Part IA Flood Monitoring and Warning System¶
Lent Term 2024, Department of Engineering, University of Cambridge
Your team has been tasked with building the computational backend (library) to a new real-time flood warning system for England. The library should:
Fetch real-time river level data over the Internet from the Department for Environment Food and Rural Affairs data service.
Support specified data query types on river level monitoring stations.
Analyse monitoring station data in order to assess flood risks, and issue flood warnings for areas of the country.
The mandated development practices are listed in the Requirements section. The library is required to support specific query interfaces (API), as outlined in the Deliverables section, which form the public interface of the library. Another company has been contracted to build a user interface using the prescribed public interfaces to the library, hence they cannot be changed.
Development team
Your development team is your laboratory group.
Requirements¶
This section defines the technical requirements for the implementation.
Language and library structure¶
Library is to be developed in Python 3 and using multiple modules (files). Each file should collect related functionality.
Documentation¶
All classes, methods (a function that belongs to a class) and functions must be documented with a ‘docstring’. The docstring shall explain what the class or function does. For a function, the docstring shall make clear the purpose, what arguments are expected and what is returned.
Simple examples of Python docstrings can be viewed here.
Development practices¶
The quality of a flood warning software library is paramount; implementation errors could put lives at risk and lead to substantial financial losses. You are therefore required to adopt software engineering best practices. Your team is required to:
Provide automated tests for your implementations using pytest to demonstrate the quality of the system (see Test framework)
Use automated continuous integration testing (see Automated testing)
Data source¶
The system is to be built on the (near) real-time river level data at the nearly 2000 monitoring stations that is made available by the Department for Environment Food and Rural Affairs (DEFRA) at https://environment.data.gov.uk/. For most stations river level data is updated every 15 minutes. The data service is summarised at https://data.gov.uk/dataset/real-time-and-near-real-time-river-level-data1.
- REST interface for data retrieval
Data is fetched from https://environment.data.gov.uk/ using a REST interface. With a suitably formed URL (a string), as defined in the service documentation, the server returns the requested data as a JSON object. JSON objects are represented in Python as data structures made up of dictionaries, lists and strings. JSON objects are straightforward to manipulate from Python. The interface to the DEFRA service is documented at https://environment.data.gov.uk/flood-monitoring/doc/reference.
Deliverables¶
This section defines the project deliverables. Functionality is to be
implemented in the module named floodsystem
.
Milestones and deadlines
Project deliverables/tasks are structured into two milestones. Milestone 1 must be delivered by the interim marking session, and Milestone 2 by the final marking session. You may deliver early by signing off at the Help Desk.
Clarifications
Clarifications can be sought at the Help Desk.
Task completion, interfaces and demonstration programs
Each task requires the implementation of functionality that can be accessed via a specified interface, usually a function signature (function name and arguments, and return values). At the end of each task is a description of a demonstration program that must be be provided. Demonstration programs must have the structure:
def run():
# Put code here that demonstrates functionality
if __name__ == "__main__":
run()
You should expect to run demonstration programs during a marking session.
Important
Conforming to the specified public interface is critical as this will allow the interface team to work independently of your development (and it will allow automated testing of your work).
Testing
Write tests as you progress through the tasks (see Test framework) and add deliverables and tests to the automated testing system (see Automated testing).
Tip
To deliver on a Task, you will often want to implement more functions than just the required function interface. Use additional functions to:
Modularise and simplify your library.
Allow re-use of functions across tasks.
Simplify testing.
As you work through the Tasks, look for opportunities to re-structure code in order to re-use functions.
Milestone 1¶
Processing of monitoring station properties.
- Deadline:
Mid-term sign-up session
- Points:
4
Caution
Do not use the ‘representative output’ in your pytest tests. Representative output is provided to help you, but would not be part of a real contract. Moreover, you are working with real-time data which will change.
Task 1A: build monitoring station data¶
This task has been completed for you in the template repository.
In a submodule
station
, create a classMonitoringStation
that represents a monitoring station, and has attributes:Station ID (
string
)Measurement ID (
string
)Name (
string
)Geographic coordinate (
tuple(float, float)
)Typical low/high levels (
tuple(float, float)
)River on which the station is located (
string
)Closest town to the station (
string
)
Implement the methods
__init__
to initialise a station with data, and__repr__
for printing a description of the station.In the submodule
stationdata
implement a function that returns a list ofMonitoringStation
objects (for active stations with water level monitoring). To avoid excessive data requests, the function should save fetched data to file, and then optionally read from a cache file. The function should have the signature:def build_station_list(use_cache=True):
The data should be retrieved from the online service documented at http://environment.data.gov.uk/flood-monitoring/doc/reference.
