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ICU 53 collation v2 work log

The "collation v2" reimplementation went into ICU 53 (both C++ & Java). The following is a raw copy of the relevant parts of a "Collation v2 TODO" doc with tasks, questions, notes, and decisions.

After ICU 53, the collation code is again maintained as usual, with further incremental enhancements and bug fixes.

UTS #10=UCA spec: Read the latest draft at

UTS #10 bugs: Submit report at

UTS #35=LDML collation: Read the latest draft at

ICU collation tickets

CLDR collation tickets

“Collation subcommittee”: Mark Davis, Yoshito Umaoka, Peter Edberg, Vladimir Weinstein

mark, yoshito, pedberg, weiv







Q: Is v2 fast enough?

Q: Do we need a compare() Latin-1 fastpath like in v1?

  • Done 2013aug: Apparently needed; Yoshito’s initial benchmarking suggested 60% slower Latin-1 without the fastpath. Added new fastpath with small memory-mapped data, for both UTF-16 and UTF-8, and supporting more characters and more collator attributes.

  • If so, for both UTF-16 and UTF-8?

    • Yoshito: UTF-8 is higher priority in IBM

  • Performance vs. code bloat & complexity & heap memory (over 3kB per Collator instance) & slower first use and setAttribute()

    • Might be able to reduce the size and store it with the binary data and not modify it in setAttribute(), might extend it to Latin-A for all of French and some more languages, see details later in this doc

Q: Potential for other performance improvements in the all-Unicode compare() functions??

  • Maybe even enough to not need a Latin-1 fastpath?

  • See details later in this doc

Compare v1 vs. v2 performance “Collation performance tests for ICU4C”

Q: Take code from existing collperf test?

User operations to test:

  • sort list of strings

  • search for a string in a sorted list

    • Yoshito: My understanding is that the scenario used in the existing test case is not matching our main customer’s interest. Especially, sorting performance test with qsort is far from the customer’s usage scenario. - They use a variation of radix sort based on incremental access of collation key value - therefore, their implementation always produce necessary length of collation key for each, not depending on ucol_strcoll. It can still measure ucol_strcoll’s performance, but with unnecessary noise (qsort or binary search algorithm part).

Collator API to use:

  • compare(UTF-16 UnicodeString (with length))

  • compare(UTF-8 with length)

  • Q: Do we need to benchmark nextSortkeyPart(UTF-8 UCharIterator) with a radix sort?

    • Yoshito: I don’t think we need radix sort implementation. We just need to understand how nextSortKeyPart is invoked and measure “pure” peformance of the function.

Languages: (some may have the same collation order, but the test strings should mostly be in the tested language, giving a different mix of ASCII vs. other Latin etc.)

  • en · de · ru · th · ja · zh-u-co-pinyin

Collator settings to use (several settings, to get a better idea for common and desirable use cases, and to help justify the reimplementation):

  • language defaults

  • ignore case: strength=2

  • ignore accents: strength=1 & caseLevel=on

  • ignore punctuation: strength=4 & alternate=shifted & normalization=on

    • normalization guarantees correct results, as in JavaScript i18n, and “ignore punctuation” is a desirable use case

Proposed combinations, rather than the cross-product of language x settings. (Still should test both UTF-8 & UTF-16.)

  • locale=en, default settings; English strings

  • locale=de@collation=phonebook, ignore case: strength=2; German strings

  • locale=fr, ignore accents: strength=1 & caseLevel=on; French strings

  • locale=ru, ignore punctuation: strength=4 & alternate=shifted; Russian strings

  • locale=th, normalization=on & alternate=shifted; Thai strings

  • locale=th, normalization=on & alternate=shifted; English strings

  • locale=ja, strength=5 (full JIS X 4061); Japanese strings

  • locale=ja, strength=5 (full JIS X 4061); English strings

  • locale=zh@collation=pinyin; Chinese strings

  • locale=zh@collation=pinyin; English strings

Markus 2013nov08: I did implement a new Latin fastpath [...]. It covers a larger set of Latin characters than before, so it should bail out to the normal path less often. We could include an eastern European language like Polish to see if there is a noticeable difference.

July 23, 2013 update: Yoshito ran the existing collation performance regression test suites with a simple hack - setting an instance of root collator created by CollationRoot::createCollator(status) to Collator* UCollator.delegate. UCollator.delegate is designed for collation plug-in, but it would be sufficient enough to see the performance trend with the new code. Many test cases are within +/- 5% range, except following two cases:

  • Key Gen (ucol_getSortKey performance) dropped about 20%-40%

  • Binary Search (ucol_strcoll) dropped about 60% for Latin data (equal or better for other scripts)

The latter issue found in Latin is likely caused by Latin 1 optimization and I think this is already in plan. However, key generation performance drop might need to be investigated.


Yoshito & Markus

Obsolete 2013oct: So far, v2 code is tested via

  • intltest collate/UCAConformanceTest (currently tests only v2, with UCA 6.3/CLDR 24 root data; the v1 code still uses UCA 6.2 which would fail with the new conformance test files)

  • intltest collate/CollationTest, v2-specific and mostly data-driven

Done 2013oct: Eventually, all existing tests will use the new code.

Obsolete 2013oct (replaced v1 code with v2 code, fixing tests) – Q: How, and how early, can/should we use v2 code in more of the tests?

  • Idea: When the Collator runtime code is complete, return a v2 Collator instance whenever the test code does not build or load a rule-tailored collator (root, de-u-co-standard, etc. -> getTailoredSet()->isEmpty()).

  • Probably best to do this under an #ifdef because there will be some failures.

  • Probably need to make some test code changes to cope with implementation differences. For example, casting to RuleBasedCollator will fail (or produce a bad pointer) as long as v2 is implemented as RBC2. Use more virtual/internal Collator base class methods, maybe use dynamic_cast and check for NULL. Maybe move some tests from C to C++ to make such changes workable.

  • Idea: Return new Collator when building from rules.

Add tests (data-driven or otherwise) to confirm v1 bugs and to verify that they are fixed in v2.

  • See this query of ICU collation tickets.

  • Done 2013jun: Use the Trac ticket keyword “fixed-collv2” to indicate that the collv2 branch has a test for the bug (and it passes).

Q: There are many bug tickets for v1. What is a good way to verify that v1 indeed fails them and v2 passes?

  • Idea: Does it make sense to run the data-driven CollationTest on v1 collator instances as well? Print warnings for failures with v1??

  • Or else write specific test code to let v1 fail and later verify that v2 passes as we switch the implementation? It would be nice to be able to use the data-driven test framework.

  • Maybe some temporary syntax in the data-driven test data file that indicates using a v1 Collator??

  • Idea: Write test code using the regular public API, use #ifdef from previous “Q” to switch between v1 & v2. Affected tests should fail with v1 and pass with v2.

  • Better idea: Set environment variable (getenv()) COLLTESTV1=1 to switch the data-driven tests to the existing public (v1) Collator API (as much as possible). Add test cases, with the v1-bug-ticket numbers in comments. Test that these cases fail with v1 & work with v2.

    • Note: Some test code cannot work with v1; for example, v1 nextSortKeyPart() will return different sort keys than getSortKey(), by design.

    • FYI: When we eventually merge the collv2 work into the trunk, the code for testing the existing Collator API will remain, and the one using the v2-specific class names will be removed.

  • Simpler: Verify bugs with the online collation demo, add tests in v2 data-driven test code.

Obsolete 2013oct: Note: collate/CollationTest will eventually need to use the public API anyway. An #ifdef could help do that early.

