The other interesting trick is you need a separate RNG for visual only affects such as particles than the one you use for the physics simulation. Depending on the game during replays, you could position the camera differently and then particle effects would render differently depend, depending on what’s on screen. Obviously that shouldn’t affect the way objects decide to break during the physics simulation.
One of the hardest determinism bugs I had to solve on the PlayStation three was that the PPU and the SPU actually used a different instruction set and had a different internal floating point register size. We had a multi threaded physics simulation, and during instant replay, we had to ensure that the job scheduler sent the exact same work to the correct cores or we got back subtly different floating point values, which of course, immediately caused major divergences.
Instant replays that require long-term deterministic behavior have to be bit perfect in a way that is dramatically hard harder to implement if trying to also do network synchronization. The hard parts of each of those is fundamentally different and trying to do them at the same time terrifies me. I have shipped console games doing both (independently) and was responsible for de-bugging determinism.
Messaging platforms where people receive and promptly respond to messages are more successful in the long run. That's why SMS overtook email. If you own a messaging platform there isn't anything inherently nefarious about pushing people to enable notifications.
I was down there recently on a helicopter-based expedition and they set up a forward base of operations with a few days of emergency rations in case of unexpected weather that prevents you from returning to ship. I asked them what happens if the blizzard lasts more than a couple of days. Someone somewhere has a recipe book for penguins.
As best I can tell we've never sold the same product twice. Product roadmap is "whatever the last person I spoke to asked for." And tech debt maintaining a grab bag of 5,000 almost-but-not-quite-entirely-production-grade "must have" features that the customers rarely if ever use despite claiming that not having it was a deal breaker, is, well, debty.
> It is possible to create threads by using the OS syscalls bypassing completely the requirement of pthead. (Un)fortunately, I couldn’t find any popular libraries that implement the functionality by using the syscall interface instead of relying on pthread.
I have tried and failed to do this for a C++ program because the amount of C++ runtime static init/shutdown stuff you would need to deal with isn't practical to implement yourself.
CORE only works on kernels that support BTF. This post introduces one workaround which is to generate BTF data for kernels without it. That's still only half the problem though. You also need to write your eBPF program so every kernel verifier passes it, even though every kernel's eBPF verifier has different bugs, capabilities, and complexity limits. I maintain a large eBPF program that supports 4.14 through 6.14. We implemented our own version of CORE before CORE really existed. In reality, it's a lot more work than "compile once run everywhere."
As someone who studied physics and electronics for many years, I still appreciate an article like this for reminding me how profoundly weird science is. Working day to day with the equations and practical applications of electricity gives you a false sense of confidence that we actually have any fucking clue what’s going on.
GitHub pissed me off recently by giving us a one month reminder of our renewal, but having required two months notice to reduce our number of seats. As a result, we are ending up paying for twice as many seats as we currently need.
If you exceed the inheritance tax exemption then you are taxed on the $10k so LTCG would be double taxing. You could argue that the inheritance tax should have a much lower exemption but double taxation is harder to justify.
Listen. If it’s never supposed to happen then you definitely want a customer to tell you if it happens. Best way to make sure that happens is to insult their mum. It’s just good engineering discipline.
The physics game sim step had to be hardcoded but you could vary the graphics rendering independently. That did mean you needed to use a different RNG for sim objects and graphics-only particle effects.
I worked on the deterministic instant-replay system for a racing sim on PS3. The most interesting thing was that on PS3 we had main processor cores (PPU) and helper cores (SPU) which had their own instruction set. Our physics sim could distribute work across both, but the thread assignment had to be deterministic because PPU and SPU got marginally different floating point results for the same instructuion and inputs. That was a fun one to figure out!