[31962] in Perl-Users-Digest
Perl-Users Digest, Issue: 3226 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Fri Dec 3 03:09:35 2010
Date: Fri, 3 Dec 2010 00:09:15 -0800 (PST)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Fri, 3 Dec 2010 Volume: 11 Number: 3226
Today's topics:
Re: Optimisation for tight loops... <schaitan@gmail.com>
Re: Optimisation for tight loops... <uri@StemSystems.com>
Re: Optimisation for tight loops... <hjp-usenet2@hjp.at>
Re: Optimisation for tight loops... <kst-u@mib.org>
Re: Optimisation for tight loops... <uri@StemSystems.com>
Re: Optimisation for tight loops... <marc.girod@gmail.com>
Re: Optimisation for tight loops... <hjp-usenet2@hjp.at>
Re: Optimisation for tight loops... <kst-u@mib.org>
Re: Optimisation for tight loops... <uri@StemSystems.com>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@seesig.invalid
work to heal <r@thevoid1.net>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Thu, 2 Dec 2010 11:14:20 -0800 (PST)
From: Krishna Chaitanya <schaitan@gmail.com>
Subject: Re: Optimisation for tight loops...
Message-Id: <b24c76f1-a645-4b7f-b91a-a70202edfb49@v17g2000prc.googlegroups.com>
Hi all, thanks for the criticism of my poor choice of operators as
well as test cases. I appreciate your time and wisdom.
One last question - in the ocean of Perl literature and documentation,
is there any one single place where points similar to what you've
raised in your replies are mentioned (rather explicitly)? Like, for
example, the choice of operators and the consequences in terms of
speed, etc? My situation is: I don't have a lot of time to go through
a large body of knowledge as other concerns are pressing...and can
hardly afford a Perl expert's time. I know this might invite a lot of
flak from those who love to do things the right way...but, if you can
help me, I'd be grateful.
------------------------------
Date: Thu, 02 Dec 2010 14:36:45 -0500
From: "Uri Guttman" <uri@StemSystems.com>
Subject: Re: Optimisation for tight loops...
Message-Id: <87tyiw0xwy.fsf@quad.sysarch.com>
>>>>> "KC" == Krishna Chaitanya <schaitan@gmail.com> writes:
KC> One last question - in the ocean of Perl literature and
KC> documentation, is there any one single place where points similar
KC> to what you've raised in your replies are mentioned (rather
KC> explicitly)? Like, for example, the choice of operators and the
KC> consequences in terms of speed, etc? My situation is: I don't have
KC> a lot of time to go through a large body of knowledge as other
KC> concerns are pressing...and can hardly afford a Perl expert's
KC> time. I know this might invite a lot of flak from those who love
KC> to do things the right way...but, if you can help me, I'd be
KC> grateful.
there is a reason it is called expertise and that there are
experts. experts are the ones who write the docs that you don't have the
time to read. there are no shortcuts to becoming an expert. google for
'10000 hour expert'
uri
--
Uri Guttman ------ uri@stemsystems.com -------- http://www.sysarch.com --
----- Perl Code Review , Architecture, Development, Training, Support ------
--------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------
------------------------------
Date: Thu, 2 Dec 2010 21:51:07 +0100
From: "Peter J. Holzer" <hjp-usenet2@hjp.at>
Subject: Re: Optimisation for tight loops...
Message-Id: <slrnifg1lr.669.hjp-usenet2@hrunkner.hjp.at>
On 2010-12-02 18:35, Uri Guttman <uri@StemSystems.com> wrote:
>>>>>> "KC" == Krishna Chaitanya <schaitan@gmail.com> writes:
>
> KC> " If you are searching for an element in a list, it can be more
> KC> efficient to store the data in a hash structure, and then simply look
> KC> to see whether the key is defined, rather than to loop through the
> KC> entire array using grep() for instance. " (from perlperf)
>
> anyone here could have told you that.
