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Re: [Lzip-bug] lzip memory & performance issue

From: Antonio Diaz Diaz
Subject: Re: [Lzip-bug] lzip memory & performance issue
Date: Sun, 27 Feb 2011 20:37:49 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i586; en-US; rv:1.7.11) Gecko/20050905

address@hidden wrote:
However, the lzip manual says:
  "Note that dictionary sizes are quantized. If the specified size does
not match one of the valid sizes, it will be rounded upwards."

What are the relevant sizes that the dictionary is quantized to? Could
lzip have been trying to use a much larger dictionary size when I
specified 256MiB?

As you can see here[1], dictionary sizes that are a power of two are coded exactly. So lzip uses exactly 256MiB when you specify 256MiB. For other values, lzip divides the space between any two powers of two in 16 intervals of equal size (wedges). For example, any value between 249MiB and 255MiB will be rounded upwards to 256MiB.
[1] http://www.nongnu.org/lzip/manual/lzip_manual.html#File-Format

Thanks for telling me about this. I'll try to explain it more clearly in the next version of the manual.


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