* Re: [Emacs-diffs] feature/byte-switch c4316a2: ; bytecomp.el (byte-compile-cond-jump-table): Add TODO note
[not found] ` <20170206140315.229CD220145@vcs.savannah.gnu.org>
@ 2017-02-06 15:35 ` Stefan Monnier
2017-02-06 16:26 ` Clément Pit-Claudel
2017-02-06 16:57 ` Vibhav Pant
0 siblings, 2 replies; 6+ messages in thread
From: Stefan Monnier @ 2017-02-06 15:35 UTC (permalink / raw)
To: emacs-devel; +Cc: Vibhav Pant
> + ;; TODO: Once :linear-search is implemented for `make-hash-table'
> + ;; set it to `t' for cond forms with a small number of cases.
Indeed, we can probably substantially improve our hash-table performance
for small hash tables (not only in terms of CPU use but also in terms of
memory use).
But rather than a :linear-search keyword to make-hash-table, can't we
just test the value of `count` and use a linear search if it's small?
Stefan
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [Emacs-diffs] feature/byte-switch c4316a2: ; bytecomp.el (byte-compile-cond-jump-table): Add TODO note
2017-02-06 15:35 ` [Emacs-diffs] feature/byte-switch c4316a2: ; bytecomp.el (byte-compile-cond-jump-table): Add TODO note Stefan Monnier
@ 2017-02-06 16:26 ` Clément Pit-Claudel
2017-02-06 16:57 ` Vibhav Pant
1 sibling, 0 replies; 6+ messages in thread
From: Clément Pit-Claudel @ 2017-02-06 16:26 UTC (permalink / raw)
To: Stefan Monnier, emacs-devel; +Cc: Vibhav Pant
On 2017-02-06 10:35, Stefan Monnier wrote:
> Indeed, we can probably substantially improve our hash-table performance
> for small hash tables (not only in terms of CPU use but also in terms of
> memory use).
>
> But rather than a :linear-search keyword to make-hash-table, can't we
> just test the value of `count` and use a linear search if it's small?
This would be great. I currently have quite a bit of hash-table-heavy code with many relatively small hash tables, but in a few rare cases they can grow large, so alists don't cut it. A linear-search keyword wouldn't really help, because I can't tell beforehand which ones will be large.
Clément.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Emacs-diffs] feature/byte-switch c4316a2: ; bytecomp.el (byte-compile-cond-jump-table): Add TODO note
2017-02-06 15:35 ` [Emacs-diffs] feature/byte-switch c4316a2: ; bytecomp.el (byte-compile-cond-jump-table): Add TODO note Stefan Monnier
2017-02-06 16:26 ` Clément Pit-Claudel
@ 2017-02-06 16:57 ` Vibhav Pant
2017-02-06 17:27 ` Stefan Monnier
1 sibling, 1 reply; 6+ messages in thread
From: Vibhav Pant @ 2017-02-06 16:57 UTC (permalink / raw)
To: Stefan Monnier; +Cc: emacs-devel@gnu.org
On Mon, Feb 6, 2017 at 9:05 PM, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> But rather than a :linear-search keyword to make-hash-table, can't we
> just test the value of `count` and use a linear search if it's small?
Indeed. That should take less to code to implement too.
--
Vibhav Pant
vibhavp@gmail.com
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Emacs-diffs] feature/byte-switch c4316a2: ; bytecomp.el (byte-compile-cond-jump-table): Add TODO note
2017-02-06 16:57 ` Vibhav Pant
@ 2017-02-06 17:27 ` Stefan Monnier
2017-02-06 17:40 ` Stefan Monnier
0 siblings, 1 reply; 6+ messages in thread
From: Stefan Monnier @ 2017-02-06 17:27 UTC (permalink / raw)
To: emacs-devel@gnu.org
>> But rather than a :linear-search keyword to make-hash-table, can't we
>> just test the value of `count` and use a linear search if it's small?
Nitpick: actually, it should be based on the hash-table's *size* rather
than its *count*.
Stefan
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [Emacs-diffs] feature/byte-switch c4316a2: ; bytecomp.el (byte-compile-cond-jump-table): Add TODO note
2017-02-06 17:27 ` Stefan Monnier
@ 2017-02-06 17:40 ` Stefan Monnier
2017-02-06 18:22 ` Vibhav Pant
0 siblings, 1 reply; 6+ messages in thread
From: Stefan Monnier @ 2017-02-06 17:40 UTC (permalink / raw)
To: emacs-devel
>>> But rather than a :linear-search keyword to make-hash-table, can't we
>>> just test the value of `count` and use a linear search if it's small?
> Nitpick: actually, it should be based on the hash-table's *size* rather
> than its *count*.
For me, the place where small hash tables showed up is in cl-generic,
where many of them have just a single entry.
For byte-switch, optimizing the single-entry case is not important (you
wouldn't want to use byte-switch for it), tho.
Stefan
^ permalink raw reply [flat|nested] 6+ messages in thread
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[not found] ` <20170206140315.229CD220145@vcs.savannah.gnu.org>
2017-02-06 15:35 ` [Emacs-diffs] feature/byte-switch c4316a2: ; bytecomp.el (byte-compile-cond-jump-table): Add TODO note Stefan Monnier
2017-02-06 16:26 ` Clément Pit-Claudel
2017-02-06 16:57 ` Vibhav Pant
2017-02-06 17:27 ` Stefan Monnier
2017-02-06 17:40 ` Stefan Monnier
2017-02-06 18:22 ` Vibhav Pant
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