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Upgrade blevesearch to v0.8.1 (#9177)

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Mura Li 2019-11-27 17:23:33 +08:00 • committed by Lauris BH
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commit 9591185c8f
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# levenshtein
levenshtein automaton
This package makes it fast and simple to build a finite determinic automaton that computes the levenshtein distance from a given string.
# Sample usage:
```
// build a re-usable builder
lb := NewLevenshteinAutomatonBuilder(2, false)
origTerm := "couchbasefts"
dfa := lb.BuildDfa("couchbases", 2)
ed := dfa.eval([]byte(origTerm))
if ed.distance() != 2 {
log.Errorf("expected distance 2, actual: %d", ed.distance())
}
```
This implementation is inspired by [blog post](https://fulmicoton.com/posts/levenshtein/) and is intended to be
a port of original rust implementation: https://github.com/tantivy-search/levenshtein-automata
Micro Benchmark Results against the current vellum/levenshtein is as below.
```
BenchmarkNewEditDistance1-8 30000 52684 ns/op 89985 B/op 295 allocs/op
BenchmarkOlderEditDistance1-8 10000 132931 ns/op 588892 B/op 363 allocs/op
BenchmarkNewEditDistance2-8 10000 199127 ns/op 377532 B/op 1019 allocs/op
BenchmarkOlderEditDistance2-8 2000 988109 ns/op 4236609 B/op 1898 allocs/op
```

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vendor/github.com/couchbase/vellum/levenshtein/alphabet.go generated vendored Normal file
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// Copyright (c) 2018 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package levenshtein
import (
"fmt"
"sort"
"unicode/utf8"
)
type FullCharacteristicVector []uint32
func (fcv FullCharacteristicVector) shiftAndMask(offset, mask uint32) uint32 {
bucketID := offset / 32
align := offset - bucketID*32
if align == 0 {
return fcv[bucketID] & mask
}
left := fcv[bucketID] >> align
right := fcv[bucketID+1] << (32 - align)
return (left | right) & mask
}
type tuple struct {
char rune
fcv FullCharacteristicVector
}
type sortRunes []rune
func (s sortRunes) Less(i, j int) bool {
return s[i] < s[j]
}
func (s sortRunes) Swap(i, j int) {
s[i], s[j] = s[j], s[i]
}
func (s sortRunes) Len() int {
return len(s)
}
func sortRune(r []rune) []rune {
sort.Sort(sortRunes(r))
return r
}
type Alphabet struct {
charset []tuple
index uint32
}
func (a *Alphabet) resetNext() {
a.index = 0
}
func (a *Alphabet) next() (rune, FullCharacteristicVector, error) {
if int(a.index) >= len(a.charset) {
return 0, nil, fmt.Errorf("eof")
}
rv := a.charset[a.index]
a.index++
return rv.char, rv.fcv, nil
}
func dedupe(in string) string {
lookUp := make(map[rune]struct{}, len(in))
var rv string
for len(in) > 0 {
r, size := utf8.DecodeRuneInString(in)
in = in[size:]
if _, ok := lookUp[r]; !ok {
rv += string(r)
lookUp[r] = struct{}{}
}
}
return rv
}
func queryChars(qChars string) Alphabet {
chars := dedupe(qChars)
inChars := sortRune([]rune(chars))
charsets := make([]tuple, 0, len(inChars))
for _, c := range inChars {
tempChars := qChars
var bits []uint32
for len(tempChars) > 0 {
var chunk string
if len(tempChars) > 32 {
chunk = tempChars[0:32]
tempChars = tempChars[32:]
} else {
chunk = tempChars
tempChars = tempChars[:0]
}
chunkBits := uint32(0)
bit := uint32(1)
for _, chr := range chunk {
if chr == c {
chunkBits |= bit
}
bit <<= 1
}
bits = append(bits, chunkBits)
}
bits = append(bits, 0)
charsets = append(charsets, tuple{char: c, fcv: FullCharacteristicVector(bits)})
}
return Alphabet{charset: charsets}
}

