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User Questions
perl process slower and slower when loop number increase
No replies — Read more | Post response
by Anonymous Monk
on Jan 22, 2018 at 03:20
    Hi Monks,

    I have these simple one liner tests in my CentOS 7 vps box

    1a. test perl loop with $i=10 $ time perl -e 'for($i=0;$i<=10;$i++){}' real 0m0.003s user 0m0.000s sys 0m0.000s 1b. test PHP loop with $i=10 $ time php -r 'for($i=0;$i<=10;$i++){}' real 0m0.027s user 0m0.020s sys 0m0.004s in average test 1a and 1b, perl is 9x or 10x faster than PHP ------------------------------------------------------------ 2a. test perl loop with $i=10000 $ time perl -e 'for($i=0;$i<=10000;$i++){}' real 0m0.005s user 0m0.004s sys 0m0.000s 2b. test PHP loop with $i=10000 $ time php -r 'for($i=0;$i<=10000;$i++){}' real 0m0.027s user 0m0.024s sys 0m0.000s in test 2a and 2b, perl still much faster than PHP ------------------------------------------------------------ 3a. test perl loop with $i=1000000 $ time perl -e 'for($i=0;$i<=1000000;$i++){}' real 0m0.091s user 0m0.088s sys 0m0.000s 3b. test PHP loop with $i=1000000 $ time php -r 'for($i=0;$i<=1000000;$i++){}' real 0m0.045s user 0m0.044s sys 0m0.004s in test 3a and 3b, PHP already faster then perl ------------------------------------------------------------ now, use extreme loop number like all benchmark code in alioth benchmark game: 4a. test perl loop with $i=100000000 $ time perl -e 'for($i=0;$i<=100000000;$i++){}' real 0m7.310s user 0m7.304s sys 0m0.000s 4b. test PHP loop with $i=100000000 $ time php -r 'for($i=0;$i<=100000000;$i++){}' real 0m1.624s user 0m1.616s sys 0m0.004s in test 4a and 4b, PHP is much much faster then perl

    I already try compare with java, node, and c and the result same as result above, more loop number make loop slower but not as extreme slower as perl

    Is there any setting or ENV to make perl loop faster for big number like test above ?

Sorting and ranking
5 direct replies — Read more / Contribute
by Anonymous Monk
on Jan 21, 2018 at 06:32
    Hi Monks
    I would like your wisdom regarding why my code below does not work:
    Task : from the given hash, rank the keys based on the values, also taking into account that if 2 or more keys have the same value, the get the same ranking.
    my %data = ( 'car' => 180, 'motorcycle' => 150, 'skate' => 150, 'bird' => 120, ); my @keys = keys %data; my @sorted[ sort { $data{$keys[$b]} <=> $data{$keys[$a]} } 0..$#keys ] + = 1..@keys; my $rank = 1; my @ranks = (); foreach $count (0..$#sorted) { $rank = $count + 1 if ($count > 0 && $sorted[$count] != $sorted[$c +ount - 1]); push @ranks, $rank; } print join ",", @ranks;

    The code prints 1,2,3,4, while it should print 1,2,2,3 since motorcycle and skate have the same value. Also, could you tell me how I can also print the key next to its ranking (motorcycle, skate etc)?
    Many thanks!
Set a variable in calling package
5 direct replies — Read more / Contribute
by TerryBerry
on Jan 20, 2018 at 21:25

    I'm trying to figure out how to set a variable in the calling package that use's a package.

    That question might not have been entirely clear, so let me provide an example. Consider the following three files:

    --- #!/usr/bin/perl -w use strict; use lib './'; use MyPackage; --- package MyBase; use strict; use Utils; # return true 1; --- package MyPackage; use strict; # export use base 'Exporter'; our @EXPORT = qw{mysub}; # import sub import { # what goes here to set $var in the caller package? # E.g. $MyPackage::var # export symbols MyPackage->export_to_level(1, @_); } # some subroutine sub mysub { # how do I access $var in the caller package? # E.g. $MyPackage::var } # return true 1;
    Here's what I want to happen. When MyPackage uses Utils, Utils create a variable in MyPackage which can be accessed as $MyPackage::var. Furthermore, mysub() needs to be able to get to that variable when it's called. Of course, Utils doesn't know the name of the caller until, y'know, it's called, so I can't just hardcode in a package name.

