ELI5: Explain Like I'm 5

Alternating direction implicit method

Have you ever tried jumping rope with a friend or sibling? Remember how you both swung the rope in opposite directions to keep it going? That's kind of like what the Alternating Direction Implicit (ADI) method does – it takes turns going in two different directions to solve a complicated math problem.

In math, sometimes we have to solve equations that involve lots of different variables and are really hard to solve all at once. The ADI method breaks these equations down into smaller pieces that are easier to solve.

Here's how it works: let's pretend we have a math problem that looks like this:
5x + 3y = 20
6x - 2y = 10

First, we'd solve for x in the first equation by rearranging it:
5x = 20 - 3y
x = (20 - 3y)/5

Then we'd solve for y in the second equation:
-2y = 10 - 6x
y = (10 - 6x)/-2

Now we have a solution for both x and y, but they're not very accurate because we only used one equation at a time. This is where the ADI method comes in – instead of solving for x and y separately, it solves for them together by alternating between the x and y equations.

First, we'd use the x equation to find an approximate value for y. Then, we'd use that value of y in the y equation to find an approximate value for x. Then, we'd use that value of x in the x equation to find a more accurate value for y, and so on. We keep going back and forth between the equations until we get a pretty good solution for both x and y.

It's kind of like jumping rope – we take turns solving for x and y with each equation, just like how you and your friend take turns swinging the rope. And just like how you have to keep the rope going by swinging it in opposite directions, the ADI method keeps the solution going by alternating between the x and y equations.

And there you have it – the ADI method is like jumping rope with math equations!