Question

I am looking at writing an application which calculates temperatures spread in a material with an exposure (such as fire) over time.

I then need to draw the result as a heat map on the geometry of the material.

Now I wonder if I should in general go with Decimal or Double for all calculations and drawing. I have looked into both but are still unsure which to use.

I will need to compare values, including interpolated values over time. And double have as far as I understand it comparison problems due to inexact representation.
But decimal is heavy to work with.

I am leaning towards double only but at the same time more exact representation and comparison is worth a lot too.

Answer 1

Any finite representation of decimal numbers is bound to have the same “inexact representation” issues as a finite binary representation. Not all real numbers can be represented in finite space and going to base 10 is not going to help there.

Decimal just uses the same bits less efficiently—when talking of representing a physical simulation. On the other hand, a particular implementation of decimal numbers may allow to use more bits, but multi-precision binary floating-point implementations are available too.

The superstition that decimal floating-point libraries would somehow not be “inexact” or have “comparison problems” is widespread because these libraries can represent exactly decimal numbers, starting with 0.1. If your simulation involves coefficients that are powers of ten, then decimal would indeed be a good fit. Otherwise, decimal will not solve any of the problems inherent to the finite representation of a continuous range of numbers.