On Thursday, 17 December 2015 at 11:50:02 UTC, drug wrote:
I have two implementation of the same algorithm - D and C++ (that is port of D version). I assume that running these implementations on the same data should give the same results from both. But with some data the results differ (5th decimal digit after point). For my purpose it isn't important and I can ignore this difference. But I'd like to have the same results totally (I mean bit to bit) to easy maintanence of the implementations. Question is - can I rely that D and C++ float types operations should give the same result because D and C are similar or no and I should use more portable way and compare floats with some epsilon?
If you aim for float reproducibility, you will get trouble in 32-bit vs 64-bit mode, depending on whether the FPU is used or not. The FPU promotes to 80-bits code that uses float or double, and may get you more precision thus changing the results.