    I think I could muck out a solution using a lot of evals, but that seems like it would be very inefficient. Something a little more in keeping with how symbol tables work seems like a better solution.

Generate list of possibilities from incomplete input
3 direct replies — Read more / Contribute
by Pascal666
on Jan 20, 2018 at 19:25

    Given a string containing 9 hexadecimal characters, I need to generate a list of all possible 10 character hexadecimal strings that contain the given 9 characters in order. The list need not be in any specific order.

    I think the complete list will have 16x10=160 items, but 9 of those will be duplicates. Don't worry about removing the duplicates, but if your solution doesn't include them that is fine too.

    Obviously, this can be done with a couple nested loops and string concatenation. Somehow, that just doesn't feel like the best way to me though.

    For example, given 0ae4bb830, the list would include:

    00ae4bb830 10ae4bb830 20ae4bb830 30ae4bb830 40ae4bb830 50ae4bb830 60ae4bb830 70ae4bb830 80ae4bb830 90ae4bb830 a0ae4bb830 b0ae4bb830 c0ae4bb830 d0ae4bb830 e0ae4bb830 f0ae4bb830 00ae4bb830* 01ae4bb830 02ae4bb830 03ae4bb830 04ae4bb830 ...
What does Test::LeakTrace do?
1 direct reply — Read more / Contribute
by TerryBerry
on Jan 20, 2018 at 16:53

    Could you nice folks clarify what Test::LeakTrace does and what problems it finds? I wonder if I misunderstand because it's giving me errors for very, very simple code. Or maybe there are some very simple things about Perl I've been doing wrong all these years. You decide (then tell me).

    Consider this code:

    #!/usr/bin/perl -w use strict; use Test::LeakTrace; # test for leak leaktrace { require './'; }; is, well, almost empty:
    Here's the output from running the script:
    leaked SCALAR(0x558ad5e37f40) from ./ line 7.

    It seems weird to me to get any kind of memory leak for such a very basic script.

    Here's my perl version:

    This is perl 5, version 26, subversion 0 (v5.26.0) built for x86_64-li +nux-gnu-thread-multi (with 56 registered patches, see perl -V for more detail)

    I'm running on Ubuntu Linux 17.10.

Multiple params
3 direct replies — Read more / Contribute
by htmanning
on Jan 20, 2018 at 15:05

    I'm missing something here. I have a link with 2 params, (cell and target_dir).

    use CGI qw(:standard); use CGI 'param'; $store = new CGI; $cell = $store->param('cell'); $target_dir = $store->param('target_dir');

    The link looks like this:

    All I get from the script is the target_dir. I'm not getting the cell returned. What am I doing wrong?

Excel or Perl for simple statistics?
3 direct replies — Read more / Contribute
by Anonymous Monk
on Jan 20, 2018 at 08:22
    Dear Monks,
    I want to do a few basic statistics (mean and stdev) and since I have lots of data I figured I would do it with Perl (using the Statistics::Basic module). However, I notice some quite interesting discrepancies as opposed to if I calculated the same values using Excel's formulas. Particularly I think the stdev is a problem, since in one test run I did, I got 0.401 with Excel and 0.41 with the Perl module, which does affect my calculations later on.
    Do you have any comment on that?
POST API in Perl using LWP::UserAgent with authentication providing errors
2 direct replies — Read more / Contribute
by ssara
on Jan 20, 2018 at 06:32

    Hello, I am trying to use POST method in perl to send information to an API. I would like to call the below api which requires following inputs:



    Currency: (optional) The currency symbol of the balance to return e.g. 'DOT' (not required if 'CurrencyId' supplied)

    CurrencyId: (optional) The Cryptopia currency identifier of the balance to return e.g. '2' (not required if 'Currency' supplied).

    Request Structure:


    API_KEY: Your Cryptopia api key

    URI: the request uri. e.g.

    HASHED_POST_PARAMS: Base64 encoded MD5 hash of the post parameters

    NONCE: unique indicator for each request.

