ELI5: Explain Like I'm 5

Schwarz alternating method

The Schwarz alternating method is a way of solving a problem by breaking it down into smaller parts and then solving each part one at a time.

Imagine you have a big jigsaw puzzle with many pieces. Instead of trying to assemble all the pieces at once, you could separate the puzzle into smaller sections and assemble each section one at a time. The Schwarz alternating method works in a similar way.

Let's suppose we have a problem that we want to solve, but it is too big to solve all at once. We can divide the problem into smaller parts, called subdomains. Each subdomain is like a smaller puzzle piece that we can solve more easily than the whole problem.

However, there is a catch. These subdomains are not completely independent of each other, meaning that the solution in one subdomain can affect the solution in another subdomain. In terms of our puzzle analogy, imagine that the pieces share borders or edges, so we have to make sure the pieces fit together properly.

To make sure the subdomains fit together, we use a process called the Schwarz alternating method. This method involves solving each subdomain separately, but also considering the solution in the neighboring subdomains and updating our solution accordingly.

Here's how it works:

First, we start by making an initial guess for the solution of the entire problem. Then, we divide the problem into subdomains and solve each subdomain individually, ignoring its interaction with the other subdomains.

Next, we update the solution in each subdomain by considering the solutions in the neighboring subdomains. We do this by adding a correction term to the subdomain solution. The correction term accounts for any inconsistencies between neighboring subdomains.

After we have updated the solutions for all subdomains, we repeat this process by solving each subdomain again and updating the solutions based on the neighboring subdomains. We continue to repeat this process until the solution for the entire problem is accurate enough.

In summary, the Schwarz alternating method is a way to solve a big, complicated problem by breaking it down into smaller, more manageable parts. We solve each part separately but also consider the interactions between neighboring subdomains to ensure a final solution that fits together properly.