On: Ask HN: How do you debug your code?

[dfan]

Yes, exactly. Assuming that the error was not in the rendering system, which took the bulk of the CPU time and which was isolated as much as possible, the recording could even be replayed at high speed by omitting the rendering of most frames.

I forgot to mention that we actually found a lot of bugs by seeing a playback diverge from the original recording; this was often due to uninitialized variables or reading from random memory. We could generally see when the divergence happened because we computed a checksum of the state of the world every frame and stored it in the recording as well.

[blub → dfan]

Interesting stuff, games seem like an ideal target for such recording, because their data is available offline and they are by nature event-focused.

I wonder how/if this could be applied to network-facing software like a daemon, or programs that transform large amounts of data.