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Posted to dev@lucene.apache.org by "Adrien Grand (JIRA)" <ji...@apache.org> on 2013/01/07 17:12:13 UTC
[jira] [Commented] (LUCENE-4643) PackedInts: convenience classes to
write blocks of packed ints
[ https://issues.apache.org/jira/browse/LUCENE-4643?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13545995#comment-13545995 ]
Adrien Grand commented on LUCENE-4643:
--------------------------------------
I made some tests with my compressed TermVectorsFormat and the problem is that it sometimes wastes space. For example if all values from a block are between -1 and 6, the first patch would require 3 bits whereas the 2nd one + zig-zag encoding a level above would require 4 bits per value so I think I should rather commit the first patch?
> PackedInts: convenience classes to write blocks of packed ints
> --------------------------------------------------------------
>
> Key: LUCENE-4643
> URL: https://issues.apache.org/jira/browse/LUCENE-4643
> Project: Lucene - Core
> Issue Type: Bug
> Reporter: Adrien Grand
> Assignee: Adrien Grand
> Priority: Minor
> Attachments: LUCENE-4643.patch, LUCENE-4643.patch
>
>
> It is often useful to divide a packed stream into fixed blocks which are all compressed independently:
> * if your sequence of ints is very large, you won't have to buffer everything into memory to compute the required number of bits per value,
> * the compression ratio will be better in case of rare extreme values.
> The only drawback compared to the original PackedInts API is that the stream cannot be directly used to deserialize a random-access PackedInts.Reader (but for sequential access, this is just fine).
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