Why should he ask here if it's already in the docs? Aren't we constantly
telling people to read the docs? Now somebody does and you're chewing
him out for it.
hp
------------------------------
Date: Thu, 02 Dec 2010 13:02:28 -0800
From: Keith Thompson <kst-u@mib.org>
Subject: Re: Optimisation for tight loops...
Message-Id: <lnwrnropln.fsf@nuthaus.mib.org>
"Uri Guttman" <uri@StemSystems.com> writes:
>>>>>> "KT" == Keith Thompson <kst-u@mib.org> writes:
>
> >> no dynamic lang (and i assume it is the others are who are badmouthing
> >> perl) can do loop unrolling and such. this is because things can change
> >> at runtime with tied things, symrefs, and eval string. no compiler can
> >> handle such things and optimize them out of a loop or unroll a loop.
>
> KT> Why not? Perl is compiled before it's executed, after all, and
> KT> the compiler *could* determine that the body of a loop doesn't do
> KT> anything disruptive and use that information to perform optimizations
> KT> (loop unrolling, common subexpression elimination, etc.).
>
> KT> It's not at all clear that it makes sense to do so, given that
> KT> you're going to pay the overhead each time the program is executed.
> KT> And I have no idea what optimizations the perl implementation
> KT> actually performs. But I suggest that your "no dynamic lang"
> KT> claim is overstated.
>
> then why haven't you ever seen any dynamic lang do any of the classic
> loop optimizations you see in classic compiled langs like fortran?
For one thing, because I haven't looked. Aside from that, I don't
know for sure, but it's likely because such optimizations are too
difficult, are too seldom applicable, and have too little payoff,
for them to be worth the effort.
> you
> can't. loop unrolling and constant subexpression expression moving can't
> be done if the values can change underneath as they can in a language
> like perl. a sub call which can be chosen at runtime in the loop can
> change the WHOLE loop by calling eval. and that can't be detected. any
> variable in the loop could be tied which is a runtime thing and that
> could call anything which could change the loop. no compiler can see or
> predict those sorts of things. perl does constant folding, conversions
> of constant style subs (as what the constant pragma does) to real
> constants and not much else. those things can't have variables or
> anything other than pure constants at compile time.
Consider this complete program:
#!/usr/bin/perl
use strict;
use warnings;
my $i = 0;
for (1 .. 10) {
$i ++;
}
print "$i\n";
The Perl compiler/interpreter can see the entire program before it
produces any output. At least in principle, it *could* analyze it
and determine that $i isn't tied, that there are no sub calls in the
loop, that there are no calls to eval(), and so forth. Given that
information, it *could* compile the whole thing to the equivalent of
print "10\n";
In this particular case, the time spent doing the analysis and code
transformation would certainly exceed the time saved by simplifying the
code. And in general, I'm not arguing that perl *should* do this kind
of thing, just that it's not impossible.
Even in a static compiled language like C, certain constructs can
inhibit certain optimizations. A optimizing C compiler could likely
reduce something like the above to puts("10"), but would not be able to
do so if the loop body took the address of i or called an external
function. Perl, as you point out, has more constructs that can
interfere with this kind of analysis. That doesn't make the analysis
impossible in every case.
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
------------------------------
Date: Thu, 02 Dec 2010 16:15:47 -0500
From: "Uri Guttman" <uri@StemSystems.com>
Subject: Re: Optimisation for tight loops...
Message-Id: <87mxon27wc.fsf@quad.sysarch.com>
>>>>> "KT" == Keith Thompson <kst-u@mib.org> writes:
KT> "Uri Guttman" <uri@StemSystems.com> writes:
>> >> no dynamic lang (and i assume it is the others are who are badmouthing
>> >> perl) can do loop unrolling and such. this is because things can change
>> >> at runtime with tied things, symrefs, and eval string. no compiler can
>> >> handle such things and optimize them out of a loop or unroll a loop.
>> then why haven't you ever seen any dynamic lang do any of the classic
>> loop optimizations you see in classic compiled langs like fortran?