Obsolete 2013oct: Idea: Temporarily, as long as v2 is missing some functionality, a v2 instance could also have a pointer to a v1 version. For missing functionality it would call the v1 function.

Done 2013nov20: r34675 “delete low-ROI tests that depended on the old rule parser and other deleted internals: cmsccoll/TestCollations, cmsccoll/RamsRulesTest, cmsccoll/TestRedundantRules (collationtest.txt), cmsccoll/TestExpansionSyntax (collationtest.txt), much of cmsccoll/TestVariableTopSetting (replaced by spot checks), citertst/TestCEs” see “collv2 test review

try to simplify collate/CollationTest

  • Postponed: try to share code with existing framework; for example, prettify(CollationKey)

  • Done 2012nov26: try to work with a root collator rather than building a new base

  • Done 2012nov26: try to replace rawbase tests with raw tailorings or even rules

  • Postponed: move base data builder to toolutil?

  • Postponed: consider: DataDrivenCollatorTest also did this:

    • tested offsets (via IntlTestCollator?)

    • on each new Collator, did cloneBinary() and RBC(binary) and used both the original and the clone for testing

Done 2012nov23: test cloneBinary(): after construct(bin) cloneBinary() again, check same binary, construct(bin2), check equal collator (equal also to original), usable without crash

Done 2012nov22: collationtest.txt: reorder Zzzz Grek –> Han<Omega<FFFD<FFFF

Done 2012nov26: CollationTest: test string comparisons with NFD versions of strings, too

Done 2013dec20: valgrind and/or memory sanitizer

Collator runtime


Done 2012nov15: Finish compare(UTF-8)

Done 2013mar01: Implement getTailoredSet, getContractions() etc.

  • Iterate data structure, not re-parse rules

  • Done 2012nov16: Read all related API docs

  • Done 2012nov16: Q: Results for root/no tailoring rules? Fallbacks to root? Prefixes as contractions?!

Done: attributes: variableTop and/or maxVariable

  • Done 2012nov16: sent email to Peter “ICU collation: variableTop, maxVariable, modifier letters” asking about usage & concerns

  • Done 2012nov29: Peter replied that he has no concerns about replacing variableTop with maxVariable and pinning the variableTop values.

Done 2013sep24: internalGetShortDefinitionString()

Done 2013jul11: getMaxExpansion()

  • Done 2012nov16: sent email to icu-core “can we deprecate Collator::getMaxExpansion()?”

  • Done 2012nov28: deprecate RuleBasedCollator::getMaxExpansion()

  • Done 2013jul11: Implement in RBC, with mutex & lazy init for the data. Probably simplest to use a UHashtable. Pass that UHashtable into the CollationElementIterator constructor so that its getMaxExpansion() need not synchronize.

Done 2013feb: clone()

Obsolete 2013jul22: Normalization=on  (paper note 20130212)

  • Decompose U+0344 as well; and

    • Maybe not; see unicode list discussion 2013apr02 “FCD and Collation”, and

    • Thoughts 2013apr12:

      • If we do not add overlap contractions, then we have the ICU-documented limitation of decomposition mappings vs. contractions, for U+0344 as well as other composites (e.g., Danish aa vs. ä).

      • If we do add overlap contractions, then FCD text sorts like NFD text, but we change the sorting behavior of NFD text in some cases.

      • There is a theoretically unlimited number of overlap contractions for the Tibetan composite vowels, so we cannot “fix” them completely without decomposing them.

      • Decision 2013jul22: Document as in and in the email 2013apr02 “FCD and Collation” discussion

  • No need to decompose the problematic characters unless they are adjacent to ccc!=0

    • Decision 2013jul22: Untrue. Need to decompose Tibetan composite vowels even if not adjacent to ccc!=0 so that contractions with one of their pieces work. For example, for contraction x+0F72 we need to see the decomposition of <x, 0F73>.

Done 2013may: Put from-rules constructor into the parser file, to reduce dependencies

Postponed: Revisit root collator unsafeBackwardSet: Serialize whole set (consistent with UCA version, larger data, bound to UCD version, genuca bootstrapping would want FCD data from vs. only contractions (consistent with CollationFCD & normalization, slow runtime enumeration of FCD-unsafe characters, maybe fastpath in Normalizer2Impl?)  (paper note 20121228)

  • Done 2013dec11: optimize runtime enumeration of FCD-unsafe chars

Done 2013sep20: digits unsafe because of numeric collation?!

  • Seems unnecessary because the result should still be the same after an identical prefix with some of the digits.

  • Confirmed: However, we could get different results if there are more than 254 digits with some in the identical prefix.

    • Simpler: Test “11b” < “101a”

  • If needed: omit from binary, like normalization-unsafe chars.

  • Done: Consider treating them as unsafe only in code, not in the UnicodeSet, and only test if numeric=on.

    • inline CollationData.isUnsafeBackward(UChar32 c, UBool numeric /* spell like in CollationIterator */) const

    • if(unsafeBackwardSet->contains(c)) { return TRUE; }

    • if(!numeric) { return FALSE; }

    • if(c < 0x660) { return 0x30 <= c && c <= 0x39; }

    • return hasSpecialTag(getCE32(c), DIGIT_TAG);

Done 2013dec15: Implement “ICU API proposal: Collator variableTop -> maxVariable”


  • Done 2014feb21:

  • callcoll/TestVariableTop

  • “digit” withdrawn, only four valid values space, punct, symbol, currency (+default)

  • allow many CEs for variableTop as long as there is exactly one primary CE

  • consider changing the proposed API to adding a new UColAttribute and 4 new UColAttributeValue constants.

    • pro:

      • use setAttribute() etc.

      • avoid adding another setting that does not use setAttribute() [currently variableTop & reorder code] –> setting from locale keywords

      • if & when we want to write a BCP 47 settings string, we can easily use the explicitlySetAttributes

      • does not even look like all UColReorderCode values can be set (but most of them can)

    • con:

      • hardly better than current proposal?

      • adds 1+4=5 constants rather than 2 methods

      • harder to add digits if & when we might want to

      • adds to UColAttributeValue enum with few valid values per attribute, shares only “off”

      • there is no setAttribute() in Java, would have to invent something different there

Postponed: add RuleBasedCollator constructor with UParseError

Done 2013sep20: operator==()

Done 2013sep22: hashCode()

Done 2013sep23: getVersion()

Done 2013sep23: getLocale()

Done 2013sep23: getRules()

Done 2013sep22: cloneRuleData()

Done 2013sep22: cloneBinary()

Done 2013sep25: merge ^/icu/trunk into branch

  • done r34474: merge, and resolve conflicts

  • done r34484: make it work with new UInitOnce

  • done r34486: update for UCD 6.3 & UCA 6.3 (new FractionalUCA.txt?)

  • done r34485: adjust RBC for tblcoll.h

Done 2013oct30: propose const cloneBinary() etc., ticket 10428, done on collv2

  • sent proposal 2013oct07, approved:2013-10-30

Done 2013oct07: propose that the loader does not auto-build from rules any more when the binary is missing or has the wrong UCA version

  • old code set U_DIFFERENT_UCA_VERSION when appropriate (weakened from U_COLLATOR_VERSION_MISMATCH), with fallback to building from rules

  • dependencies!

  • someone trying to reduce data file sizes should omit the rule strings, not the binaries

  • sent to icu-core on 2013oct07, no replies

  • done on collv2, reminder TODOs still in ucol_res.cpp

Done 2013dec20: should the rule UnicodeString be bogus/NULL if it was omitted from the data?

