Deterministic floating point and .NET

I'm not sure of the exact answer for your question but you could use C++ and do all your float work in a c++ dll and then return the result to .Net through an interopt.

Bitexact results for different platforms are a pain in the a**. If you only use x86, it should not matter because the FPU does not change from 32 to 64bit. But the problem is that the transcendental functions may be more accurate on new processors.

The four base operations should not give different results, but your VM may optimize expressions and that may give different results. So as Ants proposed, write your add/mul/div/sub routines as unmanaged code to be on the safe side.

For the transcendental functions I am afraid you must use a lookup table to guarantee bit exactness. Calculate the result of e.g. 4096 values, store them as constants and if you need a value between them, interpolate. This does not give you great accuracy, but it will be bitexact.