KT> For one thing, because I haven't looked. Aside from that, I don't
KT> know for sure, but it's likely because such optimizations are too
KT> difficult, are too seldom applicable, and have too little payoff,
KT> for them to be worth the effort.
loop optimizations are an ancient technique that probably got invented
in the 60's if not earlier. it is well known by all compiler people. it
isn't even that complicated to do. perl COULD do it if it made sense as
it just involves scanning the opcode tree for invariant sections in
loops and moving them before the loop. loop unrolling is also a common
thing. perl can't do them not because of the lack of skill but because
the language won't allow it. you can't compile and know what will happen
at runtime which can screw up the optimizations. so it isn't even
discussed let alone attempted.
KT> Consider this complete program:
KT> #!/usr/bin/perl
KT> use strict;
KT> use warnings;
KT> my $i = 0;
KT> for (1 .. 10) {
KT> $i ++;
KT> }
KT> print "$i\n";
KT> The Perl compiler/interpreter can see the entire program before it
KT> produces any output. At least in principle, it *could* analyze it
KT> and determine that $i isn't tied, that there are no sub calls in the
KT> loop, that there are no calls to eval(), and so forth. Given that
KT> information, it *could* compile the whole thing to the equivalent of
and what if warnings was replaced by a trojan module that made declaring
$i a tied variable?
KT> Even in a static compiled language like C, certain constructs can
KT> inhibit certain optimizations. A optimizing C compiler could likely
KT> reduce something like the above to puts("10"), but would not be able to
KT> do so if the loop body took the address of i or called an external
KT> function. Perl, as you point out, has more constructs that can
KT> interfere with this kind of analysis. That doesn't make the analysis
KT> impossible in every case.
it is impossible. that is the win and loss of a dynamic language. if you
could analyze it completely in advance, you could also solve the halting
problem. and even if it were possible, it isn't worth the effort as that
deep of an analysis is equivilent to running the program (see halting
problem).
uri
--
Uri Guttman ------ uri@stemsystems.com -------- http://www.sysarch.com --
----- Perl Code Review , Architecture, Development, Training, Support ------
--------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------
------------------------------
Date: Thu, 2 Dec 2010 13:31:04 -0800 (PST)
From: Marc Girod <marc.girod@gmail.com>
Subject: Re: Optimisation for tight loops...
Message-Id: <79bf922c-85ae-4e6d-aa83-e4eced982c67@p1g2000yqm.googlegroups.com>
On Dec 2, 9:15=A0pm, "Uri Guttman" <u...@StemSystems.com> wrote:
> and what if warnings was replaced by a trojan module that made declaring
> $i a tied variable?
Do you mean that perl doesn't compile warnings from the sources at
this stage?
Because if it does, it knows at compile time.
Marc
------------------------------
Date: Thu, 2 Dec 2010 22:40:26 +0100
From: "Peter J. Holzer" <hjp-usenet2@hjp.at>
Subject: Re: Optimisation for tight loops...
Message-Id: <slrnifg4ia.669.hjp-usenet2@hrunkner.hjp.at>
On 2010-12-02 18:43, Uri Guttman <uri@StemSystems.com> wrote:
>>>>>> "KT" == Keith Thompson <kst-u@mib.org> writes:
>
> >> no dynamic lang (and i assume it is the others are who are
> >> badmouthing perl) can do loop unrolling and such. this is because
> >> things can change at runtime with tied things, symrefs, and eval
> >> string. no compiler can handle such things and optimize them out
> >> of a loop or unroll a loop.
>
> KT> Why not? Perl is compiled before it's executed, after all, and
> KT> the compiler *could* determine that the body of a loop doesn't do
> KT> anything disruptive and use that information to perform optimizations
> KT> (loop unrolling, common subexpression elimination, etc.).
>
> KT> It's not at all clear that it makes sense to do so, given that
> KT> you're going to pay the overhead each time the program is executed.
