On 20 Jun 00, at 14:41, Griffith, Shaun wrote:
>
> One drawback is the possibility of comparing apples to oranges, i.e., one
> combination running with a different system loading than another.
If the self-tuning is being done on the same system that's running
the bulk of the work (which I think is the idea), this shouldn't be a
problem. A real, practical problem related to this is that varying
system load may make a significant difference as to the relative
efficiency of two methods, so you'd have to be careful about how you
did the timing.
e.g. on Intel processors, whether or not MMX is in use by another
active process substantially affects the performance of anything
which thrashes the FPU, because the MMX & FPU register sets are
common & switching between MMX mode & FPU mode is relaitively slow.
> Another drawback is of course is to manage the added memory taken up
> "redundant" code. However, with the exponents running now the code size
> should be negligible compared to the data.
On IA32 systems, how the code is aligned is also a factor. To compare
accurately, you'd really need the seperate code fragments to be in
their own dedicated segments. This is not the way that un*x or Win32
applications are usually coded.
Another problem suggests itself - this code would take a lot more
debugging, for reasons which ought to be self-evident. Also, you'd
need to label each result with the method used.
Regards
Brian Beesley
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