  • Done 2013dec20: test in v1 (either write test program, or temporarily change “Sequence” in ucol_open_internal())

  • v1 ucol_getRules() has special code to return “” instead of NULL

  • A bogus Locale returns “” as well.

  • Keep returning “”, to avoid breaking callers.

  • Postponed: We should document that “” might mean that the rules are not available.

can we delete code in #if BOYER_MOORE ? (maybe just leave it but don’t try to make it work?)

Done 2013oct11: can we delete code in #ifdef U_USE_COLLATION_OBSOLETE_2_6 ? Collator::createInstance(locale, version, UErrorCode)

Done 2013oct11: can we delete various ucol.h @internal API?

  • ucol_equals() – moved to internal header, to avoid more work rewriting test code

  • ucol_getUnsafeSet() – keep

  • ucol_forgetUCA() – deleted

  • ucol_prepareShortStringOpen() – keep

  • sent proposal 2013oct07 –

Done 2013oct11: other tblcoll.h internals

  • setUCollator(locale): ignore; construct Tailoring outside, then construct RBC with that

  • getUCollator(): return cast(this)

  • virtual void setLocales(const Locale& requestedLocale, const Locale& validLocale, const Locale& actualLocale)

    • and ucol_setReqValidLocales()

    • It seems like the Collator (or its tailoring) should have an immutable actualLocale.

    • At most we should want to set the validLocale.

    • Asked 20130926 if we can drop support for the ULOC_REQUESTED_LOCALE

      • ures_getLocaleByType() always returns NULL, others set error

      • propose to set error; alternative maybe return valid locale?

      • Peter says ok to returning valid locale in ICU 53

      • For later:

Done 2013oct11: move the validLocale from the tailoring to rbc; add requestedLocale??

Done 2013oct20: rethink collation fast latin builder vs. runtime vs. u-umlaut contraction vs. finding difference at ‘u’ and returning rather than bailing out for the contraction (easy: just write an empty contraction list so that the runtime inspects the next character)

Done 2013nov08: clean up ucaconf.cpp test, try to resolve its pre-existing TODOs about v1 bugs

Done 2013dec19: (do this last) clean up warnings in test code, especially unused functions

Done 2013nov22: swap the new data structure (needed for Java port)

  • maybe move the swapper to toolutils?

Done 2013dec12: addContractions(cp, set) @internal  (paper note 20130305)

  • Adds contractions that start with cp to the set.

  • Ignores prefixes. Returns the number of items added.


  • Check tailorings for whether they set canonically equivalent strings to the same CEs. Japanese?

  • Maybe build this into the Builder, maybe with callbacks for informational output. Active in genrb, ignored at runtime.

  • Check tailorings for whether they make differences that are already the case, e.g., &c<<<C.


Done 2013dec20: check that all new code is inside #if !UCONFIG_NO_COLLATION

Done 2013dec20: adjust file comments saying back to C++ and replacing what old files

Done 2013nov09: remove any register-cleanup enum constants? UCLN_I18N_UCOL_RES? UCLN_I18N_UCOL_BLD?

Postponed: propose as public API the C<->C++ converters toUCollator(), fromUCollator(), toUCollationElements(), ...

Done 2013dec19: review tools/dumpce

  • Deleted 2013dec19.

  • Sent email to icu-core 20131011 asking whether we can remove it; Vladimir & Peter say yes.

  • No one seems to be using it.

  • It was not built via the tools/Makefile, nor via the MSVC allinone.sln. It had .dsp and .dsw files from a very old Visual Studio version.

  • Would need work:

    • Several of its core functions use the old implementation's internal rule parser, which is gone.

    • They would take some thought and work to replace; it would be better to work with getTailoredSet() and such. (In particular, one of the more useful genrb options removes the collation rule strings, and a tool like this should be able to work with the binary data.)

    • It would be better to get and print 64-bit CEs.

    • The tool does not handle multiple tailorings, or collation keywords/default etc.

Done 2013nov26: clean up genuca2.cpp

Done 2014feb24: after port to Java (when we do not need to generate data for the old version any more), move genuca2.cpp to tools/genuca

Done 2014feb25: after port to Java, merge into trunk; note data sizes before & after


Nothing to do (just keep as is in C API): Add UTRACE_... calls back into the runtime code.

  • Is this still used? -- 2013-sep: Yoshito says yes

  • Only in C API? – yes

Ideas for Fast Latin

  • Done 2013aug30 -- also included 2000..203F, FFFE, FFFF: See v2 design doc: Might extend the fastpath to U+017F, extend it to quaternary weights and handle alternate=shifted, and reduce it to 2 bytes per level.  (paper notes 20120909 & 20130110 & 20130112)

  • Done 2013aug30 -- made it 16b per char, based on some of the ideas here, with code complications for decoding (two types of expansions, two lengths of primary bit fields/two mini CE formats)

    • 32b per char? (about 1.6kB for up to U+017F)

    • Recode primaries to 7b each, maybe bail out if first CE is pri ignorable

      • 26 a-z, 48 Z/P/S, few more? (there are more even in Latin-1/A)

      • bail out if primary outside special groups+Latn (that is, >=Grek)

      • Bail out = 1

    • Maybe don’t go into fast-Latin if specials+Latn reordered relative to each other

    • Recode secondaries to few bits (keep WF2), few per primary, then sec CEs

      • First CE: completely ignorable or primary CE; Danish: up to 4 after common (0..4 if 0=common) → 3b?

      • Second CE can be secondary CE:

        • Latin-1: 88, 8A, 8E, 92, 96, 9A, 9E, A0

        • Latin-A: 8C, 90, 98, 9C, A2, A4, B2, FB 4C

        • 5b: 0=ignorable, 1=common, 2..5 for primary CEs, 6..31 for secondary CEs

        • Or 7b for both CEs, 5 values * 25 values, use tiny table

    • Case: 2x2b, or combined with tertiary

    • Tertiary: Bail out of fast Latn if no difference after secondary? Bail out if ter CE; else few per pri+sec (2 or 3b)

      • Maybe 3 case values & 5 ter values = 4b (case * 3 + ter), 0xf=uppercase with ter=5, use tiny table; Swedish: up to 4 after common (0..5 if 0=ignorable, 5 for uppercase AA)

      • Might not need case bits for second CE (except for &T<<<Þ/H), maybe just 2b ter

      • Second CE: Use value 0 for common; ter ignorable only if sec ignorable (all-zero fast-Latin value)

    • Simple, no tiny tables, always use 0=ignorable:

      • pri 7+7

      • sec 3+5

      • case 2+2

      • ter 3+3

    • Variable: Dynamic, bail out if two pri weights are not both var/non-var

    • Might bail out for sec/ter weights below common; might bail out of only sec/ter level, so that we can still compare on primary level.

    • Contraction (use high or low pri values): Top byte zero, then 5b a-z 5b A-Z or even assume uppercase of first; index to triple of default/lower/upper (need lists of up to 20 contraction suffix characters)

    • Might store in binary except “search”

    • Flag in data for fast Latin data same as in root, don’t duplicate it

Ideas for regular compare()

-- without CE buffers (hopefully speeds up primary level), with fast “equals” detection and level skipping (complicates primary level but short-circuits lower levels)

  • Count how many comparisons are decided on which level; and how many in identical-prefix comparison (U_DEBUG)

  • Withdrawn 2013jul02 (removing CE buffers) because it simplified the code significantly to have the CollationIterator have and build the whole CE buffer. -- For example, if 90+% of string comparisons are decided on a primary level, then we might remove the compare() method’s CE buffers. This might speed up primary-level comparison but we would have to re-fetch the CEs, either for every level, or just once (after level 1 compared equal) and buffer them then.

