Memory, 2004 vs 2005, or else?

I have an Autolisp routine that creates from a blank drawing, very large
drawings. Under version 2004 and an older machine (Athalon 900mhz with 1.25
Gb Ram) under Windows 2000 Pro, it recently (and mostly successful) created
a 75 mb drawing. Yes, I was able to save it but frankly was not able to
close Autocad gracefully. FWIW my program reports in separate text file,
memory in use at certain program milestones and at program's end, 91% memory
was in use.



My point here is that the routine completed its run.



About this same time, I received in the mail version 2005 and I installed
that on the old machine hoping the new version would ease what looked like a
memory problem. I then decided to try that same task using 2005 but it
never completed more than 50% of the drawing before the following error
message appeared:



; warning: unwind skipped on exception

; error: Exception occurred: 0xE0000001



That and several other experiences suggested that I could be approaching
hardware limits so I built a new machine, this one with a Pentium P4, 3 Ghz,
and 1.5 Gb Ram. While building the new machine I also decided to modify my
lsp code with the objective of conserving memory, this by creating the
drawing in pieces, where I could later reassemble the entire drawing later.
To put it simply, while I deposit a certain count of entities I Wblock those
to Filename1.dwg (which naturally erases them from the current drawing) and
proceed. . deposit so many, Wblock to Filename2, and so forth. This way,
the current drawing under which the Lisp operates, can never get larger than
a certain amount - or so I figured.



Yesterday, I was excited as I tried the new code under 2005. I watched as
entities were laid down until my entity limit was reached (I set it to
10,000) and then disappear as Wblock did its thing. Then, more entities,
etc. However, despite my regular offloading I noted more and more disk
activity where at only 1/5 of completion the disk light was on constantly.
The drawing never finished beyond some 95% completion when that dreaded
error message appeared again.



I then installed 2004 (better get the sheriff after me) and tried the same
task. It finished! Yes, it took nearly 5 hours, and had the same heavy
disk activity as 2005 - but it completed the drawing. Yes, the final
drawing was comparatively small, some 7.5 Mbytes and I saved that drawing
"piece" and I believe I can reassemble the drawing for plot time when I need
to. My memory report at conclusion showed some 76% (x 1.5 = 1.14 Mbytes?)
of RAM in use.



I have several questions here. The main one is why so much disk activity
since I'm Wblocking my entities to disk in stages - in essence, offloading
drawn entities to other disk-based drawings?



After each Wblock operation should I also be doing a SAVE. Perhaps SAVE
does some special type of purging of the drawing database? How about a
formal PURGE following each Wblock?



As it stands, I create these entities from, not one, but a number of lists.
As I Wblock a set of entities, and to conserve memory, I setq that list to
NIL since it is no longer needed, then move on to the next list.



Is there anything else I can do along the way to stop this disk swapping and
use more of the RAM I bought?


Len Miller