats at 140bpm for an average of one hour a day, but the rest time it averages 60bpm.

If Larry expects to live until he is 80, he would have 80*60*24*365*80 or 3.36 billion heart beats. This is higher than West’s figure of 1.5 billion, but before the advent of modern hygiene and medicine, it would not be unusual for humans to die by the age of 40.

Exercise is good for you

The key message is that, accounting for exercise, Steve’s average daily heart rate is (140*1+60*23)/24 or 63bpm. The benefits of having a lower heart rate than Larry easily offset the effects of one hour of daily vigorous exercise.

Although it is a rather silly exercise, one could ask how long Steve would live if he expected the same number of heartbeats as Larry. The answer is 80/63 times longer or 101 years. So if mortality were determined only by the capacity of the heart to beat a certain number of times, taking exercise could add 21 years to a lifetime. Before entirely dismissing that figure, note that NHS data show that ischaemic heart disease remains one of the leading causes of death in the UK. Cardiac health is a very important aspect of overall health.

Obviously many other factors affect longevity, for example those taking exercise tend to be more aware of their health and are less likely to suffer from obesity, smoke, consume excessive alcohol or eat ultra-processed foods.

A study of 4,082 Commonwealth Games medallists showed that male athletes gained between 4.5 and 5.3 extra years of life and female athletes 3.9. Although cycling was the only sport that wasn’t associated with longer lives, safety has improved and casualty rates have declined over the years.

Exercise, good nutrition and sufficient sleep are crucial for health and longevity. There’s no point in waiting until you are 60 and taking elixirs and magic potions. The earlier in life you adopt good habits, the longer you are likely to live.

Fuelling your rides on Strava

As we move into our 40s, 50s and beyond, we may become aware of changes in our bodies. Performance peaks level off or start to decline. Even if you don’t feel old, it becomes harder to keep up with younger sprinters. It takes longer to recover from a hard ride, injury or illness.

Muscle, Fat and Bone

The cause of these age-related changes is a decline in the production of specific hormones. Growth hormone falls insidiously from the time we reach adult height. From the age of 50, testosterone levels drop slightly in men, while oestradiol levels fall dramatically as women reach menopause. The key thing to note about growth hormone and testosterone is that they are anabolic agents, i.e. they build muscle. As they decline, there is a tendency to lose muscle and to increase fat deposition. Sex steroids also play a pivotal role in bone formation.

Protein, Carbohydrates and Vitamin D

Fortunately there are measures we can take to counter the effects of declining hormones. Nutrition plays an important role. Understanding the physiological effects of hormonal changes makes it easier to recognise beneficial adaptations in your diet.

Protein provides the building blocks required for muscle. Taking an adequate level of protein, spread out through the day, is beneficial.

Carbohydrates are the key fuel for moderate to high intensity. Fasted training is not advisable. The body’s shock reaction to underfuelled training is to deposit fat.

The UK government advises everyone to take vitamin D supplements, especially over the winter. In addition to supporting bone health, studies have shown improved immunity and muscle recovery.

Nutrition, Exercise and Recovery

When combined with adequate nutrition, exercise, particularly strength training, stimulates the production of growth hormone and testosterone. It is important to ensure adequate recovery and to follow a regular routine of going to be early, because these hormones are produced while you are asleep.

Everybody is unique, so you need to work out what works best for you. For further insights on this topic, Dr Nicky Keay has written a book full of top tips, called Hormones Health and Human Potential.

Generating music videos using Stable Diffusion

Video generated using Stable Diffusion

In my last post I described how to generate a series of images by feeding back the output of a Stable Diffusion image-to-image model as the input for the next image. I have now developed this into a Generative AI pipeline that creates music videos from the lyrics of songs.

Learning to animate

In my earlier blog about dreaming of the Giro, I saved a series of key frames in a GIF, resulting in an attractive stream of images, but the result was rather clunky. The natural next step was to improve the output by inserting frames to smooth out the transitions between the key frames, saving the result as a video in MP4 format, at a rate of 20 frames per second.

I started experimenting with a series of prompts, combined with the styles of different artists. Salvador Dali worked particularly well for dreamy animations of story lines. In the Dali example below, I used “red, magenta, pink” as a negative prompt to stop these colours swamping the image. The Kandinsky and Miro animations became gradually more detailed. I think these effects were a consequence of the repetitive feedback involved in the pipeline. The Arcimboldo portraits go from fish to fruit to flowers.

