But I am going to try to convince you why you should know about Chebyshev approximation, which is a technique for figuring out how you can come as clo

Chebyshev Approximation and How It Can Help You Save Money, Win Friends, and Influence People

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2024-06-08 01:00:06

But I am going to try to convince you why you should know about Chebyshev approximation, which is a technique for figuring out how you can come as close as possible to computing the result of a mathematical function, with a minimal amount of design effort and CPU power. Let's explore two use cases:

In Amy's case, she has a known function that seems difficult to compute. In Bill's case, he has an unknown function that he has to figure out how to model. These are both cases of function evaluation with two very different priorities. Both are on embedded systems, which brings me to the Central Hypothesis of Mathematical Computation on Embedded Systems (CHoMCoES? It needs a better name, and I don't feel like calling it the Sachs Hypothesis):

Let that sink in for a minute. Your computer is a wonderful thing. It can calculate pi to hundreds of decimal places in milliseconds, or model the airflow patterns around jet engine blades. The origins of the computer have been consistently centered around mathematical computation, with a huge surge of development around the end of the Second World War and through the early days of solid-state transistors. If you needed a computer in the 1940's and 1950's, it was for some precise mathematical calculation. Computers were very expensive to own and operate; if you needed a quick estimate of some math, there were slide rules. This was also the era where whole books were published containing tables of engineering functions, so that if you needed to calculate Bessel functions to 5 decimal places, you could do it by looking it up in a table.

The desktop computer uses a calculation strategy of "full machine precision": for a given bit representation, there is only one correct answer to sin(x), and it is the bit pattern that is the one yields the smallest error from the exact mathematical calculation. Someone has written and tested mathematical software libraries that do this, and from there on out, it's just a function call.