Re: Object-relational impedence

From: David Cressey <>
Date: Mon, 10 Mar 2008 18:06:55 GMT
Message-ID: <3NeBj.1997$dK3.931_at_trndny03>

"Marshall" <> wrote in message

> >
> Ah, SICP. Did you know that David Cressey's name appears
> in it? Apparently he was at ground zero in the early days of
> garbage collection, and coined a term that is still used. I told
> that story when my languages discussion group had
> Mr. Abelson for lunch.

I don't think of 1971, when I wrote the garbage collector for MDL as "the early days of garbage collection." The "early days would have been in the 1950s when McCarthy wrote the garbage collector for LISP. The MDL garbage collector was more ambitious than the Lisp garbage collector. But I had the advantage of learning from the work that had already been done.

What made the MDL garbage collector more ambitious was that we supported a data structure called a "vector" that was addressable via the PDP-10 address arithmetic. The use of a random access structure was 1000 times faster than the use of a linked list, for some of the things we wanted to do. The use of hardware address arithmetic made it even faster. The consequence of support for vectors was that the garbage collector had to not only reclaim unused space, but defragment it as well.

Somebody who came along after me got a PhD by rewriting the MDL garbage collector so that it could do its work in the background, without suspending all the MDL execution threads. I have no idea how such a thing would have worked.

> Marshall
> PS. Name dropping alert!!! I try to resist, but I am weak.

Thanks! Normally the only people who drop my name are the people who cull mailing lists of "important people". Received on Mon Mar 10 2008 - 19:06:55 CET

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