Re: Algorithm Optimization

Path	csiph.com!news.uzoreto.com!tr2.eu1.usenetexpress.com!feeder.usenetexpress.com!tr2.iad1.usenetexpress.com!border1.nntp.dca1.giganews.com!nntp.giganews.com!news.iecc.com!.POSTED.news.iecc.com!nerds-end
From	"Derek M. Jones" <derek@_NOSPAM_knosof.co.uk>
Newsgroups	comp.compilers
Subject	Re: Algorithm Optimization
Date	Wed, 16 Sep 2020 20:11:04 +0100
Organization	virginmedia.com
Lines	43
Sender	news@iecc.com
Approved	comp.compilers@iecc.com
Message-ID	<20-09-039@comp.compilers> (permalink)
References	<20-09-032@comp.compilers> <20-09-035@comp.compilers> <20-09-036@comp.compilers>
Mime-Version	1.0
Content-Type	text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding	8bit
Injection-Info	gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="77785"; mail-complaints-to="abuse@iecc.com"
Keywords	optimize, performance
Posted-Date	16 Sep 2020 17:34:22 EDT
X-submission-address	compilers@iecc.com
X-moderator-address	compilers-request@iecc.com
X-FAQ-and-archives	http://compilers.iecc.com
In-Reply-To	<20-09-036@comp.compilers>
Content-Language	en-US
Xref	csiph.com comp.compilers:2610

Show key headers only | View raw

On 16/09/2020 06:25, gah4 wrote:

> Now, say someone is doing their CS project for class, where they are
> supposed to write, and time, bubblesort?

I don't think student projects should be a factor in implementation of
industrial compilers.

> I suppose you can find a Chebyshev series that closely approximates
> the series coded, but takes fewer terms.
>
> But what about the person who wants to compare two series'?
> If you replace one or both, then the comparison will be wrong.

More edge cases.

I'm sure you know about Herbie: https://herbie.uwplse.org/

> Not that there haven't been problems since the beginning of
> optimizing compilers, where the results were different than
> expected.

There probably won't be too many places where savings can be made.
The compiler could highlight them.

There are always people willing to pay for faster code, and there will
be compiler writers willing to implement go faster stuff.

> [Back when people cared about Whetstone and Dyrystone benchmarks,
> compilers recognized code sequences from those benchmarks for, uh,
> special processing.  But it doesn't generalize very well. -John]

Intel and ??? have both been caught doing this.  See chapter 13 oof
this book: http://www.knosof.co.uk/ESEUR

Benchmarking these days has gotten to be very unreliable:
https://shape-of-code.coding-guidelines.com/2015/02/24/hardware-variability-may-be-greater-than-algorithmic-improvement/

http://shape-of-code.coding-guidelines.com/2020/01/05/performance-variation-in-2386-identical-processors/

--
Derek M. Jones
blog:shape-of-code.coding-guidelines.com

Back to comp.compilers | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

Algorithm Optimization "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2020-09-13 13:00 -0400
  Re: Algorithm Optimization Elijah Stone <elronnd@elronnd.net> - 2020-09-14 20:47 -0700
    Re: Algorithm Optimization "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2020-09-15 00:42 -0400
  Re: Algorithm Optimization "Derek M. Jones" <derek@_NOSPAM_knosof.co.uk> - 2020-09-15 14:29 +0100
    Re: Algorithm Optimization gah4 <gah4@u.washington.edu> - 2020-09-15 22:25 -0700
      Re: Algorithm Optimization "Derek M. Jones" <derek@_NOSPAM_knosof.co.uk> - 2020-09-16 20:11 +0100
      Re: Algorithm Optimization Richard Harnden <richard.nospam@gmail.com> - 2020-09-16 22:45 +0100
      Re: Algorithm Optimization Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2020-09-17 06:35 +0200
        Re: Algorithm Optimization "A. K." <minforth@arcor.de> - 2020-09-21 02:12 -0700
      Re: Algorithm Optimization "Johann 'Myrkraverk' Oskarsson" <johann@myrkraverk.com> - 2021-04-21 16:29 +0000
  Re: Algorithm Optimization "mwmarkland@gmail.com" <mwmarkland@gmail.com> - 2020-09-16 07:57 -0700
    Re: Algorithm Optimization "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2020-09-16 11:44 -0400
    Re: Algorithm Optimization gah4 <gah4@u.washington.edu> - 2020-09-16 13:59 -0700
      Re: Algorithm Optimization Thomas Koenig <tkoenig@netcologne.de> - 2020-09-17 06:39 +0000
  Re: Algorithm Optimization Hans-Peter Diettrich <DrDiettrich1@netscape.net> - 2020-12-13 23:13 +0100
    Re: Algorithm Optimization gah4 <gah4@u.washington.edu> - 2020-12-20 22:45 -0800

csiph-web