# Exploring the Limitations of Floating Point Arithmetic and the Advantages of Number Theoretic Transform

Alessio Frateily

Feb 14, 20243 min read

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Exploring the Limitations of Floating Point Arithmetic and the Advantages of Number Theoretic Transform

### Introduction:

Floating point arithmetic plays a crucial role in computer hardware, representing numbers as binary fractions. However, due to the inherent nature of binary fractions, most decimal fractions cannot be precisely represented. On the other hand, the number theoretic transform offers an alternative approach, utilizing roots of unity modulo a specific number, which eliminates the need for floating point numbers. In this article, we will delve into the issues and limitations of floating point arithmetic while exploring the advantages of the number theoretic transform.

### Floating Point Arithmetic Limitations:

In floating point arithmetic, decimal fractions are approximated by binary fractions stored in the computer. For example, the decimal fraction 0.625 is represented as the binary fraction 0.101. While these two fractions have identical values, the real difference lies in their notations. This distinction becomes significant when precision is essential. The inability to precisely represent certain decimal fractions can lead to errors in calculations, especially in situations where accuracy is paramount.

Moreover, the representation of floating-point numbers in base 2 can result in unexpected outcomes. Subtle differences between decimal and binary fractions can lead to discrepancies and inaccuracies. These limitations highlight the need for alternative approaches that can overcome these challenges.

Number Theoretic Transform: A Solution for Modulo Arithmetic:

The number theoretic transform offers a solution to the limitations posed by floating point arithmetic. Similar to the fast Fourier transform (FFT), the number theoretic transform computes convolutions using roots of unity modulo a specific number, denoted as "μ." By operating within the realm of modulo arithmetic, the number theoretic transform eliminates the need for floating point numbers altogether.

Using roots of unity modulo μ allows for the representation of numbers within a finite field, resulting in precise calculations. This approach is particularly useful when dealing with computations that involve modular arithmetic, where precision and accuracy are crucial. By leveraging this alternative transform, the limitations of floating point arithmetic can be effectively circumvented.

Connecting Floating Point Arithmetic and Number Theoretic Transform:

Although floating point arithmetic and the number theoretic transform differ in their underlying principles, they share a common objective: accurately representing and manipulating numbers. While floating point arithmetic approximates decimal fractions, the number theoretic transform operates within a finite field, ensuring precise calculations through modulo arithmetic.

Considering the limitations of floating point arithmetic, it becomes evident that the number theoretic transform offers a promising alternative. By utilizing roots of unity modulo μ, this transform eliminates the inherent inaccuracies associated with floating point arithmetic.

• 1. Understand the limitations of floating point arithmetic: Recognize that decimal fractions cannot be precisely represented in binary fractions, which can lead to errors in calculations. Be mindful of situations where accuracy is crucial and consider alternative approaches if needed.
• 2. Explore the number theoretic transform: Familiarize yourself with the concept of roots of unity modulo μ and how they can be leveraged to perform precise calculations within a finite field. Identify scenarios where modular arithmetic is involved, as this is where the number theoretic transform shines.
• 3. Evaluate the applicability of alternative approaches: Assess whether the number theoretic transform aligns with your specific computational requirements. Consider the trade-offs and advantages it offers, such as increased precision, and determine if it is a suitable replacement for floating point arithmetic in your applications.

### Conclusion:

Floating point arithmetic has long been the go-to method for representing numbers in computer hardware. However, its limitations, such as the inability to precisely represent decimal fractions and the potential for inaccuracies, have prompted the exploration of alternative approaches. The number theoretic transform, with its roots of unity modulo μ, offers a viable solution for precise calculations within a finite field. By understanding the limitations of floating point arithmetic and exploring alternative approaches like the number theoretic transform, we can enhance the accuracy and reliability of numerical computations in various applications.

### Resource:

1. "15. Floating Point Arithmetic: Issues and Limitations", https://docs.python.org/3/tutorial/floatingpoint.html (Glasp)
2. "Number theoretic transform", https://wiki.algo.is/Number%20theoretic%20transform (Glasp)

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