Task 1B: sort stations by distance¶
In the submodule
geo
implement a function that, given a list of station objects and a coordinate p, returns a list of(station, distance)
tuples, wheredistance
(float
) is the distance of thestation
(MonitoringStation
) from the coordinate p. The returned list should be sorted by distance. The required function signature is:def stations_by_distance(stations, p):
where
stations
is a list ofMonitoringStation
objects andp
is a tuple of floats for the coordinate p.
Tip
The distance between two geographic coordinates (latitude/longitude) is computed using the haversine formula. You could program the haversine formula, or you could use a Python library to perform the computation for you, e.g. https://pypi.org/project/haversine/.
Hint
Build a list of all
(station, distance)
tuples, and use the provided functionutils.sort_by_key
to produce a list that is sorted by the second entry in the tuple.
Task 1C: stations within radius¶
In the submodule
geo
implement a function that returns a list of all stations (typeMonitoringStation
) within radius r of a geographic coordinate x. The required function signature is:def stations_within_radius(stations, centre, r):
where
stations
is a list ofMonitoringStation
objects,centre
is the coordinate x andr
is the radius.
Task 1D: rivers with a station(s)¶
In the submodule
geo
develop a function that, given a list of station objects, returns a container (list
/tuple
/set
) with the names of the rivers with a monitoring station. The function should have the signature:def rivers_with_station(stations):
where
stations
is a list ofMonitoringStation
objects. The returned container should not contain duplicate entries.In the submodule
geo
implement a function that returns a Pythondict
(dictionary) that maps river names (the ‘key’) to a list of station objects on a given river. The function should have the signature:def stations_by_river(stations):
where
stations
is a list ofMonitoringStation
objects.
Task 1E: rivers by number of stations¶
Implement a function in
geo
that determines the N rivers with the greatest number of monitoring stations. It should return alist
of (river name, number of stations) tuples, sorted by the number of stations. In the case that there are more rivers with the same number of stations as the N th entry, include these rivers in the list. The function should have the signature:def rivers_by_station_number(stations, N):
where
stations
is a list ofMonitoringStation
objects.
Task 1F: typical low/high range consistency¶
It is suspected that some stations have inconsistent data for typical low/high ranges, namely that (i) no data is available; or (ii) the reported typical high range is less than the reported typical low. This needs to be checked so that stations with inconsistent data are not used erroneously in flood warning analysis.
Add a method to the
MonitoringStation
class that checks the typical high/low range data for consistency. The method should returnTrue
if the data is consistent andFalse
if the data is inconsistent or unavailable. The method should have the signature:def typical_range_consistent(self):
Implement in the submodule
station
a function that, given a list of station objects, returns a list of stations that have inconsistent data. The function should useMonitoringStation.typical_range_consistent
, and should have the signature:def inconsistent_typical_range_stations(stations):
where
stations
is a list ofMonitoringStation
objects.
Optional extensions¶
Display the location of each station on a map (perhaps from Google Maps). Suitable Python libraries tools for this include Bokeh and Plotly.
Explore what other station information is available in the retrieved data. The function
stationdata.build_station_list
is a good place to start. ExtendMonitoringStation
to store any interesting station data as attributes.Advanced: The
MonitoringStation
attributes (station data) are properties of the station and will not generally change. However, we could accidentally and mistakenly change an attribute in our code. For flood forecasting and warning, such an error could have dire consequences. Use property decorators to prevent accidental modification of the attributes.
Milestone 2¶
The focus of the Milestone 2 is processing monitoring station real-time data to warn of flood risks.
- Deadline:
End-of-term sign-up session
- Points:
8
Caution
Representative output for each demonstration program is provided as a guide. You will be working with real-time data, so the precise output will change with time.
Task 2A: fetch real-time river levels¶
This task has been completed for you in the template repository.
Extend the
MonitoringStation
class with an attributelatest_level
(float
), and implement in thestationdata
submodule a function that updates the latest water level for all stations in a list using data fetched from the Internet. If level data is not available, the attributelatest_level
should be set toNone
. The function should have the signature:def update_water_levels(stations):
where
stations
is a list ofMonitoringStation
objects.
