NetNews Usenet Archive 1993 #1/NN_1993_1.iso/spool/comp/sys/mac/programm/20983

Internet Message Format | 1993-01-08 | 1.7 KB

Path: sparky!uunet!mcsun!sun4nl!tuegate.tue.nl!svin09!wsinpa04!wstomv
From: [e-mail] (Tom Verhoeff)
Newsgroups: comp.sys.mac.programmer
Subject: Why is new(p) so slow in THINK Pascal?
Keywords: THINK Pascal, dynamic variables
Message-ID: <[e-mail]>
Date: 8 Jan 93 11:58:05 GMT
Sender: [e-mail]
Reply-To: [e-mail]
Lines: 25

In order to compare some sorting procedures for linked lists (implemented
in THINK Pascal) I applied them to random lists of varying lengths.
It turns out that the procedure new(p), which allocates storage for
a dynamic variable pointed to by p, is extremely slow.  Does anyone
know why?  New-ing a thousand items takes a noticeable time, new-ing
10,000 items takes minutes (on my lowly SE/30).

I did call MaxApplZone at the very beginning of my program.  I also
tried various numbers of calls to MoreMasters, without avail.
I presume that dynamic variables in THINK Pascal are stored in
non-relocatable blocks (where can I find that information; in my 4.0
manuals I couldn't find a clue), and therefore MoreMasters would not
be useful anyway.

My practical solution is to create a FreeList of free dynamic variables
and prime it at the beginning with a sufficient number items.
Instead of new and dispose I then use NewElement and DisposeElement
defined in terms of the FreeList.  Now it works like a train, except...
that priming is still incredibly slow (fortunately to be done only once).

    Tom
--
INTERNET: [e-mail]  /    Eindhoven University of Technology
VOICE: [phone]      /    Dept of Mathematics & Computing Science
FAX: [phone]       /    PO Box 513, NL-5600 MB Eindhoven, Netherlands