Animations in the styles of Dali, Kandinsky, Miro and Arcimboldo

Demo app

A created a demo app on Hugging Face called AnimateYourDream. In order to get this to work, you need to duplicate it and then run it using a GPU on your Hugging Face account (costing $0.06 per hour). The idea was to try to recreate a dream I’d had the previous night. You can choose the artistic style, select an option to zoom in, enter three guiding prompts with the desired number of frames and choose a negative prompt. The animation process takes 3-5 minutes on a basic GPU.

For example, setting the style as “Dali surrealist”, zooming in, with 5 frames each of “landscape”, “weird animals” and “a castle with weird animals” produced the following animation.

Demo of my AnimateYourDream app on Hugging Face

Music videos

After spending some hours generating animations on a free Google Colab GPU and marvelling over the animations, I found that the images were brought to life by the music I was playing in the background. This triggered the brainwave of using the lyrics of songs as prompts for the Stable Diffusion model.

In order to produce an effective music video, I needed the images to change in time with the lyrics. Rather than messing around editing my Python code, I ended up using a Excel template spreadsheet as a convenient way to enter the lyrics alongside the time in the track. It was useful to enter “text” as a negative prompt and a sometimes helpful to mention a particular colour to stop it dominating the output. By default an overall style is added to each prompt, but it is convenient to change the style on certain prompts. By default the initial image is used as a “shadow”, which contributes 1% to every subsequent frame, in an attempt to retain an overall theme. This can also be overridden on each prompt.

Finally, it was very useful to be able to define target images. If defined for the initial prompt, this saves loading an additional Stable Diffusion text-to-image pipeline to create the first frame. Otherwise, defining a target image for a particular prompt drags the animation towards the target, by mixing increasing proportions of the target with the current image, progressively from the previous prompt. This is also useful for the final frame of the animation. One way to create target images is to run a few prompts through Stable Diffusion here.

Although some lyrics explicitly mention objects that Stable Diffusion can illustrate, I found it helps to focus on specific key words. This is my template for “No more heroes” by The Stranglers. It produced an awesome video that I put on GitHub.

Once an Excel template is complete, the following pipeline generates the key frames by looping through each prompt and calculating how many frames are required to fill the time until the next prompt for the desired seconds per frame. A basic GPU takes about 3 seconds per key frame, so a song takes about 10-20 minutes, including inserting a smoothing steps between the key frames.

Sample files and a Jupyter notebook are posted on my GitHub repository.

I’ve started a YouTube channel

Having previously published my music on SoundCloud, I am now able to generate my own videos. So I have set up a YouTube channel, where you can find a selection of my work. I never expected the fast.ai course to lead me here.

PyData London

I presented this concept at the PyData London – 76th meetup on 1 August 2023. These are my slides.

[office src="https://onedrive.live.com/embed?resid=2043474D20AC7A6F%21321&authkey=!ADzwAz1VEcCPgi4&em=2" width="402" height="327"]

Dreaming of the Giro

fast.ai’s latest version of Practical Deep Learning for Coders Part 2 kicks off with a review of Stable Diffusion. This is a deep neural network architecture developed by Stability AI that is able to convert text into images. With a bit of tweaking it can do all sorts of other things. Inspired by the amazing videos created by Softology, I set out to generate a dreamlike video based on the idea of riding my bicycle around a stage of the Giro d’Italia.

Text to image

As mentioned in a previous post, Hugging Face is a fantastic resource for open source models. I worked with one of fast.ai’s notebooks using a free GPU on Google Colab. In the first step I set up a text-t0-image pipeline using a pre-trained version of stable-diffusion-v1-4. The prompt “a treelined avenue, poplars, summer day, france” generated the following images, where model was more strongly guided by the prompt in each row. I liked the first image in the second row, so I decided to make this the first frame in an initial test video.

Stable diffusion is trained in a multimodal fashion, by aligning text embeddings with the encoded versions corresponding images. Starting with random noise, the pixels are progressively modified in order to move the encoding of the noisy image closer to something that matches the embedding of the text prompt.

Zooming in

The next step was to simulate the idea of moving forward along the road. I did this by writing a simple two-line function, using fast.ai tools, that cropped a small border off the edge of the image and then scaled it back up to the original size. In order to generate my movie, rather that starting with random noise, I wanted to use my zoomed-in image as the starting point for generating the next image. For this I needed to load up an image-to-image pipeline.

I spent about an hour experimenting with with four parameters. Zooming in by trimming only a couple of pixels around the edge created smoother transitions. Reducing the strength of additional noise enhanced the sense of continuity by ensuring that that subsequent images did not change too dramatically. A guidance scale of 7 forced the model to keep following prompt and not simply zoom into the middle of the image. The number of inference steps provided a trade-off between image quality and run time.

