bert at freudenbergs.de
Sat Jan 10 14:27:10 UTC 2009
On 10.01.2009, at 11:01, Josh Gargus wrote:
> As noted by John, Croquet uses fdlibm for bit-identical floating
> point math. Does anyone have a feeling for how difficult (or
> impossible) it will be to achieve identical computation on OpenCL-
> compliant devices?
The numerical behavior of compliant OpenCL implementations is covered
in section 7 of the OpenCL spec. In particular, table 7.1 gives the
error bounds for the various operations. If I interpret that
correctly, very few functions are guaranteed to behave bit-identical.
> For example, how difficult would it be to port, say, fdlibm, so
> that trancedentals use the exact same code? Any other show-stoppers
> that might not occur to the naive mind :-) ?
Well OpenCL only requires single-precision, double-precision support
is optional, whereas fdlibm is double-precision only. I don't know how
compliant current implementations actually are.
- Bert -
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