Re: Binary property list efficiency issue

• Subject: Re: Binary property list efficiency issue
• From: Steve Baxter <email@hidden>
• Date: Fri, 20 Jan 2006 11:18:20 +0000
• Delivered-to: email@hidden
• Delivered-to: email@hidden

You might want to look at Metakit:

http://www.equi4.com/metakit.html

It's pretty efficient for quite large amounts of data.

Cheers,

Steve.

On 20 Jan 2006, at 09:47, Laurence Harris wrote:

On 1/20/06 3:12 AM, Matt Gough didst favor us with:

On 20 Jan 2006, at 07:16, Laurence Harris wrote:

Here are some times I got in testing. Property list has a small
header which
is the same size for every list and a main array. All times are the
time
spent in CFPropertyListWriteToStream:

1,538 items:
binary 1.65
XML 0.317

8,365 items:
binary 63.58
XML 0.933

31,041 items:
binary 1499.033 secs
XML 3.583 secs

The XML times go up linearly. The binary times appear to be going up
exponentially. This makes the binary format completely unusable for
large
lists with its current implementation. I can't ask users to wait 25
minutes
while I save a file.

Larry,

This reminds me of a similar situation with Cocoa Archiving. I think
the Binary version is trying to only add each 'duplicated' value for
everything only once and then just inserting a reference to the
original each time a duplicate is encountered. The plain version is
obviously not allowed to do this. Hence as the list gets bigger, the
time to compare each item against all the others grows exponentially.

I believe this is what's happening. Seems like CFSet should use a more
efficient mechanism for handling this, though.

If you want to save space, I would suggest creating a text property
list into memory and then using zlib to compress that down. I suspect
that will be a lot quicker, if not maybe so small overall.

Hmm. Interesting. Plenty to think about here. Thanks to everyone for the
thoughts.

Larry

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