Factorio Forums

• Technology researched message does not play chat notification sound.

• Fixed that the prototype explorer and CustomInputEvent::selected_prototype did not work on crafting machine fluid slots.
• Fixed LuaEntity::disconnect_neighbour called on electric pole would disconnect left side of power switch when requested to disconnect right side. (109309)
• Fixed that cloning rails in the map editor could lead to corrupt saves in some instances. (109436)
• Fixed offset of circuit connector sprites for inserters

• Added PrintSettings::sound_path, volume_modifier and game_state.
• Replaced PrintSettings::skip_if_redundant with PrintSettings::skip. Added defines.print_skip.

Rseding91 wrote: ↑

Tue Nov 07, 2023 3:29 pm

This experimental version also contains cross-platform checks for x86 vs arm floating point conversions. x86 and arm do floating point conversions differently and if we don't handle it correctly on the C++ side it results in different values which results in multiplayer desyncs.

AugustoResende wrote: ↑

Wed Nov 08, 2023 9:55 pm

If you play in a Linux machine (x86) and your friend is playing in a M1 Mac Os, without this fix in some cases could occur a multiplayer desync because of different fload calculations

Stringweasel wrote: ↑

Wed Nov 08, 2023 1:34 pm

As a programmer myself I'm curious what exactly you mean here. I understand the part that different platforms do floating point operations differently, and they might have different results. And because Factorio is deterministic it's very important that all calculations always result in exactly the same answer.

But isn't this something that should be checked during development? Or in CI/CD pipelines? My first guess is that there's simply too many things to check?

And what type of checks was added? For example, the Factorio instance on my PC will do a floating point calculation, but to what would the result be compared (checked) to verify it's consistent?

Genhis wrote: ↑

Thu Nov 09, 2023 1:22 pm

Stringweasel wrote: ↑

Wed Nov 08, 2023 1:34 pm

As a programmer myself I'm curious what exactly you mean here. I understand the part that different platforms do floating point operations differently, and they might have different results. And because Factorio is deterministic it's very important that all calculations always result in exactly the same answer.

But isn't this something that should be checked during development? Or in CI/CD pipelines? My first guess is that there's simply too many things to check?

And what type of checks was added? For example, the Factorio instance on my PC will do a floating point calculation, but to what would the result be compared (checked) to verify it's consistent?

Floating-point operations still have to do the same thing, otherwise cross-architecture multiplayer wouldn't work at all. This release added checks for conversion from floating-point numbers to integers. One of the issues we encountered was converting `double(-1)` into `uint32_t` - x86 lets it overflow and arm clamps it to 0 (105953). So it's mostly about checking if a floating-point value is in range of the target type and clamping it if it doesn't fit.

We do compare CRC values of our tests between x86 and arm, but sometimes we make incorrect assumptions or don't think about stuff modders would do. (Who would define a technology cost larger than ~18 quintillion, right? ) Also, not every line of code can be reliably tested. Runtime checks help us to fill in these gaps.