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https://issues.apache.org/jira/browse/LUCENE-9286?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17078075#comment-17078075
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Dawid Weiss commented on LUCENE-9286:
-------------------------------------
I love the patch and the idea, Bruno. But the cost of construction and
traversal have gone high up for me. On a slower-ish dell laptop I get the
following on master (same code as in that tiny repo before):
{code}
FST construction (of=0.8) 2s 299ms 9.4% 11s
TermEnum scan (of=0.8) 391ms 1.6% 14s
FST construction (of=1.0) 5s 24.0% 14s
TermEnum scan (of=1.0) 3s 938ms 16.1% 20s
{code}
whereas after the patch compilation and enumeration goes up to a whopping 35+
seconds!
{code}
FST construction (of=0.8) 2s 357ms 2.6% 13s
TermEnum scan (of=0.8) 457ms 0.5% 16s
FST construction (of=1.0) 37s 41.8% 16s
TermEnum scan (of=1.0) 35s 39.6% 54s
{code}
This is a bit strange, isn't it? I don't think I've changed anything regarding
fst parameters:
https://github.com/dweiss/lucene9286/commit/1fb899e018712e9637984d95937c50b4bc9ffa97#diff-32e7e4311056421eef9f3a87a4ec51f7R56-R66
I'm not sure where the difference comes from and why it's so slow -- I'll try
to get an execution profile later today.
> FST arc.copyOf clones BitTables and this can lead to excessive memory use
> -------------------------------------------------------------------------
>
> Key: LUCENE-9286
> URL: https://issues.apache.org/jira/browse/LUCENE-9286
> Project: Lucene - Core
> Issue Type: Bug
> Affects Versions: 8.5
> Reporter: Dawid Weiss
> Assignee: Bruno Roustant
> Priority: Major
> Attachments: screen-[1].png
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> I see a dramatic increase in the amount of memory required for construction
> of (arguably large) automata. It currently OOMs with 8GB of memory consumed
> for bit tables. I am pretty sure this didn't require so much memory before
> (the automaton is ~50MB after construction).
> Something bad happened in between. Thoughts, [~broustant], [~sokolov]?
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