[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: SUN vs Lisp machine hardware differences?

    Date: Tue, 11 Aug 87 17:38 EDT
    From: Daniel L. Weinreb <DLW@ALDERAAN.SCRC.Symbolics.COM>

	Date: Tue, 11 Aug 87 13:54:26 PDT
	From: larus%paris.Berkeley.EDU@berkeley.edu (James Larus)

	Cdr-coding was proposed and justify in the mid-1970's when memory
	prices and programs were quite different.  I don't believe that the
	original asssumptions hold true any long.  If Symbolics has evidence
	that this optimization is worth the complexity, then I and a number of
	other people would be very interested in seeing it.

    Of course it depends a lot on the time cost of dealing with cdr-coding,
    on how much memory costs, on how much memory your program needs, and
    which program you're running, and how much of your data structure is
    lists versus non-lists, and how many references are to lists (do you
    make a whole lot of big lists that you rarely refer to, or the
    opposite), and so on.  There are other issues here that are really too
    complex to go into in detail.  No, I don't know of any explict attempts
    to do these measurements lately.

Memory prices are not the only justification for making list-structures
50% more compact (best case, of course).  More compact lists produce
much better paging performance.