mirror of
https://github.com/catchorg/Catch2.git
synced 2024-11-21 21:06:11 +01:00
Mention x87 and ffast-math breaking FP random gen reproducibility
This commit is contained in:
parent
2e1b02a0e2
commit
28c2f0b0c2
@ -206,12 +206,26 @@ or OO ranges.
|
||||
Unlike `std::uniform_int_distribution`, Catch2's generators also support
|
||||
various single-byte integral types, such as `char` or `bool`.
|
||||
|
||||
Given the same seed, the output from the integral generators is
|
||||
reproducible across different platforms. For floating point generators,
|
||||
we only promise reproducibility on platforms that obey the IEEE 754
|
||||
standard, and where `float` is 4 bytes and `double` is 8 bytes. We provide
|
||||
no guarantees for `long double`, as the internals of `long double` can
|
||||
vary wildly across different platforms.
|
||||
|
||||
#### Reproducibility
|
||||
|
||||
Given the same seed, the output from the integral generators is fully
|
||||
reproducible across different platforms.
|
||||
|
||||
For floating point generators, the situation is much more complex.
|
||||
Generally Catch2 only promises reproducibility (or even just correctness!)
|
||||
on platforms that obey the IEEE-754 standard. Furthermore, reproducibility
|
||||
only applies between binaries that perform floating point math in the
|
||||
same way, e.g. if you compile a binary targetting the x87 FPU and another
|
||||
one targetting SSE2 for floating point math, their results will vary.
|
||||
Similarly, binaries compiled with compiler flags that relax the IEEE-754
|
||||
adherence, e.g. `-ffast-math`, might provide different results than those
|
||||
compiled for strict IEEE-754 adherence.
|
||||
|
||||
Finally, we provide zero guarantees on the reproducibility of generating
|
||||
`long double`s, as the internals of `long double` varies across different
|
||||
platforms.
|
||||
|
||||
|
||||
|
||||
## Generator interface
|
||||
|
Loading…
Reference in New Issue
Block a user