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From: Stefan Monnier <monnier@IRO.UMontreal.CA>
To: Alan Mackenzie <acm@muc.de>
Cc: emacs-devel@gnu.org
Subject: Re: Thoughts on getting correct line numbers in the byte compiler's warning messages
Date: Wed, 07 Nov 2018 12:11:03 -0500	[thread overview]
Message-ID: <jwvh8gsyfy0.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <20181107123510.GA3966@ACM> (Alan Mackenzie's message of "Wed, 7 Nov 2018 12:35:10 +0000")

> Looking at notes I made at the time, I amended a small portion of e.g.
> byte-optimize-body to make a new hash entry with the same value when a
> form was transformed.  The slowdown on just the byte optimiser was
> around a factor of three.

Ouch!

> I don't think I follow myself here.  I was thinking that accessing a
> hash table element was slow, therefore keeping a table value current and
> pushing transformed forms onto it would be faster than creating a new
> hash table entry for these new forms.

Ah, so you'd keep a pointer to the list somehow and add to it by
side-effects.  Yes, I guess it would indeed be noticeably faster for the
case of copying the location info from the source code to the
transformed code.

> Looking at the code for hash tables, the access time can not be all
> that long.

Hash-table accesses are pretty costly, in my experience.


        Stefan



  reply	other threads:[~2018-11-07 17:11 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-01 17:59 Thoughts on getting correct line numbers in the byte compiler's warning messages Alan Mackenzie
2018-11-01 22:45 ` Stefan Monnier
2018-11-05 10:53   ` Alan Mackenzie
2018-11-05 15:57     ` Eli Zaretskii
2018-11-05 16:51       ` Alan Mackenzie
2018-11-06  4:34         ` Herring, Davis
2018-11-06  8:53           ` Alan Mackenzie
2018-11-06 13:56     ` Stefan Monnier
2018-11-06 15:11       ` Alan Mackenzie
2018-11-06 16:29         ` Stefan Monnier
2018-11-06 19:15           ` Alan Mackenzie
2018-11-06 20:04             ` Stefan Monnier
2018-11-07 12:35               ` Alan Mackenzie
2018-11-07 17:11                 ` Stefan Monnier [this message]
2018-11-07 17:00           ` Alan Mackenzie
2018-11-07 17:25             ` Stefan Monnier
2018-11-07 18:47               ` Alan Mackenzie
2018-11-07 19:12                 ` Stefan Monnier
2018-11-08 14:08                   ` Alan Mackenzie
2018-11-08 17:02                     ` Stefan Monnier
2018-11-08 22:13                       ` Alan Mackenzie
2018-11-11 12:59                         ` Alan Mackenzie
2018-11-11 15:53                           ` Eli Zaretskii
2018-11-11 20:12                             ` Alan Mackenzie
2018-11-11 20:47                               ` Stefan Monnier
2018-11-12  3:30                                 ` Eli Zaretskii
2018-11-12 16:19                               ` Eli Zaretskii
2018-11-12 14:16                             ` Alan Mackenzie
2018-11-12 15:44                     ` Alan Mackenzie
2018-11-12 20:36                       ` Stefan Monnier
2018-11-12 21:35                         ` Alan Mackenzie
2018-11-14 13:34                           ` Stefan Monnier
2018-11-15 16:32                             ` Alan Mackenzie
2018-11-15 18:01                               ` Stefan Monnier
2018-11-16 14:14                                 ` Alan Mackenzie
2018-11-08  4:47 ` Michael Heerdegen
2018-11-08 11:07   ` Alan Mackenzie
2018-11-09  2:06     ` Michael Heerdegen
2018-11-10 10:59       ` Alan Mackenzie
2018-11-10 13:20         ` Stefan Monnier
2018-11-11  7:56         ` Michael Heerdegen
2018-11-08 13:45   ` Stefan Monnier
2018-11-09  3:06     ` Michael Heerdegen
2018-11-09 16:15       ` Stefan Monnier

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