Re: Struct is slow

On 16.10.2007 19:05, Alex Fenton wrote:
Wayne Magor wrote:
I have a script in which I was using a 2-element array where a struct
would be used in another language, so I decided to give the Ruby class
Struct a try.

My script went from taking 2 seconds to taking 27 seconds from this
simple change!

This doesn't sound likely, even if your script did nothing else but use the Struct class. I'd look elsewhere for the source of slowness (try running your script with -rprofile).

A quick benchmark suggests that Struct is somewhat slower to instantiate (+100%), marginally slower to set values in (+33%), and the same speed to fetch values from as an Array:

BENCHMARK:

require 'benchmark'

GC.disable
Foo = Struct.new(:foo, :bar)

repetitions = 500_000

puts 'struct-init', Benchmark::measure {
repetitions.times { f = Foo.new('x', 666) }
}

puts 'array-init', Benchmark::measure {
repetitions.times { f = ['x', 666] }
}

puts 'struct-get', Benchmark::measure {
f = Foo.new('x', 666)
repetitions.times { g = f.foo }
}

puts 'array-get', Benchmark::measure {
f = ['x', 666]
repetitions.times { g = f[0] }
}

puts 'struct-set', Benchmark::measure {
f = Foo.new('x', 666)
repetitions.times { f.foo = 'y' }
}

puts 'array-set', Benchmark::measure {
f = ['x', 666]
repetitions.times { f[0] = 'y' }
}


__END__

RESULTS (ruby 1.8.4 (2005-12-24) [i386-mswin32])

struct-init
1.359000 0.031000 1.390000 ( 1.390000)
array-init
0.563000 0.016000 0.579000 ( 0.579000)
struct-get
0.281000 0.000000 0.281000 ( 0.281000)
array-get
0.297000 0.000000 0.297000 ( 0.297000)
struct-set
0.422000 0.000000 0.422000 ( 0.422000)
array-set
0.281000 0.000000 0.281000 ( 0.281000)

I'm not sure whether you are familiar with Benchmark#bmbm which does a rehearsal - personally I rather not switch off GC since in realistic situations GC time belongs into the mix. But results are rather similar:

Robert@Babelfish2 /cygdrive/c/TEMP
$ ruby array-struct.rb
Rehearsal --------------------------------------------------
struct init 3.812000 0.000000 3.812000 ( 3.923000)
array init 1.672000 0.000000 1.672000 ( 1.709000)
struct get 0.437000 0.000000 0.437000 ( 0.440000)
array get 0.485000 0.000000 0.485000 ( 0.485000)
struct set 0.718000 0.000000 0.718000 ( 0.716000)
array set 0.500000 0.000000 0.500000 ( 0.510000)
----------------------------------------- total: 7.624000sec

user system total real
struct init 3.891000 0.000000 3.891000 ( 3.984000)
array init 1.640000 0.000000 1.640000 ( 1.690000)
struct get 0.438000 0.000000 0.438000 ( 0.450000)
array get 0.469000 0.000000 0.469000 ( 0.469000)
struct set 0.703000 0.000000 0.703000 ( 0.715000)
array set 0.484000 0.000000 0.484000 ( 0.504000)

Robert@Babelfish2 /cygdrive/c/TEMP
$ cat array-struct.rb
require 'benchmark'

REP = 500_000

Foo = Struct.new :foo, :bar

data = "foo"
c1 = Foo.new data, data
c2 = [data, data]

Benchmark.bmbm 15 do |x|
x.report 'struct init' do
REP.times { Foo.new data, data }
end

x.report 'array init' do
REP.times { [data, data] }
end

x.report 'struct get' do
REP.times { c1.bar }
end

x.report 'array get' do
REP.times { c2[1] }
end

x.report 'struct set' do
REP.times { c1.bar = data }
end

x.report 'array set' do
REP.times { c2[1] = data }
end
end

Kind regards

robert
.

Relevant Pages

  • Re: [PATCH] console UTF-8 fixes
    ... At least please put them in a separate .c file and include a script to ... rbtree is an excellent data structure if you have to modify ... +static int bisearch(uint32_t ucs, const struct interval *table, int max) ...
    (Linux-Kernel)
  • Re: C++ Compiler with a -Wwarn-use-of-strcpy or similar option??
    ... > I need to automatically search and replace all fixed size ... > detect use of a strcpy to a buffer of fixed size. ... > struct x X; ... > provided the script can be guaranteed that the replacement is valid ...
    (comp.lang.cpp)
  • Re: Array of structures
    ... > u> Can JScript use a COM object that is an array of structures? ... The proper way to expose such a thing to scripting would be ... > no problem of accessing it from a script. ... The struct has POD types like this: ...
    (microsoft.public.scripting.jscript)
  • Re: Using ruby hash on array
    ... Struct is an automatic way to define a simple class. ... least in 1.8.7 AFAIK) an initialize method. ... puts m.instance_var ... printf "%20s %6d\n", a, cnt ...
    (comp.lang.ruby)
  • Re: Anyone have the perl unpack template for wtmp?
    ... I've looked through the utmp headers and can't quite get the unpack ... When I run the script using simple print ... > template or see what I've done wrong with my template? ... # This is the C struct from utmp.h, which was need to configure the ...
    (comp.sys.hp.hpux)