Date:	Wed, 14 Jun 1995 10:37:55 -0400
From:	kagel AT quasar DOT bloomberg DOT com
To:	r DOT grunwald AT cowan DOT edu DOT au
Cc:	djgpp AT sun DOT soe DOT clarkson DOT edu
Subject:	Re: Malloc without malice 2
Reply-To:	kagel AT ts1 DOT bloomberg DOT com

   From: "Ron Grunwald" <RGRUNWAL AT wasp DOT cs DOT cowan DOT edu DOT au>
   Organization:  Edith Cowan University
   Date:          Wed, 14 Jun 1995 09:40:28 GMT+800
   Reply-To: r DOT grunwald AT cowan DOT edu DOT au

   Art S. Kagel wrote:

   > I have a sort program I ported to DJGPP which malloc() and free()s all
   > over the place and it has never failed.  I have sorted files of several
   > hundred thousand records which translates to over 1/2 million malloc()s
   > and matching free()s.

   Doing around 1/2 million function calls to malloc(), isn't that a bit
   inefficient, considering the enourmous execution thread the system has to
   follow to allocate a single block of memory?

   Using the stack might be a much faster method as you only need 3 assembly
   language instructions for the same task.

   Eg.

	push ebp 
	mov ebp,esp
	sub ebp,BLOCKSZ


   Regards, Ron.

In general, this might be good solution, however the program uses an iterative
version of the sort so a function call is made for each record.  At the very
least I would have to adjust the stack pointer.  But, even this would cause
problems as the allocations of data structures within the algorithm function
would become orphaned when the function returned and overwritten by subsequent
calls.  I know that I need to implement a cheaper memory manager than malloc
for this app, but, it flies now so the incentive is not there.

Note that for files large enough to worry about it the task is broken into temp
files containing, except for the last (or if dups deletion occurs), a fixed (or
at least a max.) number of records.  Once the first temp file is written and
its memory freed, malloc is not going to the OS for memory any longer so it is
pretty fast.

Thanks for giving thought.

-- 
Art S. Kagel, kagel AT ts1 DOT bloomberg DOT com

Variety is the soul of pleasure.  --  Aphra Behn

- Raw text -