Small optimization tips

[Vincent Foley]

Hello all,

I was working on a little script earlier, which I thought was too slow
for my taste. It's now about 5-6x faster than it originally was.
Normally, this would've been enough, but being very curious about Ruby,
I tried to make it go even faster by using micro optimizations. Here
are some things I found out:

* Running your script with the -rprofile option is the first thing you
should do
* Using a Set instead of an Array when you only want to store unique
values can help make your code go faster
* Disabling the GC can slightly increase the speed of your script.
However, I don't think it's a good idea to use in larger applications

That's a few things I found out today. Does anyone else have quick
optimization tips?

 

[Robert Klemme]

Hello all,

I was working on a little script earlier, which I thought was too slow
for my taste. It's now about 5-6x faster than it originally was.
Normally, this would've been enough, but being very curious about Ruby,
I tried to make it go even faster by using micro optimizations. Here
are some things I found out:

* Running your script with the -rprofile option is the first thing you
should do

... if it's too slow.

* Using a Set instead of an Array when you only want to store unique
values can help make your code go faster

IMHO this is not a micro optimization, this is a changed design. A set
represents something entirely different from an array (although they
share some properties).

* Disabling the GC can slightly increase the speed of your script.
However, I don't think it's a good idea to use in larger applications

I don't think either.

That's a few things I found out today. Does anyone else have quick
optimization tips?

In no particular order: Create as few objects as possible. Watch out
where you can in place modifying methods of string vs. non bang
methods. Choose the appropriate abstractions. Don't prematurely
optimize.

Kind regards

robert

 

[Shea Martin]

In no particular order: Create as few objects as possible. Watch out
where you can in place modifying methods of string vs. non bang
methods. Choose the appropriate abstractions. Don't prematurely
optimize.

Just clarification: you are saying in-place is faster right?
~S

 

[John Carter]

That's a few things I found out today. Does anyone else have quick
optimization tips?

instead of this...

open( file_name) do |inf|
inf.each_line do |line|
line.chomp! # Optimization Tip, use chomp! instead of
# line = line.chomp
next unless line =~ %r{Looks right}x
#do stuff
end
end

try...

File.read( file_name).scan(%r{ what I'm actually looking for}mx) do |m|
# Do _stuff
end

Much much faster!

Always remember change of algorithm can get you 2 orders of magnitude
speed, optimization tweaks usually around factors 1.5

No code is faster than No Code.

Native code is very much faster than Ruby.

eg. I wrote a ring buffer class in Ruby but found unless it grew to about
2000 elements using Array.shift and unshift was faster.

Benchmark class is the the optimizers friend.

John Carter Phone : (64)(3) 358 6639
Tait Electronics Fax : (64)(3) 359 4632
PO Box 1645 Christchurch Email : (e-mail address removed)
New Zealand

Carter's Clarification of Murphy's Law.

"Things only ever go right so that they may go more spectacularly wrong later."

From this principle, all of life and physics may be deduced.

 

[Vincent Foley]

I have something else that is probably common knowledge: if you can
avoid using regular expressions, do it. By replacing the regex matches
in my script with string operations, I increased the runtime speed by a
factor of ~4.

 

[James Edward Gray II]

I have something else that is probably common knowledge: if you can
avoid using regular expressions, do it. By replacing the regex
matches
in my script with string operations, I increased the runtime speed
by a
factor of ~4.

However, if you can replace a few Ruby operations with one
complicated search and replace, sometimes it works the other way. It
depends on the problem.

James Edward Gray II

 

[Robert Klemme]

Just clarification: you are saying in-place is faster right?

Right. But not applicable everywhere (i.e. if you're not allowed to modify
something or do not know whether something is frozen...).

Kind regards

robert

 

[John Carter]

That's a few things I found out today. Does anyone else have quick
optimization tips?

Use ruby-1.9 it is faster.
Compile with gcc-4.1
Optimize

CC=gcc-4.1 CFLAGS='-march=pentium4 -O3 -fomit-frame-pointer' CPP=cpp-4.1 \
CXXFLAGS='-march=pentium4 -O3 -fomit-frame-pointer' 'CXX=g++-4.1' \
/configure
make


Warning, this may be hazardous for your health, but it works for me.

ps. Anyone worked out how to use gcc profile feedback to build a faster
ruby yet?


John Carter Phone : (64)(3) 358 6639
Tait Electronics Fax : (64)(3) 359 4632
PO Box 1645 Christchurch Email : (e-mail address removed)
New Zealand

Carter's Clarification of Murphy's Law.

"Things only ever go right so that they may go more spectacularly wrong later."

From this principle, all of life and physics may be deduced.

 

[Eric Hodel]

Use ruby-1.9 it is faster.
Compile with gcc-4.1
Optimize

CC=gcc-4.1 CFLAGS='-march=pentium4 -O3 -fomit-frame-pointer'
CPP=cpp-4.1 \
CXXFLAGS='-march=pentium4 -O3 -fomit-frame-pointer' 'CXX=g++-4.1' \
./configure
make


Warning, this may be hazardous for your health, but it works for me.

You don't want to compile with -fomit-frame-pointer. See [ruby-core:
7660]