When I was happy, I generated a sequence of 256 images, which took about 20 minutes, and saved them as a GIF. This produced a pleasing, constantly changing effect with an impressionist style.

Back to where you started

In order to make the GIF loop smoothly, it was desirable to find a way to return to the starting image as part of the continuous zooming in process. At first it seemed that this might be possible by reversing the existing sequence of images and then generating a new sequence of images using each image in the reversed list as the next starting point. However, this did not work, because it gave the impression of moving backwards, rather than progressing forward along the road.

After thinking about the way stable diffusion works, it became apparent that I could return to the initial image by mixing it with the current image before taking the next step. By progressively increasing the mixing weight of the initial image, the generated images became closer to target over a desired number of steps as shown below.

Putting it al together produced the following video, which successfully loops back to its starting point. It is not a perfect animation, because the it zooms into the centre, whereas the vanishing point is below the centre of the image. This means we end up looking up at the trees at some points. But overall it had the effect I was after.

A stage of the Giro

Once all this was working, it was relatively straightforward to create a video that tells a story. I made a list of prompts describing the changing countryside of an imaginary stage of the Giro d’Italia, specifying the number of frames for each sequence. I chose the following.

[‘a wide street in a rural town in Tuscany, springtime’, 25],

[‘a road in the countryside, in Tuscany, springtime’,25],

[“a road by the sea, trees on the right, sunny day, Italy”,50],

[‘a road going up a mountain, Dolomites, sunny day’,50],

[‘a road descending a mountain, Dolomites, Italy’,25],

[‘a road in the countryside, cypress trees, Tuscany’,50],

[‘a narrow road through a medieval town in Tuscany, sunny day’,50]

These prompts produced the video shown at the top of this post. The springtime blossom in the starting town was very effective and the endless climb up into the sunlit Dolomites looked great. For some reason the seaside prompt did not work, so the sequence became temporarily stuck with red blobs. Running it again would make something different. Changing the prompts offered endless possibilities.

The code to run this appears on my GitHub page. If you have a Google account, you can open it directly in Colab and set the RunTime to GPU. You also need a free Hugging Face account to load the stable diffusion pipelines.

Percolating Python with ChatGPT

A YouTube video about “percolation” includes an interesting animation of shifting colours that exhibits a sudden phase transition. As a challenge, I set out to replicate the evolving pattern in Python. But then I remembered hearing that ChatGPT was good at writing code, so I asked it for help

Percolation

Percolation models can be used to simulate physical systems, such as liquids permeating through porous materials. The idea is to take a grid pattern of nodes with edges between them, and then remove edges at random. Each edge survives with a probability, p. If the edges were pipes, we could imagine that water could percolate through a well-connected grid (image on the left), but, as more edges are removed, the nodes form connected islands that prevent onward percolation (image on the right).

Asking ChatGPT

I started by asking ChatGPT to model a randomly connected lattice in Python. It suggested using a library called networkx that I have used in the past, so I pasted the code into a Jupyter notebook. The code worked, but the nodes were scattered at random, so I asked ChatGPT for code to produce a regular grid. This failed, so I passed the error message back to ChatGPT, which explained the problem and suggested revised code that worked perfectly, producing something like the left hand image above.

The next step was to apply the same colour to all connected nodes. Initially I called these clusters, but then I discovered that networkx has a method called connected_components, so I substituted this into ChatGPT’s code. After about half an hour, I had added more colours and some ipywidget sliders, to produce a fully working interactive model, where I could vary p and adjust the size of the grid.

The really interesting behaviour happens when p is around 0.5. Below this value the grid tends to form a disjoint set of unconnected islands, but above the critical value, the large areas quickly connect up. This image at the top of this blog occurs around the middle of the video below.

Percolation Model

Python code

This is the code if you want to try it yourself. You might need to pip install networkx and ipywidgets.

import networkx as nx
import numpy as np
import matplotlib.pyplot as plt
import random
from ipywidgets import interact

def randomLattice(p=0.5, n = 100):
    # Square grid m=n
    m=n
    # Create a 2D grid of nodes using NumPy
    nodes = np.array([(i, j) for i in range(m) for j in range(n)])

    # Convert the NumPy array to a list of tuples
    nodes = [tuple(node) for node in nodes]

    # Create an empty graph
    G = nx.Graph()

    # Add nodes to the graph
    G.add_nodes_from(nodes)

    # Connect adjacent nodes horizontally
    for i in range(m):
        for j in range(n-1):
            if random.random() < p:  # adjust the probability to control the connectivity
                G.add_edge((i, j), (i, j+1))

