Note the difference between:
numbers.inject(0) {| sum, x | sum + x } |
.vs.
sum = 0 numbers.each {| x | sum += x } sum |
… the former is obviously preferred.
However:
If the #inject result value is mutated *and* the result value is used elsewhere (or implicitly returned), use a local variable with #each, instead of #inject.
My colleague, David, had an interesting problem:
For example, if an error should occur 33% of the time, it should be predictable like: ERROR, ok, ok, ERROR, ok, ok, ...
Or at 50% error rate: ERROR, ok, ERROR, ok, ...“
devdriven:
p(t) in range [0,1) at time t and P is the probability of the event (e.g. I/O error) then: event?(t) = p(t) < P.
Pseudo-random numbers are predictable if you know the seed."
David:
In some programming languages, asynchronous events can occur at any time.
For instance, in Ruby, there are subclasses of Exception that can be raised at any time — there are few lines of code safe from interruption. Some of exceptions, due to their cause, are not recoverable at all.
http://code.google.com/p/rubyenterpriseedition/issues/detail?id=67
Use mmap() to allocate heaps by default.
Use mmap() MAP_ANON, instead of /dev/zero.
Align mmap() size to pagesize.
Align heap allocation size to pagesize.
Expand heap slotlimit to fit in aligned allocation.
New $RUBY_HEAP_* options:
RUBY_HEAP_INIT_SLOTS=N
initial number of slots per heap.
RUBY_HEAP_MIN_SLOTS=N
value is independent of RUBY_HEAP_INIT_SLOTS.
RUBY_HEAP_MAX_SLOTS=N
max number slots for a heap.
RUBY_HEAP_PAGESIZE=bytes
defaults to PAGESIZE or 4096.
RUBY_HEAP_SLOTS_INCREMENT=N
allow 0.
Refactor set_gc_parameters().
This patch reduces the stack buffer memory footprint of dead Threads as early as possible, rather than waiting until the Thread can be GCed.
This is applicable only to the zero-copy context switch patch.
http://code.google.com/p/rubyenterpriseedition/issues/detail?id=57
http://blog.phusion.nl/2011/02/12/ruby-enterprise-edition-1-8-7-2011-01-released/
The slides from my ChicagoRuby 2010/05/04 presentation :
http://kurtstephens.com/pub/ruby/ruby_code_tweaks/
All the raw data used to generate the graph should be referenced in the slides.
The code used to generate the slides is here:
http://github.com/kstephens/ruby_code_tweaks
I’m looking to increase the set of code “Problems” to cover other tiny code idioms and platform issues, for example: regular expressions, numerics, etc. If you have ideas, take a look at the code and contact me.
Justin Love gave a fantastic presentation on lambda and closure.
Thanks to everyone who came — hope it was helpful.
Video from the talk:
Ruby Code Performance Tweaks by Kurt Stephens from ChicagoRuby on Vimeo.
Ruby rational.rb clean-up and the Fixnum#gcd primitive was refactored into a new MRI extension. Fixnum#gcd is now defined during require ‘rational’.
This dramatically improves performance of Ruby Date class.
http://svn.ruby-lang.org/cgi-bin/viewvc.cgi/branches/ruby_1_8/ChangeLog?…
http://redmine.ruby-lang.org/issues/show/2561
See https://devdriven.com/2007/03/ruby-date-rational-fixnumgcd-hack-increased-app-performance-by-15/ .
This should also speed up DateTime. This will not help 1.9 performance.
The attached file is based on MRI 1.8.6 rational.rb.
> ruby rational_performance.rb
user system total real
test_it 32.930000 3.030000 35.960000 ( 35.971832)
test_it 33.840000 2.910000 36.750000 ( 36.758585)
test_it ks_rational 29.110000 2.460000 31.570000 ( 31.572762)
Overview:
case x; when Foo; ...; end is faster than if Foo.kind_of?(x).return in tail position."#{x}/#{y}" is faster than x.to_s + "/" + y.to_s.#-, #zero?, #nonzero? natively.#abs returns self if > 0.MRI 1.8.7 patch to follow shortly.