  • Some way for “equal” to be found without comparing each level separately, especially if we don’t buffer CEs, or at least short-circuit some of the lower levels? Seems like comparisons are usually primary different or equal.

  • Note: The identical-prefix code finds identical strings. It might make fast “equal” unnecessary, or vice versa.

  • Maybe compare whole CEs first, then primaries, then lower32s masked for settings, note if primary equal but not all equal, don’t buffer CEs.

  • Idea: Compare primaries and collect lower32Diffs=or-all(xor(pairs of lower32)). Maybe track leftVariable (init 0, set to 1 if multiple) and compareVariable (true if multiple, or right variable != leftVariable).

    • We could do this with or without CE buffering.

    • Most useful if good percentage of comparisons are decided on lower than secondary level, because we could short-circuit any work for intermediate levels.

    • If “equal” gets fast enough, then maybe we could remove the identical-prefix code??

    • Problem: Collecting/xor’ing of lower32 bits of primary ignorable CEs. Maybe set lower32Diffs=0xffffffff if any of those occur??

  • If primary equal, then:

    • If strength>=sec && lower32Diffs>>16 != 0: Iter & compare sec, must be !=equal. For backwards, go forward and collect in UnicodeString so that we don’t iter back into identical prefix; or maybe that’s harmless.

    • If caseLevel==on && lower32Diffs&case: Iter & compare case, may be equal depending on when we ignore case bits.

    • If str>=ter && lower32Diffs&terMask (can include case): Iter & compare ter, must be != equal.

    • If str>=quat && (lower32Diffs&quat || anyVariable/compareVariable): Iter & compare quat

    • Usually, iterates only once (primary diff) or twice. Does not inspect sec weights etc. at all if known no diffs there.

    • TODO: Need a good way to reset the iterators, preserving the identical prefix offset. (iter.resetToOriginalPos())

Done 2013jun25: Crazy idea: Redo specials

  • Use impossible case bits as specials flag: isSpecialCE32(ce32) { (ce32 & 0xc0) == 0xc0; }  // slower?! -- might be at least as fast in Java where unassigned comparisons are not built in

  • ce32 == 0xc0 for fallback: CASE_MASK, SPECIAL_CASE, MIN_SPECIAL_CE32

  • all indexes could have the same number of bits, shared setter/getter

  • more bits per special (20 → 26)

    • might especially help digits with currently only a 16-bit index

    • might put index into 20 upper bits, then tag, then 2 specials flags, then 6 bits for contraction flags, expansion lengths (no more escape for long expansions), digit values

  • more tags

    • use only 1 for Latin expansion, not 6

    • use a separate tag for U+0000

  • primaries can use byte FF

  • Done 2013jun16: more named constants, for contraction optimization flags, for max contr/exp/prefix index

  • measure perf of this specials test vs. <=0xff000000 (UCAConformanceTest did not get slower, looks very slightly faster)



Done Q: ticket #9104 “does CollationElementIterator (need to) support switching next/previous direction on the fly?”

  • Deprecated the support for switching direction without reset() etc. in ICU4J

Done 2013jul11: Reimplement CollationElementIterator API via (internal) v2 CollationIterator; some 64-bit CEs map to two 32-bit CEs (second is continuation)

  • 2012nov16: sent email to icu-core “who uses CollationElementIterator?”

  • can we deprecate it as public API??

    • no, it’s public even in the JDK

String search


Done 2012dec19: Retract Boyer-Moore string search code and its test cases (ticket #9573)

  • TODO: Confirm that this is the only use of getMaxExpansion()!

Postponed: Consider changing string search to using the internal v2 CollationIterator directly, or maybe with some wrapper code -- working with 64-bit CEs.

  • This could be done after most of the other work

  • See question above about deprecating the public CollationElementIterator API

  • Alternative 1: Ideas for new, more convenient iterator API (maybe not public API)

  • Alternative 2: Mark has ideas for a new version of string search that does an initial search in character space (get him to write them down...)

Mark’s UCA tools & FractionalUCA.txt


UCA/LDML spec changes

  • Done in UCA 6.3: U+FFFD with third-highest primary weight

Done 2012nov28: Add CLDR root collation data files into CLDR/collation/uca/ (CldrBug:5386)

Done 2012dec: Fix bugs in Mark’s code

  • Fix/new contraction matching code & data structure & builder

Done 2013jan: Improve FractionalUCA.txt

  • Compressible data: Dense ranges of primary order, optimized secondaries & tertiaries (merge secondaries into primary CEs & distribute per-primary secondaries/tertiaries), etc.

  • Fix bugs: Add tailoring gaps for secondary & tertiary weights

  • Complete data in the .txt file, avoid circular dependency with new UCD: Use case bits from UCA decomps.txt, list Unified_Ideograph, simpler script order data, etc.

Postponed: Make UCARules.txt work with builder that forbids tailoring primary-after ignorables

  • UCAConformanceTest::TestRulesNonIgnorable

  • Try to reset to special reordering groups as appropriate, then after [last regular]


  • 2013nov13: Sent email to “subcommittee” with subject “UCA_Rules.txt: remove? or fix how far?”

    • Client seems to be using the UCA_Rules to find equivalences, not order. Probably does not care about passing the UCAConformanceTest.

Postponed: If we only cared about compare() speed, not sort key lengths, then we would not have any 1-byte primary weights. We would free up dozens of lead bytes. (paper note 20131110)

  • We could just have a larger gap after each a-z for 2-byte tailored primaries.

  • Consider changing Nd (0-9) to two-byte primary weights. That would free up about 18 lead bytes, for about 4500 2-byte primaries, for Han tailorings and/or for Unicode 7.0 additions.

  • Groups below digits should not be compressible, even if they have a single lead byte. Verify that the tools code does that (currency symbols)!

    • Digits will always have at least three lead bytes: first-primary, numeric-primary, possibly shared lead byte for all numbers.

CLDR data

Markus (& Yoshito?)

Done 2012nov28: Remove und-co-ducet tailoring (CldrBug:5464)

  • MD: I think we want to retract that tailoring instead of spending time on it.

  • cldr-dev email 2012nov14 “remove CLDR "ducet" tailoring?”

  • (If we remove it, then we should probably change the LDML spec’s keyword fallback example to use a different keyword value.)

Obsolete: Or else fix und-co-ducet tailoring (CldrBug:5208), run through UCAConformanceTest with DUCET test files

Obsolete because we removed und-co-ducet: Move modifier letters into currency group

  • MD: rather “handle modifier letters”. Having them shift with currencies would be unexpected.

  • Q: Do we even care if the “ducet” tailoring is removed?

  • This could be done later

Collation builder / rule parser

Markus & Yoshito?

Done 2013apr01: Improve weight allocation: Use more byte values (allow 02 in some weight bytes), different limits by level & by weight byte

  • Consider modifying v1 weight allocator to use more byte values (so that it can work with an updated FractionalUCA.txt) and turning off sort key compression to minimize v1 code changes

Done 2013mar: Implement v2 “inverse UCA” to map from reset anchor to next/previous CE for tailoring

Biggest change: From 32-bit CEs with continuation CEs to 64-bit CEs (no continuations, less complexity for v2-only)

Assumption: Incremental development & testing & benchmarking require that we keep v1 code passing all (or most) of its tests until v2 code is ready to fully replace v1.

