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# What is approximation error?

by Stephen M. Walker II, Co-Founder / CEO

## What is approximation error?

Approximation error refers to the difference between an approximate value or solution and its exact counterpart. In mathematical and computational contexts, this often arises when we use an estimate or an algorithm to find a numerical solution instead of an analytical one. The accuracy of the approximation depends on factors like the complexity of the problem at hand, the quality of the method used, and the presence of any inherent limitations or constraints in the chosen approach.

For instance, consider the task of finding the square root of a number using Newton's method. While this technique provides an increasingly accurate estimate as you iterate through the process, there will always be some level of error between the computed value and the actual square root due to its iterative nature. Similarly, when solving differential equations numerically, there is inherent approximation error introduced by discretizing the continuous domain into discrete points or steps.

In practice, understanding and managing approximation errors are crucial for developing reliable algorithms and ensuring that their outputs are within an acceptable tolerance of the true values. Strategies to minimize approximation errors may include refining methods, adjusting parameters, or using more advanced techniques that can provide better approximations with fewer iterations or computational resources.

## What causes approximation error?

Approximation error is primarily caused by two factors: the inherent limitations of the chosen method and the level of detail or accuracy required for the given problem.

1. Inherent limitations of the chosen method: Some methods used to approximate values or solve problems may have inherent inaccuracies built into them due to their design or underlying assumptions. For example, numerical integration techniques like the trapezoidal rule and Simpson's rule are known to have certain errors associated with them, which depend on factors such as the step size and degree of polynomial used for approximation.

2. Level of detail or accuracy required: The extent of the approximation error can be influenced by how much detail is needed in the final result. If a high degree of precision is required, then methods that provide coarse approximations may lead to larger errors. Additionally, constraints on computational resources and time can force developers to choose faster but less accurate algorithms over more accurate ones that would require significantly more processing power or time to complete.

To minimize approximation error, it is essential to carefully select an appropriate method for the problem at hand and to balance the trade-off between accuracy and efficiency. This may involve iteratively refining the chosen approach, adjusting its parameters, or employing more advanced techniques that can provide better approximations with fewer iterations or computational resources.

## How can approximation error be reduced?

Reducing approximation error in mathematical and computational contexts involves a combination of strategies. The first step is to select an appropriate method for the problem at hand, considering its inherent accuracy and limitations. For example, when numerically solving differential equations, techniques like adaptive quadrature or spectral methods may offer better approximations than simpler methods like the trapezoidal rule or Simpson's rule.

Once a method is chosen, its parameters can be fine-tuned to improve accuracy. For instance, in Newton's method for finding square roots, smaller initial guesses and a larger number of iterations can yield more accurate results. Similarly, in numerical integration techniques, an optimal step size or degree of polynomial approximation can help reduce errors.

If the chosen method can be iteratively improved, multiple iterations can be performed and their results combined, such as through averaging, to obtain a more accurate estimate. This is often used in scenarios like numerical integration, where successive refinements of the step size or degree of polynomial approximation can lead to progressively smaller errors.

Understanding the convergence properties of the chosen method can also be beneficial. This analysis can inform decisions about when to stop iterating and accept a computed result, or whether it might be beneficial to switch to a more advanced technique that offers faster convergence or better overall accuracy.

Finally, estimating the expected error in the computed result based on the chosen method, its parameters, and any inherent limitations or constraints can be useful. An appropriate tolerance for this estimated error can then be set, beyond which the computed result is deemed insufficiently accurate and should be further refined or recomputed with a different approach.

By integrating these strategies, developers can minimize approximation errors in their algorithms, ensuring their outputs maintain acceptable levels of accuracy and precision for the given problem.

## What are the consequences of approximation error?

Approximation error, if not properly managed, can lead to several adverse consequences. Firstly, it can result in inaccurate or unreliable results, which is particularly problematic in fields like finance, engineering, and science where even minor errors can significantly impact decision-making and outcomes. Secondly, as the approximation error increases, so does the need for computational resources and iterations to achieve the desired level of accuracy.

This not only leads to higher resource consumption, such as processing power, memory, and time, but also reduces the efficiency of algorithms and systems, especially in real-time or resource-constrained environments. Thirdly, approximation errors can lead to poor decision-making or flawed conclusions as users may base their choices on incorrect information or overly simplified models.

Lastly, as methods for reducing approximation error become more advanced, developers may need to invest additional time and effort into understanding, implementing, and maintaining these techniques, increasing overall development and maintenance costs.

Therefore, it is crucial for developers to carefully select appropriate methods, fine-tune parameters as needed, and employ strategies like iterative refinement or error estimation to minimize errors and ensure computed results are accurate and reliable within acceptable tolerance levels.

## How does approximation error impact the AI field?

Approximation error significantly impacts various aspects of artificial intelligence (AI). During machine learning model training, techniques such as stochastic gradient descent or mini-batch optimization methods inherently introduce approximation errors. These errors can affect the speed of convergence and the accuracy of the models, impacting their performance on real-world tasks and datasets.

The architecture of neural networks, including layer depth and the number of neurons per layer, directly influences the approximation error in deep learning applications. Simplified or shallow networks may have larger errors due to their limited capacity to capture complex patterns and relationships in the input data.

Many AI systems depend on optimization techniques to find optimal solutions. These include reinforcement learning agents navigating environments and evolutionary algorithms evolving populations of candidate solutions. Approximation errors in these optimization methods can lead to suboptimal or inefficient outcomes, affecting the performance and effectiveness of the AI applications.

In robotics and control systems, approximation errors can occur from models used to simulate and predict the behavior of physical systems, such as dynamic models of mechanical components, fluid flow, or chemical reactions. These errors can impact the accuracy and robustness of control strategies or decision-making algorithms that rely on these models for planning and execution in real-world scenarios.

In many AI applications, raw sensor data is processed and transformed into meaningful information through techniques like filtering, feature extraction, or classification. Approximation errors introduced during this preprocessing stage can impact the quality and reliability of the output, affecting downstream tasks like decision-making or action planning in real-time environments.

To mitigate approximation errors in AI applications, researchers and developers can select appropriate model architectures, tune optimization algorithms, analyze convergence properties, estimate error bounds, and incorporate error mitigation techniques into their system designs. This ensures that computed results are accurate and reliable within acceptable tolerance levels.

## More terms

### What is the anytime algorithm?

The anytime algorithm is a type of algorithm that continually improves its output or solution over time, even if it does not have a specific stopping condition. These algorithms can be useful in situations where the optimal solution may take a long time to compute or when there is a need for real-time decision-making.

### What is a restricted Boltzmann machine?

A restricted Boltzmann machine is a type of artificial intelligence that can learn to represent data in ways that are similar to how humans do it. It is a neural network that consists of two layers of interconnected nodes. The first layer is called the visible layer, and the second layer is called the hidden layer. The nodes in the visible layer are connected to the nodes in the hidden layer, but the nodes in the hidden layer are not connected to each other.