Bencher::Scenario::PERLANCAR::require - Benchmark require() in a tight loop/subroutine
This document describes version 0.06 of Bencher::Scenario::PERLANCAR::require (from Perl distribution Bencher-Scenarios-PERLANCAR), released on 2017-01-25.
To run benchmark with default option:
% bencher -m PERLANCAR::require
For more options (dump scenario, list/include/exclude/add participants, list/include/exclude/add datasets, etc), see bencher or run bencher --help.
bencher --help
require() can be put inside a block (like a subroutine) to delay loading a module:
require()
sub foo { require Some::Module; ... }
After a module is loaded, the next require() should be cheap enough: it just checks against %INC to see if an entry for the module is there. So it should just be the cost of a single hash lookup.
%INC
However, for very tight loops/subroutines, you can avoid (reduce) this cost by putting the require() inside a state variable, which will cause the require() to be evaluated just once:
sub foo { state $dummy = do { require Some::Module }; ... }
There is a per-sub-invocation cost too of setting up the state variable $dummy. But this cost is several times smaller.
$dummy
Or, alternatively, you might also want to decide to put the require() statement outside of the block/subroutine.
Packaging a benchmark script as a Bencher scenario makes it convenient to include/exclude/add participants/datasets (either via CLI or Perl code), send the result to a central repository, among others . See Bencher and bencher (CLI) for more details.
baseline_empty_sub (perl_code)
Code template:
require_in_sub (perl_code)
require File::Find
require_in_sub_pm (perl_code)
There is no effect of using the path form.
require "File/Find.pm"
require_in_state (perl_code)
state $dummy = do { require File::Find }
Run on: perl: v5.24.0, CPU: Intel(R) Core(TM) M-5Y71 CPU @ 1.20GHz (2 cores), OS: GNU/Linux LinuxMint version 17.3, OS kernel: Linux version 3.19.0-32-generic.
Benchmark with default options (bencher -m PERLANCAR::require):
bencher -m PERLANCAR::require
#table1# +--------------------+------------+-----------+------------+---------+---------+ | participant | rate (/s) | time (ns) | vs_slowest | errors | samples | +--------------------+------------+-----------+------------+---------+---------+ | require_in_sub_pm | 17000000 | 57 | 1 | 2.1e-10 | 20 | | require_in_sub | 17700000 | 56.6 | 1.01 | 5.2e-11 | 20 | | require_in_state | 140000000 | 7.2 | 7.9 | 2.6e-11 | 20 | | baseline_empty_sub | -150000000 | -6.5 | -8.8 | 6.3e-11 | 20 | +--------------------+------------+-----------+------------+---------+---------+
To display as an interactive HTML table on a browser, you can add option --format html+datatables.
--format html+datatables
Please visit the project's homepage at https://metacpan.org/release/Bencher-Scenarios-PERLANCAR.
Source repository is at https://github.com/perlancar/perl-Bencher-Scenarios-PERLANCAR.
Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Bencher-Scenarios-PERLANCAR
When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.
perlancar <perlancar@cpan.org>
This software is copyright (c) 2017 by perlancar@cpan.org.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
To install Bencher::Scenarios::PERLANCAR, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Bencher::Scenarios::PERLANCAR
CPAN shell
perl -MCPAN -e shell install Bencher::Scenarios::PERLANCAR
For more information on module installation, please visit the detailed CPAN module installation guide.