Re: Baby X is bor nagain

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Sujet : Re: Baby X is bor nagain
De : david.brown (at) *nospam* hesbynett.no (David Brown)
Groupes : comp.lang.c
Date : 24. Jun 2024, 10:28:52
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <v5bao4$r66u$2@dont-email.me>
References : 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
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On 24/06/2024 02:56, Scott Lurndal wrote:
bart <bc@freeuk.com> writes:
On 24/06/2024 00:52, Malcolm McLean wrote:
 
43 seconds compile time is getting to be a bit of a problem. But not for
the final build. Only for intermediate builds.
>
That isn't the issue here (it could have been 4.3 seconds vs 1.7 seconds).
>
David Brown was claiming there was little difference (15%, although on
the 34.3s and 30.8s timings, it is actually 11% not 15%) between
optimised and unoptimised builds, whereas I have always seen substantial
differences like 100% or more.
I think the main problem is that Bart doesn't understand what "builds" are.  And he doesn't understand the relevance - or irrelevance - of compile times while developing software, and how they relate to /build/ times or /development/ time.  I don't care how long it takes to compile a file - I care how long the build takes.

 David is likely referring to the average.
I think in this case it was just estimating percentages in my head, rounding up - it's all approximate.

 You've obviously found
an outlier.   I've one outlier that compiles with -O0 in about
15 seconds, and with -O3 it takes 8 minutes.    However, the
code in that file is far from optimal.  The rest of the source
files in that project (20+ million lines) are more in the 10-15%
range, if that high.
 I took a look at the outlier, and got rid of some unnecessary
local block declarations in a large function, removed some unnecessary
#include's and cut the -O3 time in half, to just under 4
minutes.  The variable tracking feature of the gnu compiler
collection seems to be the culprit here.
 
Some optimisations scale quadratically or worse, by code size and/or complexity.  And using -O3 rather than -O2 will enable optimisation passes that can take a lot longer while usually only having minor benefits to the generated code, and indeed risking giving worse results.   So some types of code can take an inordinate amount of time to compile with -O3.  Typical cases are very large files or files with very large functions - C code generated by other tools (such as simulators generated from HDL languages) can often be problematic.  If it matters, it's normally possible to do some fine-tuning with particular optimisation passes or fiddling optimiser parameters.

