On Wednesday, 18 May 2016 at 11:17:14 UTC, Walter Bright wrote:
Again, even if the precision matches, the rounding will NOT match, and you will get different results randomly dependent on the exact operand values.
We've already been burned by middlewares/APIS toggling MMX flags on and off and not cleaning up after themselves, and as such we strictly control those flags going in to and out of such areas. We even have a little class with implementations for x87 (thoroughly deprecated) and SSE that is used in a RAII manner, copying the MMX flag on construction and restoring it on destruction.
I appreciate that it sounds like I'm starting to stretch to hold to my point, but I imagine we'd also be able to control such things with the compiler - or at least know what flags it uses so that we can ensure consistent behaviour between compilation and runtime.
