Cross Platform Floating Point Consistency

Question

I\'m developing a cross-platform game which plays over a network using a lockstep model. As a brief overview, this means that only inputs are communicated, and all game log

Answer 1

1.) In principle cross platform, OS, hardware compatibility is possible but in practice it's a pain.

In general your results will depend on which OS you use, which compiler, and which hardware you use. Change any one of those and your results might change. You have to test all changes. I use Qt Creator and qmake (cmake is probably better but qmake works for me) and test my code in MSVC on Windows, GCC on Linux, and MinGW-w64 on Windows. I test both 32-bit and 64-bit. This has to be done whenever code changes.

2.) and 3.) In terms of floating point some compilers will use x87 instead of SSE in 32-bit mode. See this as an example of the consequences of when that happens Why a number crunching program starts running much slower when diverges into NaNs? All 64-bit systems have SSE so I think most use SSE/AVX in 64-bit otherwise, e.g. in 32 bit mode, you might need to force SSE with something like -mfpmath=sse and -msse2.

But if you want a more compatible version of GCC on windows then I would used MingGW-w64 for 32-bit (aka MinGW-w32) or MinGW-w64 in 64bit . This is not the same thing as MinGW (aka mingw32). The projects have diverged. MinGW depends on MSVCRT (the MSVC C runtime library) and MinGW-w64 does not. The Qt project has a pretty good description of MinGW-w64 and installiation. http://qt-project.org/wiki/MinGW-64-bit

You might also want to consider writing a CPU dispatcher cpu dispatcher for visual studio for AVX and SSE.