From: Ron Jeffries <ronjeffries@...>
Date: 2002-03-07T04:36:06+09:00
Subject: object size and overhead.

My set program was turned loose yesterday to build a hundred thousand objects.
Here's the code:

  def testLots
    set = Set.empty
    (0..99999).each { | i | 
      set.insertUniqueAt(i,makeR1) 
    }
  end

  def makeR1
    r1 = Set.fromArray
    r1.insertAt('name', 'jeffries')
    r1.insertAt('state', 'MI')
    r1
  end

The Set.from array has two arrays inside that basically hold the 'name', 'state'
items and the 'jeffries' 'MI' items. So the Set created has two instance
variables, an array of scopes and one of elements. It looks like this.

#<EnumeratedSet:0x2ae5ee0
 @scopes=["name", "state"], @elements=["jeffries", "MI"]>

Running this thing at 100,000 records uses 60 megs of memory. 

I see 7 objects per set, so 60,000,000 / 600,000 = 100 bytes per object, which
seems a bit rough.

So my question is ... what's the overhead in a Ruby object. And my second
question is: ask what I /should/ have asked and answer that too.

Thanks!

Ronald E Jeffries
http://www.XProgramming.com
http://www.objectmentor.com
I'm giving the best advice I have. You get to decide whether it's true for you.