Date Sujet#  Auteur
11 Jun 24 * Baby X is bor nagain322Malcolm McLean
11 Jun 24 +* Re: Baby X is bor nagain3bart
11 Jun 24 i`* Re: Baby X is bor nagain2Malcolm McLean
12 Jun 24 i `- Mac users (Was: Baby X is bor nagain)1Kenny McCormack
11 Jun 24 +* Re: Baby X is bor nagain4Ben Bacarisse
11 Jun 24 i`* Re: Baby X is bor nagain3Malcolm McLean
12 Jun 24 i `* Re: Baby X is bor nagain2Ben Bacarisse
12 Jun 24 i  `- Re: Baby X is bor nagain1Malcolm McLean
11 Jun 24 +* Re: Baby X is bor nagain313Bonita Montero
11 Jun 24 i+* Re: Baby X is bor nagain309Malcolm McLean
12 Jun 24 ii`* Re: Baby X is bor nagain308Bonita Montero
12 Jun 24 ii +* Re: Baby X is bor nagain305David Brown
12 Jun 24 ii i+* Re: Baby X is bor nagain2Malcolm McLean
12 Jun 24 ii ii`- Re: Baby X is bor nagain1David Brown
12 Jun 24 ii i+- Re: Baby X is bor nagain1Bonita Montero
12 Jun 24 ii i`* Re: Baby X is bor nagain301bart
12 Jun 24 ii i +* Re: Baby X is bor nagain4Bonita Montero
12 Jun 24 ii i i`* Re: Baby X is bor nagain3bart
12 Jun 24 ii i i `* Re: Baby X is bor nagain2Bonita Montero
12 Jun 24 ii i i  `- Re: Baby X is bor nagain1bart
12 Jun 24 ii i `* Re: Baby X is bor nagain296David Brown
12 Jun 24 ii i  `* Re: Baby X is bor nagain295Michael S
13 Jun 24 ii i   +- Re: Baby X is bor nagain1Malcolm McLean
13 Jun 24 ii i   `* Re: Baby X is bor nagain293David Brown
13 Jun 24 ii i    +* Re: Baby X is bor nagain5bart
13 Jun 24 ii i    i+* Re: Baby X is bor nagain3tTh
13 Jun 24 ii i    ii`* Re: Baby X is bor nagain2bart
14 Jun 24 ii i    ii `- Re: Baby X is bor nagain1Bonita Montero
13 Jun 24 ii i    i`- Re: Baby X is bor nagain1Michael S
13 Jun 24 ii i    `* Re: Baby X is bor nagain287Michael S
14 Jun 24 ii i     +* Re: Baby X is bor nagain3David Brown
14 Jun 24 ii i     i`* Re: Baby X is bor nagain2bart
15 Jun 24 ii i     i `- Re: Baby X is bor nagain1David Brown
17 Jun 24 ii i     `* Re: Baby X is bor nagain283James Kuyper
17 Jun 24 ii i      +* Re: Baby X is bor nagain86Kaz Kylheku
17 Jun 24 ii i      i+- Are Javascript and Python similarly slow ? (Was: Baby X is bor nagain)1Michael S
17 Jun 24 ii i      i+* Re: Baby X is bor nagain2Michael S
18 Jun 24 ii i      ii`- Re: Baby X is bor nagain1Tim Rentsch
17 Jun 24 ii i      i+* Re: Baby X is bor nagain80David Brown
18 Jun 24 ii i      ii`* Re: Baby X is bor nagain79Michael S
18 Jun 24 ii i      ii `* Re: Baby X is bor nagain78David Brown
18 Jun 24 ii i      ii  +* Re: Baby X is bor nagain7bart
18 Jun 24 ii i      ii  i`* Re: Baby X is bor nagain6David Brown
18 Jun 24 ii i      ii  i +* Re: Baby X is bor nagain2bart
18 Jun 24 ii i      ii  i i`- Re: Baby X is bor nagain1David Brown
18 Jun 24 ii i      ii  i `* Re: Baby X is bor nagain3DFS
18 Jun 24 ii i      ii  i  `* Re: Baby X is bor nagain2Mark Bourne
18 Jun 24 ii i      ii  i   `- Re: Baby X is bor nagain1DFS
18 Jun 24 ii i      ii  +* Re: Baby X is bor nagain3Malcolm McLean
18 Jun 24 ii i      ii  i+- Re: Baby X is bor nagain1David Brown
18 Jun 24 ii i      ii  i`- Re: Baby X is bor nagain1Mark Bourne
18 Jun 24 ii i      ii  `* Re: Baby X is bor nagain67Michael S
18 Jun 24 ii i      ii   +* Re: Baby X is bor nagain65Malcolm McLean
19 Jun 24 ii i      ii   i+* Re: Baby X is bor nagain59Keith Thompson
19 Jun 24 ii i      ii   ii`* Re: Baby X is bor nagain58Malcolm McLean
19 Jun 24 ii i      ii   ii +* Re: Baby X is bor nagain56David Brown
19 Jun 24 ii i      ii   ii i`* Re: Baby X is bor nagain55Malcolm McLean
19 Jun 24 ii i      ii   ii i `* Re: Baby X is bor nagain54David Brown
19 Jun 24 ii i      ii   ii i  `* Re: Baby X is bor nagain53Malcolm McLean
19 Jun 24 ii i      ii   ii i   +* Re: Baby X is bor nagain10bart
20 Jun 24 ii i      ii   ii i   i`* Re: Baby X is bor nagain9David Brown
20 Jun 24 ii i      ii   ii i   i `* Re: Baby X is bor nagain8bart
