From: Dan Sugalski <[EMAIL PROTECTED]> Date: Fri, 29 Apr 2005 15:23:47 -0400
At 10:55 PM -0400 4/28/05, Bob Rogers wrote: > From: Robin Redeker <[EMAIL PROTECTED]> >I'm astounded. Do neither of you ever design data structures with >symmetrical parent<->child pointers? No trees with parents? No >doubly-linked lists? In my (probably skewed) experience, circular >references are used frequently in languages like C or Lisp that don't >penalize them.
I responded to Uri on this, but note that I said "neither are terribly common", and they aren't. Relative to the total number of GC-able things, objects in circular structures are a very small minority.
I can think of many programs I've written or otherwise hacked on where this is not the case. In some cases, the majority of objects are directly circular (i.e. part of a cycle as opposed to being referenced from an object in a cycle). But I suppose that just means that we've worked on very different apps. Before Perl5, I used to use parent pointers at the drop of a hat. But, 'nuff said, I guess.
Actually I think you'll find that isn't the case, though it's easy to overlook, and is probably mostly my sloppy terminology. Programs, when they run, tend to create a lot of what I've been calling objects, but for parrot they'd be PMCs, and not necessarily actually real objects as such.
Languages parrot's going for -- perl, python, ruby, php, tcl, and their ilk -- do chew through a lot temps. For the GC's purposes, and mine, they count. When you add those in, the plain GCable thing count tends to skyrocket. Yeah, the *important* data structures in a program may be partly, or mostly, in circular structures, but the hundred thousand temps that get created to hold intermediate values are all uncircular things. This is definitely not the case for languages like C++ where you're a lot closer to the metal, but we're a bit further away from it here. (It'd be interesting, since parrot *can* keep stats, to run some complex programs and see what the GC numbers look like. I ought to turn it on for some of the longer-running reports I have and see what there is to see, though the results may be as much a condemnation of my compiler as anything else. :)
--
Dan
--------------------------------------it's like this-------------------
Dan Sugalski even samurai
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