/ 
Bencher-Scenarios-PERLANCAR-0.06
River stage one • 1 direct dependent • 1 total dependent
/ Bencher::Scenario::PERLANCAR::require

NAME

Bencher::Scenario::PERLANCAR::require - Benchmark require() in a tight loop/subroutine

VERSION

This document describes version 0.06 of Bencher::Scenario::PERLANCAR::require (from Perl distribution Bencher-Scenarios-PERLANCAR), released on 2017-01-25.

SYNOPSIS

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.

DESCRIPTION

require() can be put inside a block (like a subroutine) to delay loading a module:

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.

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.

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.

BENCHMARK PARTICIPANTS

  • baseline_empty_sub (perl_code)

    Code template:

  • require_in_sub (perl_code)

    Code template:

    require File::Find

  • require_in_sub_pm (perl_code)

    There is no effect of using the path form.

    Code template:

    require "File/Find.pm"

  • require_in_state (perl_code)

    Code template:

    state $dummy = do { require File::Find }

SAMPLE BENCHMARK RESULTS

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):

#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.

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/Bencher-Scenarios-PERLANCAR.

SOURCE

Source repository is at https://github.com/perlancar/perl-Bencher-Scenarios-PERLANCAR.

BUGS

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.

AUTHOR

perlancar <perlancar@cpan.org>

COPYRIGHT AND LICENSE

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.