Task 2B: assess flood risk by level¶
Add a method to
MonitoringStation
that the returns the latest water level as a fraction of the typical range, i.e. a ratio of 1.0 corresponds to a level at the typical high and a ratio of 0.0 corresponds to a level at the typical low. The method should have the signature:def relative_water_level(self):
If the necessary data is not available or is inconsistent, the function should return
None
.In the submodule
flood
, implement a function that returns a list of tuples, where each tuple holds (i) a station (object) at which the latest relative water level is overtol
and (ii) the relative water level at the station. The returned list should be sorted by the relative level in descending order. The function should have the signature:def stations_level_over_threshold(stations, tol):
where
stations
is a list ofMonitoringStation
objects. Consider only stations with consistent typical low/high data.
Task 2C: most at risk stations¶
Implement a function in the submodule
flood
that returns a list of the N stations (objects) at which the water level, relative to the typical range, is highest. The list should be sorted in descending order by relative level. The function should have the signature:def stations_highest_rel_level(stations, N):
where
stations
is a list ofMonitoringStation
objects.
Task 2D: level data time history¶
This task has been completed for you in the template repository.
Implement in the submodule
datafetcher
a function that retrieves from the Internet the water level data for a given station ‘measure id’ over the period from the current time back to d days ago. It should return a tuple with the first entry being the sample times and the second entry being the water levels. The function should have the signature:def fetch_measure_levels(measure_id, dt):
Typical use to retrieve the level data at a station over the past 10 days would be:
import datetime dt = 10 dates, levels = fetch_measure_levels(station.measure_id, dt=datetime.timedelta(days=dt))
Task 2E: plot water level¶
Implement in a submodule
plot
a function that displays a plot (using Matplotlib) of the water level data against time for a station, and include on the plot lines for the typical low and high levels. The axes should be labelled and use the station name as the plot title. The function should have the signature:def plot_water_levels(station, dates, levels):
where
station
is aMonitoringStation
object.Hint
Example code to display a plot using Matplotlib:
import matplotlib.pyplot as plt from datetime import datetime, timedelta t = [datetime(2016, 12, 30), datetime(2016, 12, 31), datetime(2017, 1, 1), datetime(2017, 1, 2), datetime(2017, 1, 3), datetime(2017, 1, 4), datetime(2017, 1, 5)] level = [0.2, 0.7, 0.95, 0.92, 1.02, 0.91, 0.64] # Plot plt.plot(t, level) # Add axis labels, rotate date labels and add plot title plt.xlabel('date') plt.ylabel('water level (m)') plt.xticks(rotation=45); plt.title("Station A") # Display plot plt.tight_layout() # This makes sure plot does not cut off date labels plt.show()
Optional: In place of Matplotlib, try using a web-centric plotting library such as Bokeh or Plotly.
Optional extension: Generalise your implementation such that it takes a list of up to 6 stations displays the level at each station as subplot inside a single plot.
Task 2F: function fitting¶
In a submodule
analysis
implement a function that given the water level time history (dates, levels) for a station computes a least-squares fit of a polynomial of degree p to water level data. The function should return a tuple of (i) the polynomial object and (ii) any shift of the time (date) axis (see below). The function should have the signature:def polyfit(dates, levels, p):
Typical usage for a polynomial of degree 3 would be:
poly, d0 = polyfit(dates, levels, 3)
where
poly
is a numpy.poly1d object and0
is any shift of the date (time) axis.Hint
To work with dates as function arguments, e.g. a polynomial that depends on time, the dates need to be converted to floats. Matplotlib has a function date2num that from a list of
datetime
objects returns a list offloat
, where the floats are the time in days (including fractions of days) since the year 0001:import matplotlib x = matplotlib.dates.date2num(dates)
Hint
NumPy has tools for computing least-squares fits to data. The below example computes a least-squares fit for some data points, and plots the data points and the least-squares polynomial:
import numpy as np import matplotlib.pyplot as plt # Create set of 10 data points on interval (0, 2) x = np.linspace(0, 2, 10) y = [0.1, 0.09, 0.23, 0.34, 0.78, 0.74, 0.43, 0.31, 0.01, -0.05] # Find coefficients of best-fit polynomial f(x) of degree 4 p_coeff = np.polyfit(x, y, 4) # Convert coefficient into a polynomial that can be evaluated, # e.g. poly(0.3) poly = np.poly1d(p_coeff) # Plot original data points plt.plot(x, y, '.') # Plot polynomial fit at 30 points along interval x1 = np.linspace(x[0], x[-1], 30) plt.plot(x1, poly(x1)) # Display plot plt.show()
Caution
In the above example, if we changed the
x
interval (0, 2) to (10000, 10002), i.e.:x = np.linspace(10000, 10002, 10)
NumPy prints the warning message:
RankWarning: Polyfit may be poorly conditioned warnings.warn(msg, RankWarning)
This message is warning that floating point round-off errors will be significant and will affect accuracy. In simple terms, the issues is that when we raise a number between 10000 and 10002 to a power, small but important differences are effectively ‘lost’.