    Below is my code snippet:

    use LWP::UserAgent; use JSON; use Digest::MD5 qw(md5); use Digest::SHA qw(hmac_sha256_base64); use MIME::Base64; my $api_key ='PUBLIC KEY'; my $api_private_key ='PRIVATE KEY'; my $ua = LWP::UserAgent->new; my $url = ""; my %req = ( Currency => "PAC" ); my $nonce = int(rand(1000000)); my $post_data = encode_json(\%req); my $post_data_enc = encode_base64(md5($post_data)); my $req_signature = sprintf("%sPOST%s%s%s", $api_key, lc(urlencode($ur +l)), $nonce, $post_data_enc); # Sign request signature with private key. my $req_signature_hmac = hmac_sha256_base64($req_signature, decode_bas +e64($api_private_key)); # Generate value for 'Authorization' header field. my $auth_header_value = sprintf("amx %s:%s:%s", $api_key, $req_signatu +re_hmac, $nonce); my $response = $ua->post($url, Content => $post_data, 'Content-Type' => 'application/json', 'charset' => 'utf-8', Authorization => $auth_header_value ); die "Request failed: ", $response->content unless $response->is_succes +s(); print $response->content, $/; sub urlencode { my $s = shift; $s =~ s/ /+/g; $s =~ s/([^A-Za-z0-9\+-])/sprintf("%%%02X", ord($1))/seg; return $s; }

    This code gives the following error: {"Success":false,"Error":"Signature does not match request parameters."}.

    I have also checked the PUBLIC and PRIVATE key and it works when i use a java or php code. But when I am doing with perl it just provides me error. Please can you help me on providing pointers.

    Thank You in advance. POST_MAX not working
4 direct replies — Read more / Contribute
by adjuvant
on Jan 19, 2018 at 15:37

    I've been searching the web and playing with my code for a while now and can't find a solution to this problem.

    I would like to limit uploads to my site with CGI. I'm setting $CGI::POST_MAX = 1024 * 1024 * 20; for a 20 Mb limit, but when I test it with a 900 Mb file, the upload goes through just fine. I've tried every modification I can think of including moving the $CGI::POST_MAX statement around, changing use CGI; to use CGI qw( :standard ); and updating using CPAN. I now have version 4.38 of installed. I would welcome any ideas to be able to protect my server from DDoS attacks.

    Here is my code snippet:

    #!/usr/bin/perl -T my $version = "0.1"; use strict; use warnings; use CGI; use CGI::Carp qw/fatalsToBrowser/; $CGI::POST_MAX = 1024 * 1024 * 20; # maximum upload filesize is 20M $| = 1; my $q = CGI->new; print $q->header; print $q->start_html(-title=>"mysite", -style=>{-src=>'/plasma/style.css'}); print $q->start_multipart_form(-method=>'POST', -action=>'/cgi-bin/start_analysis.cgi') +; print $q->filefield(-name=>"uf_core", -size=>20); print "\tFile type: "; print $q->popup_menu(-name=>"urt", -values=>['fasta','genbank'], -default=>'fasta'); print "<br><br>"; print qq{<input type="file" name="uf_qry" size="20" multiple="true" /> +}; print "<br>"; print $q->submit(-value=>"ANALYZE!"); print $q->end_multipart_form; print $q->end_html;
How to strip comments and whitespace from a regex defined with /x?
5 direct replies — Read more / Contribute
by jh
on Jan 19, 2018 at 14:27

    I would like to print out some previously-defined regular expressions in a compact format. The main thing I want to do is strip out the whitespace and comments from those defined with the /x modifier. So if I have two functionally identical regexes:

    our $rgx_plain = qr/^([a-z]+)\d*$/; our $rgx_fancy = qr/ ^ # beginning of string ( # begin cap $1 [a-z]+ # one or more letters ) # end cap $1 \d* # optional digits $ # end of string /x;

    then I'd like to make a function clean_regex such that

    say $rgx_plain; say clean_regex($rgx_fancy);

    both print the same thing. Ideally clean_regex is a no-op on regexes defined without the /x modifier, such that

    say clean_regex($rgx_plain);

    also prints the same thing. I have hacked together something gross and terrible but I was hoping for something better, presumably asking the Regexp compiler what it has once it's done throwing away comments and whitespace.


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