20 Jun 24 ii i      ii   ii i   i  `* Re: Baby X is bor nagain7David Brown
20 Jun 24 ii i      ii   ii i   i   `* Re: Baby X is bor nagain6bart
20 Jun 24 ii i      ii   ii i   i    +* Re: Baby X is bor nagain2Michael S
20 Jun 24 ii i      ii   ii i   i    i`- Re: Baby X is bor nagain1bart
20 Jun 24 ii i      ii   ii i   i    `* Re: Baby X is bor nagain3David Brown
21 Jun 24 ii i      ii   ii i   i     `* Re: Baby X is bor nagain2bart
21 Jun 24 ii i      ii   ii i   i      `- Re: Baby X is bor nagain1David Brown
20 Jun 24 ii i      ii   ii i   `* Re: Baby X is bor nagain42David Brown
20 Jun 24 ii i      ii   ii i    `* Re: Baby X is bor nagain41Malcolm McLean
20 Jun 24 ii i      ii   ii i     +- Re: Baby X is bor nagain1David Brown
20 Jun 24 ii i      ii   ii i     `* Re: Baby X is bor nagain39Ben Bacarisse
20 Jun 24 ii i      ii   ii i      +* Re: Baby X is bor nagain2Malcolm McLean
20 Jun 24 ii i      ii   ii i      i`- Re: Baby X is bor nagain1Ben Bacarisse
20 Jun 24 ii i      ii   ii i      +* Re: Baby X is bor nagain9Tim Rentsch
20 Jun 24 ii i      ii   ii i      i`* Re: Baby X is bor nagain8Malcolm McLean
20 Jun 24 ii i      ii   ii i      i +* Re: Baby X is bor nagain2James Kuyper
20 Jun 24 ii i      ii   ii i      i i`- Re: Baby X is bor nagain1Keith Thompson
20 Jun 24 ii i      ii   ii i      i +- Re: Baby X is bor nagain1Vir Campestris
20 Jun 24 ii i      ii   ii i      i +* Re: Baby X is bor nagain2Keith Thompson
21 Jun 24 ii i      ii   ii i      i i`- Re: Baby X is bor nagain1vallor
21 Jun 24 ii i      ii   ii i      i +- Re: Baby X is bor nagain1Tim Rentsch
21 Jun 24 ii i      ii   ii i      i `- Re: Baby X is bor nagain1David Brown
20 Jun 24 ii i      ii   ii i      `* Re: Baby X is bor nagain27Keith Thompson
20 Jun 24 ii i      ii   ii i       `* Re: Baby X is bor nagain26Ben Bacarisse
20 Jun 24 ii i      ii   ii i        +* Re: Baby X is bor nagain2Michael S
21 Jun 24 ii i      ii   ii i        i`- Re: Baby X is bor nagain1Ben Bacarisse
20 Jun 24 ii i      ii   ii i        +- Re: Baby X is bor nagain1Keith Thompson
21 Jun 24 ii i      ii   ii i        +* Re: Baby X is bor nagain2James Kuyper
21 Jun 24 ii i      ii   ii i        i`- Re: Baby X is bor nagain1Keith Thompson
22 Jun 24 ii i      ii   ii i        `* Re: Baby X is bor nagain20Tim Rentsch
23 Jun 24 ii i      ii   ii i         `* Re: Baby X is bor nagain19Ben Bacarisse
23 Jun 24 ii i      ii   ii i          +* Re: Baby X is bor nagain9James Kuyper
23 Jun 24 ii i      ii   ii i          i`* Re: Baby X is bor nagain8Tim Rentsch
24 Jun 24 ii i      ii   ii i          i +* Re: Baby X is bor nagain4Ben Bacarisse
24 Jun 24 ii i      ii   ii i          i i`* Re: Baby X is bor nagain3Tim Rentsch
25 Jun 24 ii i      ii   ii i          i i `* Re: Baby X is bor nagain2Ben Bacarisse
25 Jun 24 ii i      ii   ii i          i i  `- Re: Baby X is bor nagain1Tim Rentsch
24 Jun 24 ii i      ii   ii i          i `* Re: Baby X is bor nagain3Keith Thompson
24 Jun 24 ii i      ii   ii i          i  `* Re: Baby X is bor nagain2Tim Rentsch
23 Jun 24 ii i      ii   ii i          `* Re: Baby X is bor nagain9Tim Rentsch
19 Jun 24 ii i      ii   ii `- Re: Baby X is bor nagain1Keith Thompson
19 Jun 24 ii i      ii   i`* Re: Baby X is bor nagain5David Brown
19 Jun 24 ii i      ii   `- Re: Baby X is bor nagain1David Brown
18 Jun 24 ii i      i+- Re: Baby X is bor nagain1James Kuyper
20 Jun 24 ii i      i`- Re: Baby X is bor nagain1Vir Campestris
17 Jun 24 ii i      +* Re: Baby X is bor nagain193bart
17 Jun 24 ii i      `* Re: Baby X is bor nagain3Malcolm McLean
12 Jun 24 ii `* Topicality is not your strong suit (Was: Baby X is bor nagain)2Kenny McCormack
11 Jun 24 i`* Re: Baby X is bor nagain3bart
11 Jun 24 `- Re: Baby X is bor nagain1Kalevi Kolttonen

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