Q: Plan A or Plan B?

  • Decision: Plan B: Reimplement because the builder code is also buggy, messy, hard to maintain

    • Worse: Turns out v1 approach of building character/string-based tailoring graph caused problems. Replaced for v2 by building CE-based tailoring graph.

  • Neither is trivial; new code vs. keeping it alive for both v1 & v2

  • Current builder/parser has bugs too (not just runtime...), proved hard to extend (e.g., for import & for compact syntax)

  • Plan A means making builder code work for building both v1 & v2 data structures

  • I used to think plan A would save work but I am not so sure any more and am leaning towards plan B

Done 2013may: Consider important bugs (reset has expansion: tickets #9415 & #9593)

Postponed: Consider new features

  • expansion string with its own prefix

  • reset position with prefix

  • context-after (see cldr-users discussion around 2013nov25 about Lao etc.: “Definition of Context-Sensitive Mappings in the CLDR Collation Algorithm”)

Plan A: Refactor

  • Keep rule parser

  • Change current builder to 64-bit CEs, adapt to low-level v1 data structure builder continuing with 32-bit CEs

  • Dynamically use either old or new “inverse UCA” map

  • Dynamically use either old or new weight allocator

Plan B: Reimplement

  • Keep v1 mostly as-is, except (maybe!) to cope with new FractionalUCA.txt (see above)

  • For v2 data structure building only: Implement new parser/token lists etc., copy/modify code or use new design (see design doc)

Builder TODOs


  • Done 2013may: getPrimaryLimitsBefore(ce, isCompressible), sec, ter


  • Done 2013may: copyFromBase(code point)

    • copy all mappings for code point from base, including context

    • enum context, add()

    • share code with CollationSets? move to CollationData?

  • Done 2013jul15: suppressContractions

  • Done 2013jul15: init 0-7F & C0-FF to explicit fallback, to allocate the UTrie2 blocks; Done 2013may: when building, copy-all from base for each such code point which did not get tailored

    • Postponed: or maybe just ASCII (which is always preallocated), and leave other optimization up to the tailorings (measure data size change, propose, change builder, and update the tailorings)

  • Done 2013jul15: Remove hack “tailoring”: Tertiary root CEs 3f30, 3f32 (U+FFF1, U+FFF2)

    • genuca2.cpp & collationtest.cpp & .txt

    • Replace with appropriate @ rules & test tertiary CEs with uppercase bits

    • Look through collationtest.cpp for U+FFF1 etc., clean up

    • Also clean up .txt test of a-z after [last secondary ignorable]

  • Postponed: Maybe look at sets of 4 code points where 1..3 have tailoring mappings, and optimize (copy from base) the other ones as long as they are just single CE32s (without expansions [except Latin mini] or context).

  • Postponed: getJamoCE32s(): Try to prevent [optimize [Jamo]] from counting as anyJamoAssigned. (As of CLDR 24 [2013] the Korean tailoring does not optimize conjoining Jamo.)


  • Done 2013may: support v1 syntax except tailoring [variable top]

  • Done 2013may: support quaternary relations

  • Postponed: support [last Grek], [last punct]  (paper note 20130305)


    • uint32_t scriptFirstPrimaries[num scripts + num special groups]

    • bool haveScriptFirstPrimaries

    • void initScriptFirstPrimaries()

      • independent of script metadata changes (script metadata does not have special groups anyway)

      • enum base FDD1 contractions; check gc --> groups; gc=L --> 0<=script<num

  • Done 2013may: const char *errorReason

  • Done 2013may: error in [import] --> overwrite ParseError index to start of [import]

  • Done 2013oct06 (BundleImporter in collationbuilder.cpp): Write runtime [import]er

  • Done 2013jul16: Make CollationTest % reorder parser use as much of the CollationRuleParser [reorder] parser as possible

  • Done 2013jul16: parse maxVariable

  • Done 2013may: Forbid tailoring U+FFFD, U+FFFE & U+FFFF


  • Done 2013may: Tokens --> CEs

  • Done 2013may: Forbid tailoring to/around unassigned code points

  • Done 2013jul18: Adjust special reset positions according to previous rules

  • Done 2013jul19: Review once more [first variable] and [first regular] and [first trailing]

    • Initially implemented them as boundary CEs

    • I think they should be real root CEs

      • Able to tailor primary-before [first variable] and [first trailing]

        • Unless a rule tailors weak-around FDD1+x

      • Primary-before root [first regular] is still regular, not variable

      • But primary-before the boundary contraction becomes variable

    • verify that there is at least one rootElements entry with an unassigned-implicit primary

  • Done 2013jul15: Case bits

  • Done 2013jul16: Make Hangul work, without context

    • Forbid conjoining Jamo in context-sensitive mappings (in the NFD prefix/str)

    • Forbid conjoining Jamo with expansions — expansions used in search tailorings

    • Build jamoCEs if any of the conjoining Jamo are tailored (done already)

    • Test Hangul & Jamo

  • Done 2013aug04: Support conjoining Jamo with expansions and maybe some context

    • Done 2013jul28: Support expansions

      • Store ce32s, not ces

      • appendCEsFromCE32()

      • copy from base/copy expansions

    • Done 2013jul29: do not add mappings from original rule strings with Hangul syllables (ignoreString())

    • Done 2013jul29: test Jamo expansions

    • Done 2013aug02: probably support at least Jamo L in prefixes, and prefixes on Jamo L — even more: r34008

    • Done 2013aug04: consider using a HANGUL_TAG bit to indicate that none of the Jamos has a special CE32; set it on all Hangul syllables, or for all L* for certain L; inherit it to the tailoring, especially if that does not tailor any Jamos (copy all Hangul CE32s in initForTailoring()?)

    • Postponed: We could probably support Jamo contractions as well as in v1 by putting the V+T into the skipped buffer, recursing on the L, and looping/recursing over the rest of the skipped buffer. The data builder would have to do equivalent processing. The builder should then do at least Hangul tail closure. We would still have the usual problems with other overlap contractions.

    • Done 2013aug03: Support Hangul in prefixes, and in the interior of contractions. The builder would have to do Hangul closure on prefixes. The data builder would have to support Hangul lookup for the closure process.

  • Done 2013jul17: Japanese vs. [hiraganaQ on]

    • “deprecate the hiraganaQuaternary collation attribute”

    • [:Kana:] = [ァ-ヺヽ-ヿㇰ-ㇿ㋐-㋾㌀-㍗ヲ-ッア-ン𛀀]

    • [:Hira:] = [ゝゞぁ-うゔぇ-おゕか-ぐゖけ-ぽ🈀ま-ゆ𛀁ょよゟら-ん]

      • BMP only: [ゝゞぁ-うゔぇ-おゕか-ぐゖけ-ぽま-ゆょよゟら-ん]

    • Consider for now tracking context-sensitive mappings that include Katakana, and look at single-character (frozen) [:Kana:], fetch CEs for all such items, assert quaternary==0, set q=1 in last CE, change mappings → make it work without having to change the tailoring

    • Alternatively, add <<<< to the v1 parser and just treat it like = there. Make the v2 parser ignore [hiraganaQ on]. Change the Japanese tailoring to use <<<< and also keep [hiraganaQ on] for now.

      • Done 2014feb22: Change CLDR Japanese tailoring and re-enable the check in v2 CollationRuleParser forbidding [hiraganaQ on].

  • Done 2013may: &[last regular]

  • Propose to make this equivalent to &[first Hani] where that’s available. (Propose to CLDR & ICU) The actual “last regular” would be available only if the last script is known.

