RFR: 8288979: Improve CLDRConverter run time

[Roger Riggs]

On Wed, 22 Jun 2022 14:24:05 GMT, Daniel Jeliński <djelinski at openjdk.org> wrote:

> This PR improves the performance of deduplication done by ResourceBundleGenerator.
> 
> The original implementation compared every pair of values, requiring O(n^2) time. The new implementation uses a HashMap to find duplicates, trading off some extra memory consumption for O(n) computational complexity. In practice the time to generate jdk.localedata on my Linux VM files dropped from 14 to 8 seconds.
> 
> The resulting files (under build/support/gensrc/java.base and jdk.localedata) have different contents; map iteration order depends on the insertion order, and the insertion order of the new implementation is different from the original.
> The files generated before and after this change have the same size.

make/jdk/src/classes/build/tools/cldrconverter/ResourceBundleGenerator.java line 146:

> 144:             // generic reduction of duplicated values
> 145:             Map<String, Object> newMap = new HashMap<>(map);
> 146:             Map<BundleEntryValue, BundleEntryValue> dedup = new HashMap<>(map.size());

LinkedHashMap could be used to retain the iteration order.
Or TreeMap if some deterministic order was desirable.

make/jdk/src/classes/build/tools/cldrconverter/ResourceBundleGenerator.java line 157:

> 155:                             fmt = new Formatter();
> 156:                         }
> 157:                         String metaVal = oldEntry.metaKey();

The new instanceof pattern matching could be used avoid the cast below.

make/jdk/src/classes/build/tools/cldrconverter/ResourceBundleGenerator.java line 270:

> 268:                 if (value instanceof String s) {
> 269:                     return s.equals(entry.value);
> 270:                 } else if (!(entry.value instanceof String[])) {

Could be re-written to use instanceof pattern and save a cast.

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PR: https://git.openjdk.org/jdk/pull/9243