> KT> And I have no idea what optimizations the perl implementation
> KT> actually performs. But I suggest that your "no dynamic lang"
> KT> claim is overstated.
>
> then why haven't you ever seen any dynamic lang do any of the classic
> loop optimizations you see in classic compiled langs like fortran?
Mostly because it's not worth it. Loop unrolling is a technique that
works well for real CPUs because jumps are expensive (or rather, they
were expensive - I'm not sure if loop unrolling is still worthwhile on
modern CPUs), but that doesn't apply to typical bytecode interpreters.
Here's a simple example. A loop which fills an array with a constant
value:
#!/usr/bin/perl
use warnings;
use strict;
use Benchmark qw(:hireswallclock timethese cmpthese);
my @a;
my $results = timethese(-3, {
normal => sub {
for (0 .. 999_999) {
$a[$_] = 0;
}
},
unroll4 => sub {
for (0 .. 249_999) {
$a[$_ * 4 + 0] = 0;
$a[$_ * 4 + 1] = 0;
$a[$_ * 4 + 2] = 0;
$a[$_ * 4 + 3] = 0;
}
},
unroll4c => sub {
my $c = 0;
for (0 .. 249_999) {
$a[$c++] = 0;
$a[$c++] = 0;
$a[$c++] = 0;
$a[$c++] = 0;
}
},
}
);
cmpthese($results);
__END__
Rate unroll4 unroll4c normal
unroll4 4.04/s -- -33% -37%
unroll4c 6.00/s 49% -- -6%
normal 6.37/s 58% 6% --
The result is not surprising: The unrolled versions are slower.
The extra computations more than make up for the lower loop overhead.
In machine code, special addressing modes could be used in "unroll4"
instead of the explicit multiplication and addition, or the computations
could be performed in parallel to the memory accesses. Similarly in
"unroll4c".
> you can't. loop unrolling and constant subexpression expression moving
> can't be done if the values can change underneath as they can in a
> language like perl.
Most of the time the values don't change underneath, and
in many cases this could be detected by the compiler. But such analysis
is expensive. When the program is compiled on every run, this is hard to
amortize, even if there is a noticable speedup, which doesn't seem to be
the case for loop unrolling.
There are other techniques which are cheaper and gain more, for example JIT.
hp
------------------------------
Date: Thu, 02 Dec 2010 17:59:02 -0800
From: Keith Thompson <kst-u@mib.org>
Subject: Re: Optimisation for tight loops...
Message-Id: <lnpqtjobvd.fsf@nuthaus.mib.org>
"Uri Guttman" <uri@StemSystems.com> writes:
>>>>>> "KT" == Keith Thompson <kst-u@mib.org> writes:
[...]
> KT> Consider this complete program:
>
> KT> #!/usr/bin/perl
>
> KT> use strict;
> KT> use warnings;
>
> KT> my $i = 0;
> KT> for (1 .. 10) {
> KT> $i ++;
> KT> }
> KT> print "$i\n";
>
> KT> The Perl compiler/interpreter can see the entire program before it
> KT> produces any output. At least in principle, it *could* analyze it
> KT> and determine that $i isn't tied, that there are no sub calls in the
> KT> loop, that there are no calls to eval(), and so forth. Given that
> KT> information, it *could* compile the whole thing to the equivalent of
>
> and what if warnings was replaced by a trojan module that made declaring
> $i a tied variable?
Then the hypothetical loop-optimizing Perl implementation would
analyze the contents of warnings.pm, fail to prove that it doesn't
do anything disruptive, and refrain from performing the optimization.
But if warnings *isn't* replaced by a Trojan module, the
implementation can, in principle, detect that fact.
Or, if you prefer, consider a program like the above but without
the "use strict; use warnings;" (and invoked without using perl's
-m or -M option or equivalent).
