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https://issues.apache.org/jira/browse/LUCENE-4098?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Adrien Grand updated LUCENE-4098:
---------------------------------
Attachment: LUCENE-4098.patch
Here is the patch for the proposed modifications. All {{Mutable}}
implementations have a new efficient {{fill}} method and Packed64SingleBlock*
classes also have efficient bulk get and set.
For example, the execution time of the following (unrealistic) microbenchmark
is more than twice better with the patch applied on my computer thanks to the
use of {{PackedInts.copy}} instead of naive copy (see
{{GrowableWriter#ensureCapacity}}).
{code}
for (int k = 0; k < 50; ++k) {
long start = System.nanoTime();
GrowableWriter wrt = new GrowableWriter(1, 1 << 22, PackedInts.DEFAULT);
for (int i = 0; i < 1 << 22; ++i) {
wrt.set(i,i);
}
long end = System.nanoTime();
System.out.println((end - start) / 1000000);
long sum = 0;
for (int i = 0; i < wrt.size(); ++i) {
sum += wrt.get(i);
}
System.out.println(sum);
}
{code}
> Efficient bulk operations for packed integer arrays
> ---------------------------------------------------
>
> Key: LUCENE-4098
> URL: https://issues.apache.org/jira/browse/LUCENE-4098
> Project: Lucene - Java
> Issue Type: Improvement
> Components: core/other
> Reporter: Adrien Grand
> Priority: Minor
> Fix For: 4.1
>
> Attachments: LUCENE-4098.patch
>
>
> There are some places in Lucene code that {iterate over,set} ranges of values
> of a packed integer array. Because bit-packing implementations (Packed*) tend
> be slower than direct implementations, this can take a lot of time.
> For example, under some scenarii, GrowableWriter can take most of its
> (averaged) {{set}} time in resizing operations.
> However, some bit-packing schemes, such as the one that is used by
> {{Packed64SingleBlock*}}, allow to implement efficient bulk operations such
> as get/set/fill. Implementing these bulk operations in
> {{PackedInts.{Reader,Mutable}}} and using them across other components
> instead of their single-value counterpart could help improve performance.
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