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From "Paul Elschot (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (LUCENE-1410) PFOR implementation
Date Wed, 22 Dec 2010 18:14:02 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12974303#action_12974303
] 

Paul Elschot edited comment on LUCENE-1410 at 12/22/10 1:13 PM:
----------------------------------------------------------------

bq. ... is it possible to encode # of exception bytes in header?

In the first implementation the start index of the exception chain is in the header (5 or
6 bits iirc). In the second implementation (by Hoa Yan) there is no exception chain, so the
number of exceptions must somehow be encoded in the header.
That means encoding the # exception bytes in the header would be easier in the second implementation,
but it is also possible in the first one.

I would expect that a few bits for the number of encoded integers would also be added in the
header (think 32, 64, 128...).
The number of frame bits takes 5 bits.
That means that there are about 2 bytes unused in the header now, and I'd expect 1 byte to
be enough to encode the number of bytes for the exceptions. For example a bad case in the
first implementation of 10 exceptions of 4 bytes means 40 bytes data, that fits in 6 bits,
the same
bad case in the second implementation would also need to store the indexes of the exceptions
in 10*5 bits,  for a total of  about 48 bytes that can be still be encoded in 6 bits. However,
I don't know what the worst case # exceptions is. (This gets into vsencoding...)

For the moment I'll just leave this unchanged and get the tests working on the current first
implementation.

      was (Author: paul.elschot@xs4all.nl):
    bq. ... is it possible to encode # of exception bytes in header?

In the first implementation the start index of the exception chain is in the header (5 or
6 bits iirc). In the second implementation (by Hoa Yan) there is no exception chain, so the
number of exceptions must somehow be encoded in the header.
That means encoding the # exception bytes in the header would be easier in the second implementation,
but it is also possible in the first one.

I would expect that a few bits for the number of encoded integers would also be added in the
header (think 32, 64, 128...).
The number of frame bits takes 5 bits.
That means that there are about 2 bytes unused in the header now, and I'd expect 1 byte to
be enough to encode the number of bytes for the exceptions. For example a bad case in the
first implementation of 10 exceptions of 4 bytes means 40 bytes data, that fits in 6 bits,
the same
bad case in the second implementation would also need to store the indexes of the exceptions
in 10*5 bits, totalling 90 bytes that can be
encoded in 7 bits. However, I don't know what the worst case # exceptions is. (This gets into
vsencoding...)

For the moment I'll just leave this unchanged and get the tests working on the current first
implementation.
  
> PFOR implementation
> -------------------
>
>                 Key: LUCENE-1410
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1410
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: Index
>            Reporter: Paul Elschot
>            Priority: Minor
>             Fix For: Bulk Postings branch
>
>         Attachments: autogen.tgz, for-summary.txt, LUCENE-1410-codecs.tar.bz2, LUCENE-1410.patch,
LUCENE-1410.patch, LUCENE-1410.patch, LUCENE-1410.patch, LUCENE-1410b.patch, LUCENE-1410c.patch,
LUCENE-1410d.patch, LUCENE-1410e.patch, TermQueryTests.tgz, TestPFor2.java, TestPFor2.java,
TestPFor2.java
>
>   Original Estimate: 21840h
>  Remaining Estimate: 21840h
>
> Implementation of Patched Frame of Reference.

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