> KT> Even in a static compiled language like C, certain constructs can
> KT> inhibit certain optimizations. A optimizing C compiler could likely
> KT> reduce something like the above to puts("10"), but would not be able to
> KT> do so if the loop body took the address of i or called an external
> KT> function. Perl, as you point out, has more constructs that can
> KT> interfere with this kind of analysis. That doesn't make the analysis
> KT> impossible in every case.
>
> it is impossible. that is the win and loss of a dynamic language. if you
> could analyze it completely in advance, you could also solve the halting
> problem.
That doesn't follow. The halting problem is about the impossibility
of doing certain kinds of analysis on *all* programs. You are
claiming that certain kinds of analysis are impossible on *any*
programs, a much stronger claim.
The halting theorem doesn't imply that you can't prove the "hello,
world" program terminates.
> and even if it were possible, it isn't worth the effort as that
> deep of an analysis is equivilent to running the program (see halting
> problem).
No, it isn't, at least not in all cases. *I* can look at the above
program and conclude that it will print "10" followed by a new-line.
I don't have to run the program to reach that conclusion, and it
wouldn't take me 100 times as long if the 10 were changed to 1000.
There's no reason a compiler can't perform the same analysis *for
at least some programs*.
(Note that I'm not arguing that it *is* worth the effort, merely that
your argument that it isn't is incorrect.)
And who knows, *maybe* there are some loop optimizations that would
be worth doing in Perl, at least optionally.
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
------------------------------
Date: Thu, 02 Dec 2010 21:09:32 -0500
From: "Uri Guttman" <uri@StemSystems.com>
Subject: Re: Optimisation for tight loops...
Message-Id: <87ei9z1uar.fsf@quad.sysarch.com>
>>>>> "KT" == Keith Thompson <kst-u@mib.org> writes:
KT> "Uri Guttman" <uri@StemSystems.com> writes:
>>>>>>> "KT" == Keith Thompson <kst-u@mib.org> writes:
KT> [...]
KT> Consider this complete program:
>>
KT> #!/usr/bin/perl
>>
KT> use strict;
KT> use warnings;
>>
KT> my $i = 0;
KT> for (1 .. 10) {
KT> $i ++;
KT> }
KT> print "$i\n";
>>
KT> The Perl compiler/interpreter can see the entire program before it
KT> produces any output. At least in principle, it *could* analyze it
KT> and determine that $i isn't tied, that there are no sub calls in the
KT> loop, that there are no calls to eval(), and so forth. Given that
KT> information, it *could* compile the whole thing to the equivalent of
>>
>> and what if warnings was replaced by a trojan module that made declaring
>> $i a tied variable?
KT> Then the hypothetical loop-optimizing Perl implementation would
KT> analyze the contents of warnings.pm, fail to prove that it doesn't
KT> do anything disruptive, and refrain from performing the optimization.
and if that module loads another module? ad infinitum. welcome to the
halting problem. do you even know what that is?
KT> That doesn't follow. The halting problem is about the impossibility
KT> of doing certain kinds of analysis on *all* programs. You are
KT> claiming that certain kinds of analysis are impossible on *any*
KT> programs, a much stronger claim.
no, it is the same problem. you have to keep analyzing deeper and
deeper. the issue isn't about small things being optimized, it is how
much work you need to do to gain a worthy optimization. you have already
exceeded that limit.
KT> (Note that I'm not arguing that it *is* worth the effort, merely that
KT> your argument that it isn't is incorrect.)
no, it is the same. we can easily write a solution for the halting
problem for most programs. same as for analyzing code for
optimization. that doesn't mean you solved the problem nor have you
found a proper limit on when to stop. someone (like you! :) will always
bitch that the analysis doesn't go deeply enough for your
program. better to not even offer to do it.
uri
--
Uri Guttman ------ uri@stemsystems.com -------- http://www.sysarch.com --
----- Perl Code Review , Architecture, Development, Training, Support ------
--------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------
------------------------------
Date: Fri, 03 Dec 2010 01:58:46 -0600
From: tadmc@seesig.invalid
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
Message-Id: <Lf-dnfQDj_KrPmXRnZ2dnUVZ5tqdnZ2d@giganews.com>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
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Social faux pas to avoid
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Be extra cautious when you get upset
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- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
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Question should be about Perl, not about the application area
It can be difficult to separate out where your problem really is,
but you should make a conscious effort to post to the most
applicable newsgroup. That is, after all, where you are the most
likely to find the people who know how to answer your question.
