Re: [PATCH] Re: Bignum performance (was: Shrinking the C core)

[Emanuel Berg]

Ihor Radchenko wrote:

> The main problem your benchmark demonstrated is with bignum.
> By accident, it also revealed slight inefficiency in vector
> allocation, but this inefficiency is nowhere near SBCL 0.007
> sec vs. Elisp 2.5 sec.

Yeah, we can't have that.

> In practice, as more generic benchmarks demonstrated, we
> only had 10% performance hit. Not something to claim that
> Elisp is much slower compared to CL.

What do you mean, generic +10% is a huge improvement.

> It would be more useful to compare CL with Elisp using less
> specialized benchmarks that do not involve bignums.
> As Mattias commented, we do not care much about bignum
> performance in Elisp - it is a rarely used feature; we are
> content that it simply works, even if not fast, and the core
> contributors (at least, Mattias) are not seeing improving
> bignums as their priority.

But didn't your patch do that already?

It would indicate that it is possible to do it all in/to
Elisp, which would be the best way to solve this problem _and_
not have any of the integration, maybe portability issues
described ...

So 1, the first explanation why CL is much faster is another
implementation of bignums handling which is faster in CL, if
that has already been solved here absolutely no reason not to
include it as 10% is a huge gain, even more so for a whole set
of benchmarks.

Instead of relying on a single benchmark, one should have
a set of benchmarks and every benchmark should have a purpose,
this doesn't have to be so involved tho, for example "bignums"
could be the purpose of my benchmark, so one would have
several, say a dozen, each with the purpose of slowing the
computer down with respect to some aspect or known
situation that one would try to provoke ... It can be
well-known algorithms for that matter.

One would then do the same thing in CL and see, where do CL
perform much better? The next question would be, why?

If it is just about piling up +10%, let's do it!

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