    # Connect adjacent nodes vertically
    for i in range(m-1):
        for j in range(n):
            if random.random() < p:  # adjust the probability to control the connectivity
                G.add_edge((i, j), (i+1, j))


    clusters = list(nx.connected_components(G))
    colours = ["b", "r", "g", "y", "m", "c", "k",'lime','cyan','violet','gold','indigo','navy','grey','peru']
    node_to_colour = {}
    for i, cluster in enumerate(clusters):
        for node in cluster:
            node_to_colour[node] = colours[i%len(colours)]
    #print(clusters)
    # Draw the graph as a regular grid
    pos = dict(zip(nodes, nodes))
    nx.draw(G, pos=pos, node_color=[node_to_colour[i] for i in nodes], 
            with_labels=False,node_size=20)
    #plt.savefig(f'Grid_{int(p*100):03d}.png')
    plt.show()
    return


interact(randomLattice,p=(0,1,0.01), n = (5,200,1));

Sword in the stone

The project began by building the sword from scratch. Following a series of clearly explained steps, a basic cube was stretched and reshaped until it took the form of a blade. Adding a metallic material complete with subtle scratches and blemishes enhanced its realism. Clever use of mirror symmetry ensured that the handle and pommel were perfectly balanced. The handle was decorated a leather texture. In the next step the blade and pommel were imbued with light emitting runes.

The sword was embedded in some rocks designed to look like a plinth with two small steps. The rock were positioned to create leading lines towards the sword handle. A rocky background gave the impression of being inside a cave. This was achieved by randomly scattering rocks onto the tessellated faces of a partial hemisphere and fiddling with the density parameter.

Although Blender includes a range of particle simulators, this project used geometry nodes to create the flames, embers and floating particles, adding dramatic effect to the sword.

Having constructed the elements of the scene, considerable time was spent on lighting and volumetric effects, with the aim of creating depth and realism. For example, randomly positioning shapes, called gobos, in front of the spotlights created patches of light and shade in the beams, helping to highlight important elements, like the handle of the sword. Making the spotlights the children of their targets ensured that they moved synchronously. Another step, called compositing, was used to generate an ethereal vignette and adjust the colour balance between foreground and background.

The next step introduced cameras to create the final animation. Once the key frames were positioned in the dope sheet, Blender automatically panned the camera around the scene. Further spectacle was added to the setting by importing a free motion captured character from the fantastic Mixamo site.

Having completed the tutorial, I extended the animation, slowed it down to half speed and added some of my own music to produce the final video. One of the reasons for embarking on the project was to test out the power of the GPUs on my new MacBook Pro. It did not disappoint, rendering the entire video at lightning speed.

In a future project, I plan to experiment with Blender’s Python API.

Hugging Face

I have been blown away exploring Hugging Face. It’s a community on a mission “to democratize good machine learning”. It provides access to a huge library of state-of-the-art models. So far I have only scratched the surface of what is available, but this blog gives a sample of things I have tried.

At the time of writing, there were 128,463 pre-trained models covering a huge range of capabilities, including computer vision, natural language processing, audio, tabular, multimodal and reinforcement models. The site is set up to make it incredibly easy to experiment with a demo, download a model, run it in a Jupyter notebook, fine-tune it for a specific task and then add it to the space of machine learning apps created by the community. For example, an earlier blog describes my FilmStars app.

Computer vision with text

This is an example from an app that uses the facebook/detr-resnet-50 model to identify objects in an image. It successfully located eight objects with high confidence (indicated by the numbers), but it was fooled into thinking part of the curved lamppost in front of the brickwork pattern was a tennis racket (you can see why).

Image-to-text models go further by creating captions describing what is in the image. I used an interactive demo to obtain suggested captions from a range of state-of-the-art models. The best result was produced by the GIT-large model, whereas a couple of models perceived a clocktower .

These models can also answer questions about images. Although all of the answers were reasonable, GIT-large produced the best response when I asked “Where is the cyclist?”

The next image is an example of text-based inpainting with CLIPSeg x Stable Diffusion, where I requested that wall should be replaced with an apartment block. The model successfully generated a new image while preserving the cyclist, flowers, arch, background and even the birds on the roof. I had great fun with this app, imagining what my friend’s house will look like, when it eventually emerges from a building site.

Continuing with the theme of image generation, I reversed the image to caption problem, by asking a stable-diffusion-v1-5 model to generate an image from the caption “a cyclist rides away through an old brick archway in a city”. It came up with an image remarkably similar to what we started with, even including a female cyclist.

