Algorithm
In short
An algorithm is a set of step-by-step instructions for reaching a result, like a recipe a computer can follow. In AI, algorithms are used both to train models on data and to make automated decisions about people.
- Also called
- Algorithms
- Topic
- The basics
- Level
- Beginner
- First described
- The word comes from the name of the Persian author al-Khwarizmi, whose book of arithmetic rules dates from about 825 AD, according to NIST's Dictionary of Algorithms and Data Structures1.
The US standards body NIST defines an algorithm as "a computable set of steps to achieve a desired result"1. Sorting a list, finding a route and calculating a loan repayment are all done by algorithms.
In AI the word often means the training method. Backpropagation, for example, is the algorithm that tells a neural network how to change its internal parameters2. The trained result is usually called a model, though everyday speech blurs the two. The ICO describes AI as "an umbrella term for a range of algorithm-based technologies"3.
An algorithm does not need to involve AI to affect lives. In summer 2020, with exams cancelled because of COVID-19, Ofqual used a statistical standardisation process to award A level grades in England4. Schools submitted grades and a rank order for each subject, and predictions used the relationship between students' prior attainment and past results4.
On 17 August 2020 the government and Ofqual reversed course. They said "the algorithm has revealed a number of anomalies" that "severely undermined confidence in the system", and switched to teacher-assessed grades5.
Example
A satnav working out your quickest route home is running an algorithm: a fixed series of steps that compares possible roads and picks the one with the shortest expected journey time.
Why it matters
Algorithms increasingly make or shape decisions about people, from exam grades to credit, so it matters who wrote the steps and what data they use5.
Questions people ask
Is an algorithm the same as AI?
No. An algorithm is any computable set of steps to reach a result1. AI systems are built with algorithms, but most algorithms, such as a spreadsheet formula, involve no AI at all.
What was the A level algorithm?
In 2020 Ofqual used a statistical standardisation process to award grades in England, based on teachers' rank orders and predictions from prior attainment4. On 17 August 2020 it was dropped for teacher-assessed grades after producing anomalies5.
Where does the word algorithm come from?
From the name of al-Khwarizmi, a Persian author whose book of arithmetic rules dates from about 825 AD1.
Related terms
Sources
- Black, P. E. (ed.), NIST Dictionary of Algorithms and Data Structures, "algorithm"
- LeCun, Bengio and Hinton (2015), Deep learning, Nature 521, 436-444
- ICO, Explaining decisions made with AI, Part 1: Definitions
- Ofqual (13 August 2020), Guide to AS and A level results for England, 2020
- Department for Education (17 August 2020), GCSE and A level students to receive centre assessment grades