Being able to "partition" a problem is an essential skill for
effectively troubleshooting programming problems. If you don't get
that right, you end up looking for answers in the wrong places.
It should be understood that you may not know that the root of your
problem is not Perl-related (the two most frequent ones are CGI and
Operating System related), so off-topic postings will happen from
time to time. Be gracious when someone helps you find a better place
to ask your question by pointing you to a more applicable newsgroup.
How to participate (post) in the clpmisc community
Carefully choose the contents of your Subject header
You have 40 precious characters of Subject to win out and be one of
the posts that gets read. Don't waste them. Take care while
composing them, they are the key that opens the door to getting an
answer.
Spend them indicating what aspect of Perl others will find if they
should decide to read your article.
Do not spend them indicating "experience level" (guru, newbie...).
Do not spend them pleading (please read, urgent, help!...).
Do not spend them on non-Subjects (Perl question, one-word
Subject...)
For more information on choosing a Subject see "Choosing Good
Subject Lines":
http://www.cpan.org/authors/id/D/DM/DMR/subjects.post
Part of the beauty of newsgroup dynamics, is that you can contribute
to the community with your very first post! If your choice of
Subject leads a fellow Perler to find the thread you are starting,
then even asking a question helps us all.
Use an effective followup style
When composing a followup, quote only enough text to establish the
context for the comments that you will add. Always indicate who
wrote the quoted material. Never quote an entire article. Never
quote a .signature (unless that is what you are commenting on).
Intersperse your comments *following* each section of quoted text to
which they relate. Unappreciated followup styles are referred to as
"top-posting", "Jeopardy" (because the answer comes before the
question), or "TOFU" (Text Over, Fullquote Under).
Reversing the chronology of the dialog makes it much harder to
understand (some folks won't even read it if written in that style).
For more information on quoting style, see:
http://web.presby.edu/~nnqadmin/nnq/nquote.html
Speak Perl rather than English, when possible
Perl is much more precise than natural language. Saying it in Perl
instead will avoid misunderstanding your question or problem.
Do not say: I have variable with "foo\tbar" in it.
Instead say: I have $var = "foo\tbar", or I have $var = 'foo\tbar',
or I have $var = <DATA> (and show the data line).
Ask perl to help you
You can ask perl itself to help you find common programming mistakes
by doing two things: enable warnings (perldoc warnings) and enable
"strict"ures (perldoc strict).
You should not bother the hundreds/thousands of readers of the
newsgroup without first seeing if a machine can help you find your
problem. It is demeaning to be asked to do the work of a machine. It
will annoy the readers of your article.
You can look up any of the messages that perl might issue to find
out what the message means and how to resolve the potential mistake
(perldoc perldiag). If you would like perl to look them up for you,
you can put "use diagnostics;" near the top of your program.
Do not re-type Perl code
Use copy/paste or your editor's "import" function rather than
attempting to type in your code. If you make a typo you will get
followups about your typos instead of about the question you are
trying to get answered.
Provide enough information
If you do the things in this item, you will have an Extremely Good
chance of getting people to try and help you with your problem!
These features are a really big bonus toward your question winning
out over all of the other posts that you are competing with.
First make a short (less than 20-30 lines) and *complete* program
that illustrates the problem you are having. People should be able
to run your program by copy/pasting the code from your article. (You
will find that doing this step very often reveals your problem
directly. Leading to an answer much more quickly and reliably than
posting to Usenet.)
Describe *precisely* the input to your program. Also provide example
input data for your program. If you need to show file input, use the
__DATA__ token (perldata.pod) to provide the file contents inside of
your Perl program.
