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Subject: 
Re: MPD file loading search order
Newsgroups: 
lugnet.cad.dev
Date: 
Wed, 26 Jul 2006 05:09:30 GMT
Viewed: 
2245 times
  
In lugnet.cad.dev, Lars C. Hassing wrote:
In lugnet.cad.dev, Travis Cobbs wrote:
However, I can tell
you what I do in LDView, so that you have an idea of how at least one
MPD-compatible program {does} work.

Thanks for your thorough explanation.
I'm happy to see that the functionality is the same as that of the L3 parser!

Wow, that's impressive.  I'm pretty sure it's accidental, too.  (Accidental on
my part; your L3P parser was obviously there first.)


Only one file is open at a time.
Subfiles of unused parts in an MPD will not be loaded.

LDView only has one file open at a time also (unless I'm mis-remembering my
implementation), since the actual loading of sub-models happens after the parent
model has been completely read into memory (during pass 2, the parsing pass).  I
never really thought about it before, but I believe that it also doesn't load
any subfiles of unused models in the MPD, since the only way a model gets loaded
is during the parsing of its parent model.


It was stated back in 2000 that files in an MPD are public:
http://news.lugnet.com/cad/dev/?n=4188&t=i&v=a

Scanning that thread, I'm not sure there was actual consensus on that point.
Don suggested that maybe the contents of the MPD should be scoped, but it seems
obvious that he didn't actually do that at the time.  Jacob said that since MPD
files represent a collection of files on a disk, it didn't make sense to have
two different versions of a subfile inside two MPD files in the same directory.
Steve seems to have agreed with Jacob, although he didn't say it in as many
words.  And, he seemed to state that he wasn't positive, but highly confident
that files in an MPD are public.  (Seems to state, because he answered an
either/or question with "no".  I believe he was saying "no" to the second
portion of the either/or, i.e. that they're private.)

That thread does mean that I need to go back and take another look at the MPD
spec.  Nowhere in the LDView source code tree does the word "nofile" appear. :-O
Seems like an oversite, although LDView will just spit out a bunch of warnings
if there's garbage data after a 0 NOFILE line in a file.

--Travis



Message has 1 Reply:
  Re: MPD file loading search order
 
(...) You're right, but Jacob invented the MPD, so I guess I just followed his wish, though I would have preferred the scoping. Also he suggests a way to get scoping anyway: "0 FILE house1/house1.dat" which nicely reflects the storage on the disk. (...) (18 years ago, 26-Jul-06, to lugnet.cad.dev)

Message is in Reply To:
  Re: MPD file loading search order
 
(...) Well, if you read all postings on MPD through the last seven years you should be able to piece the correct answer together :-) I believe the L3 parser (used in L3P, L3Lab and "ldglite -l3") reflects that information. > However, I can tell (...) (18 years ago, 25-Jul-06, to lugnet.cad.dev)

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