Do it yourself

HuggingFace provides various ways for you to download any of the models from its library. The easiest way to do this is to set up a free account on kaggle, which offers a Jupyter notebook environment with access to a GPU.

Using a HuggingFace pipeline, you can run a model with three lines of Python code! Pipelines can be set up for the image models above, but this is an example of the code required to run a text-based natural language processing task. It creates and runs a pipeline that summarises text, using a model specifically trained to generate output in the style of SparkNotes.

from transformers import pipeline
summarizer = pipeline("summarization",model="pszemraj/long-t5-tglobal-base-16384-book-summary")
summarizer("""Sample text from a book...""")

This rather morbid sample text produced the output from Python that follows.

The fact that Henry Armstrong was buried did not seem to him to prove that he was dead: he had always been a hard man to convince. That he really was buried, the testimony of his senses compelled him to admit. His posture — flat upon his back, with his hands crossed upon his stomach and tied with something that he easily broke without profitably altering the situation — the strict confinement of his entire person, the black darkness and profound silence, made a body of evidence impossible to controvert and he accepted it without cavil.

But dead — no; he was only very, very ill. He had, withal, the invalid’s apathy and did not greatly concern himself about the uncommon fate that had been allotted to him. No philosopher was he — just a plain, commonplace person gifted, for the time being, with a pathological indifference: the organ that he feared consequences with was torpid. So, with no particular apprehension for his immediate future, he fell asleep and all was peace with Henry Armstrong.

But something was going on overhead. It was a dark summer night, shot through with infrequent shimmers of lightning silently firing a cloud lying low in the west and portending a storm. These brief, stammering illuminations brought out with ghastly distinctness the monuments and headstones of the cemetery and seemed to set them dancing. It was not a night in which any credible witness was likely to be straying about a cemetery, so the three men who were there, digging into the grave of Henry Armstrong, felt reasonably secure.
From One Summer Night by Ambrose Bierce

[{'summary_text': "Henry's body is buried in the cemetery, but it does not seem to make him any more certain that he is dead. Instead, he seems to be completely ill."}]

Having come this far, it takes only a few steps to fine tune the model to match your desired task, put it into a GitHub repository and launch your own app as a fully fledged member of the Hugging Face community. A nice explanation is available at fast.ai lesson 4.

Active Inference

Active Inference is a fascinating and ambitious book. It describes a very general normative approach to understanding the mind, brain and behaviour, hinting at potential applications in machine learning and the social sciences. The authors argue that the ways in which living beings interact with the environment can be modelled in terms of something called the free energy principle.

Active Inference builds on the concept of a Bayesian Brain. This is the idea that our brains continually refine an internal model of the external world, acting as probabilistic inference machines. The internal generative model continually predicts the state of the environment and compares its predictions with the inputs of sensory organs. When a discrepancy occurs, the brain updates its model. This is called perception.

But Active Inference goes further my recognising that living things can interact with their environments. Therefore an alternative way to deal with a discrepancy versus expectations is to do something that modifies the world. This is called action.

Variational Free Energy

Active Inference, Parr, Pezzulo, Friston

Either you change your beliefs to match the world or you change the world to match your beliefs. Active Inference makes this trade off by minimising variational free energy, which improves the match between an organism’s internal model and the external world.

The theory is expressed in elegant mathematical terms that lend themselves to systematic analysis. Minimising variational free energy can be considered in terms of finding a maximum entropy distribution, minimising complexity or reducing the divergence between the internal model and the actual posterior distribution.

Expected free energy

Longer term planning is handled in terms of expected free energy. This is where the consequences of future sequences of actions (policies) are evaluated by predicting the outcomes at each stage. The expected free energy of each policy is converted into a score, with the highest score determining the policy the organism expects to pursue. The process of selecting policies that improve the match with the priors pertaining to favoured states is called learning.

Planning is cast in terms of Bayesian inference. Once again the algebraic framework lends itself to a range of interpretations. For example, it automatically trades off information gain (exploration) against pragmatic value (exploitation). This contrasts with reinforcement learning, which handles the issue more heuristically, by trial and error, combined with the notion of a reward.

Applications

The book describes applications in neurobiology, learning and perception. Although readers are encouraged to apply the ideas to new areas, a full understanding of the subject demands the dedication to battle through some heavy duty mathematical appendices, covering Bayesian inference, partially observed Markov Decision Processes and variational calculus.

Nevertheless the book is filled with thought provoking ideas about how living things thrive in the face of the second law of thermodynamics.