On Tue, May 5, 2009 at 8:06 PM, Jean-Marc Eber <jeanmarc.eber@lexifi.com> wrote:
> Hi Dimitry,
>
> Firstly thanks for looking again at the sse2 stuff!
>
> A difference may occur, if I'm not wrong, from the intermediate results
> precision:
>
> in sse2, eveything is done on 8 bytes (if you "do" doubles at least), while,
> in x87, intermdiate results (kept on the stack) are 10 bytes precision.
>
> This may result in differences (and the bytecode runtime never uses x87
> intermediate storage, so it behaves _numerically_ like the sse2 code
> generator, I guess).

I wouldn't be so sure. Bytecode runtime is C compiler-dependent (that
does use x87 for floating-point calculations), so rounding errors can
lead to different results. Floating point is always approximate...

- Dmitry Bely