English: This image is an update of File:Double pendulum flip time 2021.png with a few changes and fixes:

• The color scheme now uses discrete color ranges as opposed to being continuous, which better aligns with how it's described in the Wikipedia article (red for 1–10, green for 10–100 etc.). The image now consists of only four distinct color hues + black and white.
• The previous version has some artifacts (e.g. white pixels scattered along the edges of the image, colored pixels in areas that should be all white, occasional color banding) that are fixed here.
• The resolution is much higher, and is oversampled from an even higher resolution.

Now to the actual description:

The colors in the graph represent the time it takes a compound double pendulum with bars of equal mass and length to flip based on the initial angles of the bars. The horizontal axis represents the first pendulum, and the vertical axis represents the second pendulum. The graph goes from ${\displaystyle -\pi }$ to ${\displaystyle \pi }$ in both directions. Time units are in ${\displaystyle {\sqrt {l/g}}}$; colors are assigned to pixels based on how quickly either pendulum flips:

• < 1: black
• 1–10: red (light red to dark red)
• 10–100: green (light green to dark green)
• 100–1000: blue (light blue to dark blue)
• 1000–10000: purple (light purple to dark purple)
• No flip observed within 10000 time units: white

The calculation was done using an 8th order Runge-Kutta method with a time step of 0.02 using 32-bit floating point. The resulting 12000×12000 image was oversampled from an impractically large 48000×48000 image, which took 5 hours to generate on a GPU.