22.07.2019 17:19, drug пишет:
22.07.2019 16:26, Guillaume Piolat пишет:
Typical floating point operations in single-precision like a simple
(a * b) + c will provide a -140dB difference if order is changed.
It's likely the order of operations is not the same in your program,
so the least significant digit should be different.
What I would recommend is compute the mean relative error, in double,
and if it's below -200 dB, not bother. This is an incredibly low
relative error of 0.00000001%.
You will have no difficulty making your D program deterministic, but
knowing exactly where the C++ and D differ will be long and serve no
purpose.
Unfortunately error has been turned out to be much bigger than I guessed
before. So obviously there is a problem either on D side or on C++ side.
Error is too huge to ignore it.
There was a typo in C++ implementation. I did simple-n-dirt Python
version and after the typo fixed all three implementations show the same
result if one filter update occurs. But if several updates happen a
subtle difference exists nevertheless, error accumulates somewhere else
- time for numerical methods using.
