The linear search code has been shifted to bytecode.c, since there are a
couple of assumptions about the jump table that we can't make for a regular
hash table, so regular gethash shouldn't be affected.

Vibhav Pant
vibhavp@gmail.com

On 10-Feb-2017 12:45 AM, "Clément Pit-Claudel" <cpitclaudel@gmail.com>
wrote:

> On 2017-02-08 08:38, Vibhav Pant wrote:
> > On Tue, Feb 7, 2017 at 9:26 PM, Clément Pit-Claudel
> > <cpitclaudel@gmail.com> wrote:
> >> The timings fluctuate quite a bit, but the byte-switch branch seems to
> be about 5-7% slower.  Hopefully linear-scan hash tables will make things
> much faster :)
> >
> > The following patch makes hash_lookup use linear search when the number
> of keys
> > in the hash table is <= 5 (chosen arbitrarily). switch bytecode run with
> this
> > patch takes 15.96 seconds to run the benchmark, while the goto-if-nil
> code takes
> > 17.15 seconds.
>
> Here's another test that your patch seems to improve a bit:
>
> (defvar ~/maps nil)
>
> (dotimes (n 50)
>   (let ((map (make-hash-table :test #'eq)))
>     (dotimes (k 2)
>       (puthash k n map))
>     (push map ~/maps)))
>
> (benchmark-run-compiled 1000000
>   (dolist (mp ~/maps)
>     (gethash 1 mp)))
>
> Are linear scans used on all small hash tables, then?
>
> Clément.
>
>