It Doesn't Matter
London -- 25th November 2017
Paul Johnson
@pjcjohnson
www.pjcj.net
In regione caecorum rex est luscus
Fast
Best
How?
How do I do X?
Use method A
But method B is faster
Let me benchmark!
Benchmark
Rate Method A Method B
Method A 1298701/s -- -24%
Method B 1703578/s 31% --
So we should use method B?
Not so fast!
Is the benchmark correct?
1. Benchmarking is hard
2. Benchmarking is hard
Why do we use Perl?
Succint
Powerful
CPAN
Tools
Blazingly fast
Unicode
Blazingly fast
Trade runtime speed for development speed
Benchmark
Rate Method A Method B
Method A 1298701/s -- -24%
Method B 1703578/s 31% --
This is not the bottleneck you are looking for
So we should use method B?
Rules of optimisation
Rules of optimisation
Michael A. Jackson
Rules of optimisation
Rule 1: Don't do it.
Michael A. Jackson
Michael A. Jackson
Rules of optimisation
Rule 1: Don't do it.
Rule 2 (for experts only): Don't do it yet.
Michael A. Jackson
Rule 2 (for experts only): Don't do it yet.
Michael A. Jackson
Does it work?
Is it fast enough?
Are you sure?
Profile!
Fix your algorithm
Throw hardware
Cache something
Count the ops
How do I increment an array?
How do I increment an array?
map { $_ = $_ + 1 } @a
How do I increment an array?
map { $_ = $_ + 1 } @a
map { $_++ } @a
How do I increment an array?
map { $_ = $_ + 1 } @a
map { $_++ } @a
map $_++, @a
How do I increment an array?
map { $_ = $_ + 1 } @a
map { $_++ } @a
map $_++, @a
for (@a) { $_++ }
How do I increment an array?
map { $_ = $_ + 1 } @a
map { $_++ } @a
map $_++, @a
for (@a) { $_++ }
$_++ for @a
How do I increment an array?
map { $_ = $_ + 1 } @a
map { $_++ } @a
map $_++, @a
for (@a) { $_++ }
$_++ for @a
++$_ for @a
It Doesn't Matter!