This issues arises if we work with dates converted to floats using
matplotlib.dates.date2num
since it returns the number of days since the origin of the Gregorian calendar. The numbers will therefore be large. A way to improve the situation is with a change-of-variable:import numpy as np import matplotlib.pyplot as plt # Create set of 10 data points on interval (1000, 1002) x = np.linspace(10000, 10002, 10) y = [0.1, 0.09, 0.23, 0.34, 0.78, 0.74, 0.43, 0.31, 0.01, -0.05] # Using shifted x values, find coefficient of best-fit # polynomial f(x) of degree 4 p_coeff = np.polyfit(x - x[0], y, 4) # Convert coefficient into a polynomial that can be evaluated # e.g. poly(0.3) poly = np.poly1d(p_coeff) # Plot original data points plt.plot(x, y, '.') # Plot polynomial fit at 30 points along interval (note that polynomial # is evaluated using the shift x) x1 = np.linspace(x[0], x[-1], 30) plt.plot(x1, poly(x1 - x[0])) # Display plot plt.show()
In the submodule
plot
, add a function that plots the water level data and the best-fit polynomial. The function must have the signature:def plot_water_level_with_fit(station, dates, levels, p):
where
station
is aMonitoringStation
object.
Caution
Fitting high-degree polynomials to data is notoriously tricky, especially if the data is not very smooth (as will often be the case with water level data). The problem is that oscillations can appear at the ends of the interval. The is known as Runge’s phenomenon. You can observe this with the river level data by increasing the polynomial degree, say to 10, and the time interval, say to 10 days.
Task 2G: issuing flood warnings for towns¶
Using your implementation, list the towns where you assess the risk of flooding to be greatest. Explain the criteria that you have used in making your assessment, and rate the risk at ‘severe’, ‘high’, ‘moderate’ or ‘low’.
Note
This task is an opportunity to demonstrate your creativity and technical insights.
Tip
Consider how you could forecast whether the water level at a station is rising or falling.
Optional extensions¶
Show all stations on a map, and indicate by colour stations that are (i) below the typical range; (ii) within the typical range; (iii) above the typical range; or (iv) for which there is not level data.
Provide a web-based interface to your flood warning system.
Incorporate rainfall data from http://environment.data.gov.uk/flood-monitoring/doc/reference into your system.
Explore what other data from http://environment.data.gov.uk/flood-monitoring/doc/reference you could use to improve your monitoring and warning system. To start, examine the data that is already being retrieved but has not been used.
Getting started¶
Read the Requirements section.
Install, configure and test your development environment (Development environment).
Create a Git repository for your team/project (Creating a team development repository) from the provided template.
Read Using Git.
Read the Deliverables section, and with your team consider dependencies between ‘tasks’ in the deliverables and allocate independent tasks to a team member (Project planning).
Start implementing your tasks (Editing and executing Python code).
Tip
Start simple and work in small steps. It is much easier to add functionality to a working program than to fix a complicated non-working program.
Note
When developing your programs, you may need to review the activity notebooks from Michaelmas Term.
Development environment¶
Note
Experienced developers have their preferred tools and development environments. If you are experienced with Git, Python and using editors, you are free to use your preferred tools.
The following procedures and tools are suggested.
Option 1: Web-based environment¶
You can use GitHub Codespaces, which provides a development environment in your browser.
Option 2: Local software installation¶
Install Visual Studio Code (https://code.visualstudio.com/).
