From: Brian Candler <b.candler@...>
Date: 2008-09-22T23:08:20+09:00
Subject: Re: for or each?

Sylvain Joyeux wrote:
> To cut down the discussion,
> ObjectSpace#each_object does *not* give you those, so you can't count
> them with it.

OK, I see that certain objects are not yielded, including T_SCOPE.

On the other hand, observe that the following program doesn't leak 
memory:

  def foo
    :dummy
  end

  GC.disable
  (1..10_000_000).each { |i| foo }
  puts `ps auxwww | grep ruby | grep -v grep`
  puts "Press enter"
  STDIN.gets

On the two machines I tried the RSS is 3MB, regardless of how big I make 
the loop. (That's 1.8.4 stock Ubuntu Dapper, and 1.8.6p114 compiled from 
source)

So are you sure a scope is created every time round the loop - not just 
on the first invocation?

The following program *does* consume memory:

  def foo
    :dummy
  end

  GC.disable
  (1..1_000_000).each { |x|
    (1..1).each { |y| foo }
  }
  puts `ps auxwww | grep ruby | grep -v grep`
  puts "Press enter"
  STDIN.gets

That is: I'm happy to accept that every time the inner loop starts, it 
creates a new scope (since the block is a closure with a different value 
of x bound to it)

But if I change the inner loop to

    (1..10).each { |y| foo }

the memory consumption is the same. So whether a block is invoked once 
or 10 times makes no difference to memory usage.
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