  • Alternative would require changing all Han tailorings.

  • Done 2013aug02: Canonical closure

    • (Learn details of v1 closure process)

    • v1 can do  &x=a &u=â →

      • sort with x: a, å, ...

      • sort with u: â, ấ, ậ, ...

    • Å U+212B Angstrom Sign

    • [:toNFD=/a/:]

    • Closure on suppressed contextual mappings(?) — punted, see documentation TODOs

      • add the set of suppressed base context strings to the canonical closure

      • try to remove suppressed builder context strings

      • the CollationDataBuilder could have a suppress(code point) method which returns the index to the ConditionalCE32, and iterator/getter methods to access the prefix and contraction strings + their ce32

    • Closure exclude Hangul

      • As long as we don’t support context with Jamo/across Hangul, all Hangul syllables should either fall back to the base, or else (especially if any of the conjoining Jamo are tailored) set the Hangul specials and set the jamoCEs.

      • Agreed in discussion 20130617 with Mark: Don’t support context with/across Hangul, document limitation.

    • Builder track UnicodeSet of tailored inputs — seems unnecessary, apply closure immediately

      • str or prefix*str where *=FFFE or FFFF

      • at least inputs that are not NFC-closure-inert

      • exclude purely optimized items (known same as base)

    • v1 ucol_elm.cpp:

      • uprv_uca_canonicalClosure() first closes over composites (done in v2); _enumCategoryRangeClosureCategory(), called from there, uses ucol_strcoll() rather than comparing CEs, which might miss differences in case bits and Hiragana-ness. It also appears to attempt closure with prefixes but only copies one ce32, which is generally broken.

      • Then it looks for the last base character and following ccc!=0 combining mark in each prefix+string input, but it looks only for BMP characters (getFCD16(el.cPoints[j])). It checks for the tccc ((fcd & 0xff) == 0) rather than the lccc; this is probably ok, assuming that these are NFD strings.

      • With the last (baseChar, firstCM) it calls uprv_uca_addTailCanonicalClosures(). That iterates over all combining marks with lower ccc than firstCM (right? and why not ones with higher ccc?), and if baseChar+mark NFC-composes to one BMP(!) composite (which misses some composites because of Composition_Exclusion), then it replaces the last occurrence in prefix+string of firstCM with the new mark, NFC, appends firstCM to both the modified input and the NFC version (so the strings might then not be normalized). Then, if a prefixLookup finds no prefix, adds a mapping from the NFC+firstCM string to the CEs as returned by a collation element iterator working on modifiedInput+firstCM, regardless of whether the new string already maps to those CEs. uprv_uca_setMapCE() always encodes an expansion, even if there is really only one CE; uprv_uca_finalizeAddition() just adds the mapping without further closure. This appears to add only mappings with trailing firstCM, rather than composites that include firstCM, which seems broken.

      • Regardless of the prefixLookup, the function calls uprv_uca_addFCD4AccentedContractions() if the second-to-last UChar(!) of the NFC+firstCM string has lccc==0 (which is true if baseChar+mark composed?), and it calls uprv_uca_addMultiCMContractions() for all but the first iterated combining mark and its composite (what does that do?).

      • Convoluted, not documented well, appears to try to add overlap contractions for contractions that end with ccc!=0 but not others, does not add composites that include firstCM, seems generally buggy.

    • Experimentally disabled ucol_elm.cpp uprv_uca_addTailCanonicalClosures()

    • 2013aug02: checked in new addTailComposites(nfdPrefix, nfdString) -- called by addWithClosure()

  • Done 2013aug07: genrb build every (CLDR) tailoring with the collv2 builder too

    • Done 2013jul29: Ensure that it can at least handle all of the syntax and build something

    • Done 2013aug13: zh.txt:2794: CollationBuilder failed at zhuyin/Sequence rule offset 49: U_UNSUPPORTED_ERROR  tailoring primary after ignorables not supported

    • Done 2014feb21: ko.txt:205: CollationBuilder failed at searchjl/Sequence rule offset 395: U_UNSUPPORTED_ERROR  contextual mappings with conjoining Jamo (hst=L/V/T) not supported

      • email 20130728 “need to support Hangul Jamo contractions?”

      • Might be able to turn these contractions into prefix rules: Make L|L a secondary CE, then make the compound LL expand to regular LL. The first L cannot be a trailing character of a decomposition mapping, and the second L should be able to handle the prefix via recursion. Permit this much context for Jamo but no more. (L can have a prefix but no contraction. L can be in a prefix but no V or T.)

      • Data patched for now, removed Jamo L+L contractions:

      • Done 2013aug05: CLDR ticket proposing data change; v1 & v2 should both be able to handle L|L prefix rules, except v1 cannot handle &L+L=L-L so changing the L-L tailoring would have to wait for v2; maybe make L-after-L equal to a single-secondary-byte combining mark so that we can tailor &mm=G|GG=GG|GG

        • after merging to C trunk: replace Jamo contractions in Korean searchjl collation

          • done 2014feb21 on CLDR trunk, will be integrated into ICU 53

        • v1 apparently fails with &m=L|L too, and we already know it creates ill-formed secondary CEs for &[before 2][first primary ignorable]...

    • Done 2013aug07: Print size stats (toolutil? factored out of genuca2.cpp buildAndWriteBaseData())

    • Done 2013aug07: Compare sizes with v1

    • Done 2013aug07: CollationDataWriter (factored out of genuca2.cpp buildAndWriteBaseData())

  • Postponed: The Korean tailoring probably makes thousands of secondary differences on each Jamo T. Is there any way to share CEs among tailorings that differ on at-least-same-level earlier in an expansion? (On the other hand, this is the tailoring that got smaller the most compared with v1.)

Integrate with C plug-in interface & service registration

Markus Yoshito?

Done 2013oct: Done while replacing old code with new.

Old notes: Might be easier than with v1 because I believe the plug-in and service registration code rely on C++ Collator dispatching. v1 UCollator has a “delegate” C++ Collator, v2 should just go through C++ Collator anyway.

Port to Java

Markus & Yoshito


  • Implementation package:

  • Use long for 64-bit CE

  • uint32_t primary? which is better/faster?

      • long p = ce >>> 32, simple comparisons

      • int p = (int)(ce >> 32), simple “==” but need to use “trick” for “<”

    • long primary

    • int ce32

    • Pitfall:

      • C++ cast from uint32_t to int64_t zero-extends, so (int64_t)p and (int64_t)(sec << 16) is fine and efficient.

      • Java cast from int to long sign-extends, so we need to either mask off the high bits after the cast – (long)p & 0xffffffffL – or cast to long before shifting into the sign bit – ((long)sec << 16).

        • Search for mask values: 0x[89abcdef][0-9a-f]{7}[^L]

        • Of course, this is irrelevant if we shift-left-by-32 the value after casting to long.

  • CollationIterator.handleNextCE32() could return a long with the code point in the upper half (bits 52..32 or -1, use signed “>>”) and the ce32 in the lower half (bits 31..0)

    • done, see helpers in the base CollationIterator:

      • long makeCodePointAndCE32Pair(int c, int ce32)

      • NO_CP_AND_CE32 which is the same as makeCodePointAndCE32Pair(U_SENTINEL=-1, Collation.FALLBACK_CE32)

  • work on String or CharSequence?

    • Keep the public API with String and use CharSequence in the implementation.

  • Port C++ “public” to Java package-private visibility – until we find that something is indeed needed from another package.