Show the output (including the verbatim text of any messages) of
your program.
Describe how you want the output to be different from what you are
getting.
If you have no idea at all of how to code up your situation, be sure
to at least describe the 2 things that you *do* know: input and
desired output.
Do not provide too much information
Do not just post your entire program for debugging. Most especially
do not post someone *else's* entire program.
Do not post binaries, HTML, or MIME
clpmisc is a text only newsgroup. If you have images or binaries
that explain your question, put them in a publically accessible
place (like a Web server) and provide a pointer to that location. If
you include code, cut and paste it directly in the message body.
Don't attach anything to the message. Don't post vcards or HTML.
Many people (and even some Usenet servers) will automatically filter
out such messages. Many people will not be able to easily read your
post. Plain text is something everyone can read.
Social faux pas to avoid
The first two below are symptoms of lots of FAQ asking here in clpmisc.
It happens so often that folks will assume that it is happening yet
again. If you have looked but not found, or found but didn't understand
the docs, say so in your article.
Asking a Frequently Asked Question
It should be understood that you may have missed the applicable FAQ
when you checked, which is not a big deal. But if the Frequently
Asked Question is worded similar to your question, folks will assume
that you did not look at all. Don't become indignant at pointers to
the FAQ, particularly if it solves your problem.
Asking a question easily answered by a cursory doc search
If folks think you have not even tried the obvious step of reading
the docs applicable to your problem, they are likely to become
annoyed.
If you are flamed for not checking when you *did* check, then just
shrug it off (and take the answer that you got).
Asking for emailed answers
Emailed answers benefit one person. Posted answers benefit the
entire community. If folks can take the time to answer your
question, then you can take the time to go get the answer in the
same place where you asked the question.
It is OK to ask for a *copy* of the answer to be emailed, but many
will ignore such requests anyway. If you munge your address, you
should never expect (or ask) to get email in response to a Usenet
post.
Ask the question here, get the answer here (maybe).
Beware of saying "doesn't work"
This is a "red flag" phrase. If you find yourself writing that,
pause and see if you can't describe what is not working without
saying "doesn't work". That is, describe how it is not what you
want.
Sending a "stealth" Cc copy
A "stealth Cc" is when you both email and post a reply without
indicating *in the body* that you are doing so.
Be extra cautious when you get upset
Count to ten before composing a followup when you are upset
This is recommended in all Usenet newsgroups. Here in clpmisc, most
flaming sub-threads are not about any feature of Perl at all! They
are most often for what was seen as a breach of netiquette. If you
have lurked for a bit, then you will know what is expected and won't
make such posts in the first place.
But if you get upset, wait a while before writing your followup. I
recommend waiting at least 30 minutes.
Count to ten after composing and before posting when you are upset
After you have written your followup, wait *another* 30 minutes
before committing yourself by posting it. You cannot take it back
once it has been said.
AUTHOR
Tad McClellan and many others on the comp.lang.perl.misc newsgroup.
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.liamg\100cm.j.dat/"
The above message is a Usenet post.
I don't recall having given anyone permission to use it on a Web site.
------------------------------
Date: Thu, 2 Dec 2010 15:10:15 -0800 (PST)
From: Robin <r@thevoid1.net>
Subject: work to heal
Message-Id: <a4cce452-c172-4688-9079-51170613513a@l17g2000yqe.googlegroups.com>
work on stuff to heal for very long periods.....-r
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
Administrivia:
To submit articles to comp.lang.perl.announce, send your article to
clpa@perl.com.
Back issues are available via anonymous ftp from
ftp://cil-www.oce.orst.edu/pub/perl/old-digests.
#For other requests pertaining to the digest, send mail to
#perl-users-request@ruby.oce.orst.edu. Do not waste your time or mine
#sending perl questions to the -request address, I don't have time to
#answer them even if I did know the answer.
------------------------------
End of Perl-Users Digest V11 Issue 3226
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