Visual Studio Code will provide instructions on how to install
git
andpython
when you need them. Otherwise, instructions at https://code.visualstudio.com/docs/sourcecontrol/overview and https://code.visualstudio.com/docs/languages/python.
Testing your Python installation¶
Create a file in VS Code with the extension
.py
and enter some simple Python code, e.g.:print("Testing Python install")
Click the ‘play’ button at the top of the open file.
Creating a team development repository¶
Log into GitHub (create an account using your @cam.ac.uk email address, or use any other GitHub account you wish).
One team member only: The template start code is at https://github.com/CambridgeEngineering/PartIA-Flood-Warning-System. Click on the green “Use this template” button, select “Create a new repository” give your new repository a name. Make your repository “private”. In the “Settings” section for your repository add your team members as “Collaborators” and share the name of the repository with team members.
Clone your team’s repository using VS Code “Source control”.
From VS Code, execute file
Task1A.py
. You should see some output on river level monitoring stations.
Note
The Python code uses some modules (requests
and dateutil
)
that are not part of the Python standard library. If you see an error
that a module is missing, you can install the module using pip
.
Use:
pip install requests python-dateutil
in the terminal window.
Editing and executing Python code¶
Launch VS Code and open your local code repository directory.
Open/create the files you wish to edit. ‘Module’ files should go in the directory
floodsystem/
. TheTask*.py
files should go in the root directory of the repository.Use right-click -> ‘Run Python File in Terminal’ on the program text in VS Code to run the Python code.
As you develop you programs, commit your changes (using Git) and push these to your shared online repository. If you are unsure how often to commit and push changes, err on the side of committing and pushing frequently. Commit at least upon the completion of each task.
Automated testing¶
The starter template repository includes the file
.github/workflows/pythonapp.yml
which configures automated testing,
known as continuous integration (CI), on GitHub. Against each commit
you will see on the GitHub repository page whether or not the tests are
passing.
Edit .github/workflows/pythonapp.yml
to run your deliverables in the
test system and to add code tests to your test suite.
Project planning¶
Examine the first few project deliverables, and divide independent tasks amongst team members. Each team member can then work on tasks independently.
Communicate frequently with team members to update them on your progress, and seek help from a team member if required.
As tasks are completed review each others work and provide feedback.
As you progress through the tasks, periodically assess which tasks are independent and allocate these to a team member.
Development tools and practices¶
Working in a team¶
Most software is developed in teams, and working effectively in a development team requires certain skills and practices. At a planning level:
Examine the required tasks, then discuss and decide on the dependencies between tasks. To start, allocate independent tasks to team members.
Let your team know when a task or piece of functionality is complete.
Discuss frequently.
At the implementation level:
Use a version control system, such as Git. With Git:
Work that is committed cannot be lost (unless you try really hard) - your team members cannot accidentally delete your code.
Commit changes frequently and in small chunks. This makes clear to others what you are working on, and any conflicts will be easier to resolve.
It is easy to switch between computers.
Add tests as functionality is developed. This:
Builds confidence that your implementation is correct.
Can detect if a change by you or a team member has affected your implementations. (One of the most frustrating situations in team development is when a change by another team members breaks your carefully constructed functionality.)
Using Git¶
Git is modern widely used version control system (VCS). A version control system tracks changes to source code. It can show what has changed, and who has made changes and when they made them. Git is very powerful and can be challenging to learn. Elementary Git usage for getting started is summarised below.
Git is generally used from the command line (terminal), but here are tools that provide graphical interfaces and some editors (e.g. VS Code) have built-in Git support.
VS Code¶
VS Code provides helpers for the operations in the following section.
Command-line use¶
Creating or cloning a repository¶
To clone a repository (typically hosted by an online service), e.g.:
git clone https://github.com/CambridgeEngineering/PartIA-Computing-Michaelmas.git
The location for a particular repository can be found on the online repository page.
To create a new repository, create a directory and execute in the directory the command:
git init
Adding a new file or adding file changes to the staging area¶
The command:
git add myfile.py
instructs Git that we want to track the file myfile.py
, or if the
file is already tracked that we will want to add any changes to the
repository history.
Committing changes to the project history¶
The commit
command commits changes to the project history, and each
commit has a ‘commit message’ associated with it:
git commit -m "Complete Task 1C"
It is possible at any time to see the changes between any two commits, and to revert a repository to a particular commit.
