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Date: Mon, 6 Feb 2017 18:58:29 -0600 (CST)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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Cc: tiff@lists.maptools.org
Subject: Re: [Tiff] Qs about support for more than 2^16 IFDs and writing
 performance
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On Tue, 7 Feb 2017, Paavo Helde wrote:

>
> On 7.02.2017 2:04, Bob Friesenhahn wrote:
>>   The linear scan is perhaps not the
>> fastest algorithm but it should not take terribly long (much less than
>> a second) to scan 65535 entries.e e
>
> And if you multiply a second by 60,000, then you get many hours. Writing
> a TIFF file with 60,000 IFD-s will call TIFFLinkDirectory() 60,000 times.
>
> Note that such files typically do not fit in L3 cache and thus
> traversing them may be extremely slow. We are talking mostly of BigTiff
> format here.

This sounds reasonable.  We need a good test case for this (portable C 
source code) which be used to measure the performance impact and 
evaluate solutions.

Bob
-- 
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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