  • CharsTrie works on CharSequence, not on char[] – CharsTrie(CharSequence trieChars, int offset)

  • Java: Port SharedObject or use some JDK reference counting?

    • Search for “Java atomic increment” and “Java shared mutable” etc.

    • Java Collator does not get deleted, removeRef() won’t be called?!

      • Write finalize() { settings.removeRef(); settings = null; } – seems no worse than usual Java memory management.

    • Ported SharedObject, see usage comments there.

    • Revisit; maybe just shallow-clone the settings each time we want to modify them, and remove SharedObject?

      • That would always clone the CollationSettings itself, and its fastLatinPrimaries

  • Markus messed up some global search&replace.

    • Some function calls like switchToForward(errorCode) lost not just the “errorCode” but also the parentheses, so they look like variables. Just add “()”...

    • Some spaces removed that I shouldn’t have, like in “extends SomeClass”.

  • Check old code for Exception types and messages. We might want to try to match types, but we should be free to improve/clarify the messages.


  • use final and @Override

  • before you start porting a file, put your name after the file name in the list below

If something needs to be changed in C++, note it here.

  • TODO(Markus, after ICU 53): machine-generate initializers by icu/tools/unicode/c/genuca/genuca.cpp

Other changes to be made in ICU4J

  • TODO(after ICU 53): create a common, public constant somewhere in ICU4J corresponding to C/C++ U_SENTINEL? (move Collation.SENTINEL_CP there)

    • FYI: there is – document <0, and maybe make it equal to the new constant?

    • there is also UnicodeSetIterator.IS_STRING=-1

    • maybe create a new public class CodePoint with SENTINEL, static String toString(int), isSurrogate(int), ...?

    • or UCharacter.SENTINEL?

  • TODO(after ICU 53): propose widening CanonicalIterator to take CharSequence input -> for CollationBuilder, check other callers

  • Done 2014mar04: use ICU-specific exceptions (, document them where appropriate

    • Normalizer2Impl.load() sometimes throws an IOException which is immediately caught and then re-thrown as a RuntimeException.

  • TODO(after ICU 53): ask Mark: AlphabeticIndexTest.TestFirstScriptCharacters() is now pretty much circular with the implementation code, but it’s harmless; keep or delete?

  • TODO(after ICU 53): consider moving CollationKeyByteSink into RawCollationKey as nested class, with an instance cached in the key; and maybe similar in C++

  • TODO(after ICU 53): we can probably simplify BOCSU.getNegDivMod() because Java specifies the div/mod behavior


  • - Markus - done

  • - Yoshito - done

  • - Markus - done

  • - Markus - done

  • - Markus - done

  • - Markus - done

  • - Markus - done

  • extends CollationIterator - Markus - done

    • - Markus - done

  • extends CollationIterator - Markus - done

    • Take & use ICU UCharacterIterator as before.


  • - Yoshito - done

  • - Yoshito - done

    • only CollationLoader class, ucol_getDisplayName, etc.. are not included

  • - Markus - done

  • - Markus - done

  • - Markus - done

  • - Markus - done

  • - Yoshito - done

    • See Normalizer2Impl.addLcccChars(), addPropertyStarts(), addCanonIterPropertyStarts() for examples of how to iterate the newer type of Trie in Java (C++ UTrie2).

  • - Markus - done

  • - Yoshito - done

    • Somewhat similar to, see comments above.

  • icudata.jar - Markus - done

  • delete - Markus - done

    • check if the UnicodeTools still depend on it (after svn update of UnicodeTools and also CLDR code) - done


Check i18n & i18n/unicode diffs, merge into existing Java API classes.

Make sure to preserve existing Java public/protected signatures, especially argument & return types.

Note: Initially, I (Markus) copied all files into .impl.coll, to make it easier to grab all files for “global” edits. Eventually, pieces of semi-ported code in classes that go elsewhere need to be merged into those existing classes.

  • - Markus - done

  • - Markus - done

    • using CollationBuffer for thread safety of frozen instances, as before

  • - Yoshito -

    • The old Java code seems to contain code for both the low-level collation algorithm (which in the new code is in as well as for the utility CollationElementIterator API. [In the old C++ code, the low-level code was in ucol.cpp.]

    • In C/C++, the old C++ coleitr.h/.cpp was only a shim over C ucoleitr.h/.cpp which contained the logic for the C UColElements API. In the new C++ code, the CollationElementIterator class has the API logic again, and uses an appropriate CollationIterator subclass, and the C code is back to just a wrapper.

    • In C++, the C code still has special code for internal use by UStringSearch. This was more lightly modified than other collation code. Some of it was moved to other files for better layering.

    • Nearly all of this C/C++ stuff should be collected in the file, except where some of it moved into a C/C++ search code file (check the source/i18n diffs).

    • It’s probably best to start by moving/porting CollationElementIterator API functions by copying equivalent bits and pieces from, and working top-down from there. Then delete unused code. (That’s pretty much what Markus did with the RuleBasedCollator.)

    • Markus already moved over a few helper functions and the getMaxExpansion() stuff (in order to make progress on the RBC).

    • Done 2014feb26: merge in API doc changes from C++ i18n/unicode diffs (coleitr.h, ucoleitr.h); fix userguide links, refer to the “root collator” rather than “UCA” or “DUCET” where appropriate

    • Done 2014feb26: throw new RuntimeException("Illegal change of direction") -> IllegalStateException

  • TODO(Markus, future): RBC setters: Change void setXyz() to returning this=RBC. Consider pushing APIs down to Collator, too (covariant setters). (Note: C++ virtual setAttribute() is already in the base class and returns void. May not be worth duplicating for a chainable version.)

Port changes in other existing files

  • common - Markus - done

  • common - Markus - n/a

    • C++ had unorm_it.h/.c with UNormIterator which got deleted. Is there something like it in Java?

    • -> unable to find it, and it looks like the old Java code never used a CharacterIterator for collation (CEI apparently always just extracted the underlying string)

  • i18n (not search code) - Markus - done

    • only AlphabeticIndex improvements, aside from core collation and search

Search code changes

  • - Yoshito - done

  • ucoleitr.h/cpp copied into; some of the C++ functionality is only there


Get rid of all errorReason fields and getters: Add that information to the exception message string. Throw the exception from inside existing (in the new code) setParseError() functions etc. - done

  • - Markus - done

  • - Markus - done

  • - Markus - done

  • - Markus - done

  • - Markus - done

  • delete & CollationParsedRuleBuilder - Markus - done

Do not port to Java

  • C API, except if there is no C++ API and we need to port C to Java

  • tools/genuca2

  • CollationBaseDataBuilder: used only by genuca2 tool

  • UTF8CollationIterator, compareUTF8(), ...

  • Handling of NUL-terminated strings

  • Data swapping

  • Java Collator and RBC have no equivalent for C++ RBC::cloneBinary() which serializes the collator data and settings into a binary blob. It also does not write .res files nor


  • - Yoshito - done

    • There already is a – Markus deleted the old-data-driven-test code that was there – pour the new CollationTest code in there.