Collaborating: merging changes¶
To fetch remote changes into your repository, e.g. changes made by your team mate:
git pull
In general, you should commit
your changes before using pull
.
To send your changes to the remote server:
git push
If team members have ‘pushed’ changes, you will need to use git pull
before you can push. Once you have pushed changes, other team members
will receive your changes when they next ‘pull’.
Seeing changes in your working directory¶
The command:
git diff
shows any changes to your code since the last commit. The command:
git status
will show any changes to files that are (a) tracked but have changed
since the most recent commit, and (b) files that are not tracked (have
not been added using git add
).
Project history¶
The log of project commits is displayed by the command:
git log
The output will include the commit messages and the author of each commit.
Project history is shown by online services, like GitHub, and this the simplest way to examine project change. It is also possible to add comments and suggestions on particular code changes to discuss with team members.
How often should I commit changes?¶
Often. Structure your work into small chunks, and commit after completing each ‘chunk’. At the very least, you should commit changes at the completion of each Task in the Deliverables section.
Also, pull and push frequently.
Getting help with Git¶
There are many online resources for learning Git, and search engines for very useful. Helpful tutorials for beginners are:
Test framework¶
Testing is critical for high quality software development, and there are many tools for helping with this. In this project you will use pytest. Some tests are in the project starter repository.
Write tests as you go, and run the tests frequently to check that nothing has been inadvertently broken.
Running tests¶
pytest
is very simple to use:
Put tests in files starting with
test_
, e.g.test_data.py
.In the test file, prefix test function with
test_
, e.g.:def test_sum(): a, b = 2, 3 assert a + b == 5
To run all tests in all
test_*.py
files in a directory, use:pytest .
To run all tests in the file
test_data,py
:pytest test_data.py
pytest
will print a summary of the number of tests run, with the number that pass and the number that fail.
Writing tests¶
Aim to have at least one test for every function in your library. Some tests will just check that a function can be called successfully, e.g.:
import mymodule
def test_call():
x = mymodule.do_something(4)
More useful test will check results, e.g.:
import mymodule
def test_my_sum():
sum = mymodule.sum(7, -8)
assert sum == -1
Take care when comparing floating point values, since round-off errors can make precise comparison difficult. Use rounding to compare floats, e.g:
import math
def test_math_sine():
x = math.sin(0.0)
assert round(x, 8) == 0 # 'round' keep 8 digits after the decimal point
pi = 3.14159265359
x = math.sin(pi)
assert round(x, 8) == 0
pi = 3.14159265359
x = math.sin(pi/2.0)
assert round(x - 1, 8) == 0
Help and feedback¶
Get started early to give your team time to seek feedback and resolve issues. Issues/bugs are a feature of all software development and engineering.
There is a significant design component to this project. There is no one ‘best’ solution.
Help¶
Help channels for the activity are:
Peer support - this is encouraged, but be sure that you understand what you are doing.
Moodle forum.
Help Desk (see Moodle page for details).
Feedback¶
You can get feedback on your work from demonstrators at the Help Desk.
Suggestions for experienced developers¶
These development topics are optional, but are suggested for those who are already experienced with Git and Python and those who wish to develop their skills further.
Learning objectives and assessment¶
Learning objectives¶
Development skills
Approaches for working in teams.
Designing a working library for specific technical requirements.
Working to a realistic project specification.
Effective use of version control.
Devising tests.
Programming skills
Reinforcement of skills developed in Michaelmas Term.
Introduction to user modules and multi-file library implementations.
Working with user-defined objects.
Assessment guidelines¶
The following points will be used in assessing your implementation. Markers will want to view your Git log.
Code
Programs should execute without error.
Interfaces should conform to the specification in the Deliverables.
Programs should be correct.
Clarity and structure of the implementations.
Appropriate re-use of functions.
Documentation and process
Documentation of the library (both docstrings and comments in the code).
Unit tests.
Effective use of version control (commits of small steps with clear messages).
Balance of work within the team (as shown by the Git log).
Use of continuous integration.
Document license and copyright
These documents are licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. See http://creativecommons.org/licenses/by-sa/4.0/ for the license.
Copyright 2016-2024 by Garth N. Wells (gnw20@cam.ac.uk).
Documentation repository
These documents are managed at https://github.com/CambridgeEngineering/PartIA-Computing-Lent-doc.