    • see UCAConformanceTest.openTestFile(); and/or see how Andy finds & loads UTF-8 .txt files for rbbi & regex testing

  • collationtest.txt - Markus - done

  • CollationTest_*.txt - Markus - done

  • other test changes: see C/C++diffs - Markus - done

    • modify as in cintltst:

      • custrtst.c - n/a

      • cmsccoll.c - - done

      • citertst.c - - done

      • creststn.c - n/a

      • callcoll.c - - done

      • crestst.c - n/a

      • capitst.c - - done

      • udatatst.c - n/a

    • modify as in intltest:

      • colldata.cpp - n/a

      • intltest.cpp - n/a

      • ucaconf.cpp - - done

      • ssearch.cpp - n/a

      • regcoll.cpp - - done

      • tscoll.cpp - n/a

      • alphaindextst.cpp - - done

      • itercoll.cpp - - done

      • svccoll.cpp - - n/a

      • thcoll.cpp - n/a

      • apicoll.cpp - - done

    • delete as in intltest:

      • cntabcol.cpp - unable to find equivalent Java test code - n/a

      • dadrcoll.cpp - remove old data-driven test code from - done


  • Review TODOs in collation .java files (note: some are also in the C++ code) - Markus - done

  • Review copyright dates - Markus - done

    • Copyright of new Java files should reflect C++ where they were ported from, or the start of the Java port?

    • Markus started the Java port on 2014-jan-13.

  • Review @since/@author tags. - Markus - done (reverted to C style comments)

  • Done 2014mar03: Merge Java port into trunk

More Tests

Overlap of contractions vs. decomposition

  • Richard Wordingham, unicode list 20130206: Just add <U+0302, U+0067> to the default set of collating elements. The NFC string <U+011D, U+011D, U+011D> then consists of the four collating elements <U+0067>, <U+0302, U+0067>, <U+0302, U+0067>, <U+0302>, and it is impossible to handle the NFC string without using NFD normalisation.


  • Test [optimize [0-10ffff]]

  • Test [suppressContractions [0-10ffff]]

  • Test that for a character with both prefixes (p|c) and contractions (p|ci), if it has no-prefix contractions (ch) and has prefixes without no-suffix mappings (no p|c), the no-prefix contractions are not repeated for each such prefix (the set should not include p|ch).


  • Done 2013nov11: iterate over CollationRootElements? skip primary ranges?

→ CollationRootElementsTest  (paper note 20130225)

  • Done 2013nov11: Iterate over CollationRootElements

  • Done 2013nov11: Check CE validity

  • Check that for each primary the one before & after is returned (within given limitations)

  • Done 2013nov11: For each primary range, test edges and one internal CE, or better all; test that we reach the range end exactly when iterating “after” through the range

  • Check secondary/tertiary before & after too

  • Done 2013nov11: Check that between two CEs there is a tailoring gap of appropriate strength (try to allocate at least one item between them)

Obsolete 2013dec06: Changed the data builder to use the runtime collation implementation for fetching build-time CEs. As a result, there is only one algorithm implementation, and no need to test a second one.

  • CollationDataBuilder.getCEs() should get same CEs (for NFD string) as CollationIterator on built CollationData

  • try with just baseData, optimize some (copy from base to builder), try with some tailoring

  • maybe even run the UCAConformanceTest with it

  • would need to either run the CollationBuilder to just before where it calls build() on the data builder, or somehow copy mappings from CollationData

Postponed: More tests

  • genrb --omitCollationRules

    • Test again after trunk integration that this works.

    • Try to make test code work with this option, except for missing-data warnings.

  • Try combinations of base vs. tailoring for discontiguous & nested contractions, to test fallbacks and fetching inner CEs from the original data.

  • Test CODAN with first digit in base and others in tailoring.

  • CollationIterator::numCpFwd: Test this with contiguous & discontiguous contractions and digit specials! Try to start iterating backwards from all code point boundaries inside varied text.

  • For each tailoring in the data, which was built by ICU4C: In ICU4J, build from rules and check that the data is exactly the same.

  • fast Latin: at least data-driven tests: try both with and without Latin fastpath

  • Withdrawn 2014mar01 (not worth the time to find this bug in old code): CollationIterator::previousCEUnsafe(): Verify that the v1 code uses a backward buffer and gets into trouble with a prefix match that would need to move before the backward buffer.

  • Done 2014mar01 (could not find bad behavior with old-code collation demo): CollationKeys: (Tertiary weights with caseFirst=upperFirst) Does v1 handle 03 & 04 tertiary weights properly? 02? Try &[before 3]a<<<x and U+FFFE with all case settings.


LDML spec

Done 2013sep04: document new case bits algorithm

Done 2014mar10: [first variable] and [first regular] and [first trailing] should be the first real such CEs, not the boundary CEs.

Done 2014mar10: Forbid tailoring to [last trailing]. (That’s U+FFFF.)

Done 2013sep04: Special reset positions always resolve to single CEs. They can be affected by rules that tailor expansions.

Update the spreadsheet of special byte values. Include sec/ter boundaries. Add such a table into the LDML spec, as far as is relevant for FractionalUCA.txt.

At least document FractionalUCA.txt compressible lead bytes, range of sec/ter bytes for compression.

Rule syntax: (setting | comment | rule chain)*

rule chain = reset (comment | relation)+  // at least one relation

relation = operator [prefix ‘|’] string [‘/’ extension]

Done 2014mar10: Script reordering after check for variableTop

Gotcha: &ĉ<c<<<C yields c <2 ĉ because of canonical closure!

Done 2014mar10: CLDR Coll Alg also adds spec for

  • case weights in a separate level or as high-order components in tertiary level, see 3.13 Case Parameters, which enable

    • lowercase first & uppercase first (caseFirst setting)

    • “ignore accents” (strength=primary & caseLevel=on)

    • “ignore variants” (strength=secondary & caseLevel=on)

  • reordering groups and their boundaries, for maxVariable and script reordering

Done 2014mar10: Case Param. notes

  • p+c ignores sec because it wants to “ignore accents”

  • s+c ignores ter for equivalent reason: “ignore variants” (except case)

  • t+c or caseFirst: ter CEs need high case weight for WF2; together with usual high-tertiary-weight the combined ct is high too

ICU User Guide

Hangul limitation

  • limited contextual mappings with conjoining Jamo

  • verify that it’s a new limitation, document version numbers

Closure limitations

  • no closure on suppressContractions set

  • tail closure on last starter that is NFC_QC=Yes and not a Jamo L

  • no other overlap closures

ICU Data -> new data formats

Forbid use of [last trailing]. (That’s U+FFFF.)

Forbid tailoring to [last implicit].

Done 2014mar30: document byte values ( , maybe in LDML spec, maybe also ICU-specific stuff in User Guide (from

ICU pri lead bytes E0..FF different from FractionalUCA.txt.

Document genrb options in collation and/or ICU Data chapters: --omitCollationRules --includeUnihanColl --noBinaryCollation

Email to self on 2012nov06:

See not-done LDML spec notes above. Maybe just in the ICU User Guide?

ICU API docs

Done 2014mar04: Update API docs for hiraganaQuaternary attribute.

ICU Readme & download page

  • Done 2014feb26

  • Java Collator: getters for strength, decomposition mode, and locales return hardcoded default values; their setters do nothing

  • Java, Object) now works with CharSequence, not just String

  • Passes full UCA conformance tests now

  • Data 1.1MB smaller; trunk at r35221: 4.7MB, with collv2 merged in: 3.6MB


  • Done 2013oct: Increment runtime & builder version numbers.

  • Obsolete 2013nov09: Can we remove the UTrie(1) builder code once collation has switched over to UTrie2?

    • no, still in use

    • the RBBISetBuilder still uses a UTrie(1)

    • gensprep builds a UTrie(1)

  • Done 2012nov26: remove unorm_it.h / unorm_openIter()

  • Done 2013dec12: TODOs in AlphabeticIndex and its tests