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// Copyright (c) 2018 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package levenshtein
import (
"fmt"
"math"
)
const SinkState = uint32(0)
type DFA struct {
transitions [][256]uint32
distances []Distance
initState int
ed uint8
}
/// Returns the initial state
func (d *DFA) initialState() int {
return d.initState
}
/// Returns the Levenshtein distance associated to the
/// current state.
func (d *DFA) distance(stateId int) Distance {
return d.distances[stateId]
}
/// Returns the number of states in the `DFA`.
func (d *DFA) numStates() int {
return len(d.transitions)
}
/// Returns the destination state reached after consuming a given byte.
func (d *DFA) transition(fromState int, b uint8) int {
return int(d.transitions[fromState][b])
}
func (d *DFA) eval(bytes []uint8) Distance {
state := d.initialState()
for _, b := range bytes {
state = d.transition(state, b)
}
return d.distance(state)
}
func (d *DFA) Start() int {
return int(d.initialState())
}
func (d *DFA) IsMatch(state int) bool {
if _, ok := d.distance(state).(Exact); ok {
return true
}
return false
}
func (d *DFA) CanMatch(state int) bool {
return state > 0 && state < d.numStates()
}
func (d *DFA) Accept(state int, b byte) int {
return int(d.transition(state, b))
}
// WillAlwaysMatch returns if the specified state will always end in a
// matching state.
func (d *DFA) WillAlwaysMatch(state int) bool {
return false
}
func fill(dest []uint32, val uint32) {
for i := range dest {
dest[i] = val
}
}
func fillTransitions(dest *[256]uint32, val uint32) {
for i := range dest {
dest[i] = val
}
}
type Utf8DFAStateBuilder struct {
dfaBuilder *Utf8DFABuilder
stateID uint32
defaultSuccessor []uint32
}
func (sb *Utf8DFAStateBuilder) addTransitionID(fromStateID uint32, b uint8,
toStateID uint32) {
sb.dfaBuilder.transitions[fromStateID][b] = toStateID
}
func (sb *Utf8DFAStateBuilder) addTransition(in rune, toStateID uint32) {
fromStateID := sb.stateID
chars := []byte(string(in))
lastByte := chars[len(chars)-1]
for i, ch := range chars[:len(chars)-1] {
remNumBytes := len(chars) - i - 1
defaultSuccessor := sb.defaultSuccessor[remNumBytes]
intermediateStateID := sb.dfaBuilder.transitions[fromStateID][ch]
if intermediateStateID == defaultSuccessor {
intermediateStateID = sb.dfaBuilder.allocate()
fillTransitions(&sb.dfaBuilder.transitions[intermediateStateID],
sb.defaultSuccessor[remNumBytes-1])
}
sb.addTransitionID(fromStateID, ch, intermediateStateID)
fromStateID = intermediateStateID
}
toStateIDDecoded := sb.dfaBuilder.getOrAllocate(original(toStateID))
sb.addTransitionID(fromStateID, lastByte, toStateIDDecoded)
}
type Utf8StateId uint32
func original(stateId uint32) Utf8StateId {
return predecessor(stateId, 0)
}
func predecessor(stateId uint32, numSteps uint8) Utf8StateId {
return Utf8StateId(stateId*4 + uint32(numSteps))
}
// Utf8DFABuilder makes it possible to define a DFA
// that takes unicode character, and build a `DFA`
// that operates on utf-8 encoded
type Utf8DFABuilder struct {
index []uint32
distances []Distance
transitions [][256]uint32
initialState uint32
numStates uint32
maxNumStates uint32
}
func withMaxStates(maxStates uint32) *Utf8DFABuilder {
rv := &Utf8DFABuilder{
index: make([]uint32, maxStates*2+100),
distances: make([]Distance, 0, maxStates),
transitions: make([][256]uint32, 0, maxStates),
maxNumStates: maxStates,
}
for i := range rv.index {
rv.index[i] = math.MaxUint32
}
return rv
}
func (dfab *Utf8DFABuilder) allocate() uint32 {
newState := dfab.numStates
dfab.numStates++
dfab.distances = append(dfab.distances, Atleast{d: 255})
dfab.transitions = append(dfab.transitions, [256]uint32{})
return newState
}
func (dfab *Utf8DFABuilder) getOrAllocate(state Utf8StateId) uint32 {
if int(state) >= cap(dfab.index) {
cloneIndex := make([]uint32, int(state)*2)
copy(cloneIndex, dfab.index)
dfab.index = cloneIndex
}
if dfab.index[state] != math.MaxUint32 {
return dfab.index[state]
}
nstate := dfab.allocate()
dfab.index[state] = nstate
return nstate
}
func (dfab *Utf8DFABuilder) setInitialState(iState uint32) {
decodedID := dfab.getOrAllocate(original(iState))
dfab.initialState = decodedID
}
func (dfab *Utf8DFABuilder) build(ed uint8) *DFA {
return &DFA{
transitions: dfab.transitions,
distances: dfab.distances,
initState: int(dfab.initialState),
ed: ed,
}
}
func (dfab *Utf8DFABuilder) addState(state, default_suc_orig uint32,
distance Distance) (*Utf8DFAStateBuilder, error) {
if state > dfab.maxNumStates {
return nil, fmt.Errorf("State id is larger than maxNumStates")
}
stateID := dfab.getOrAllocate(original(state))
dfab.distances[stateID] = distance
defaultSuccID := dfab.getOrAllocate(original(default_suc_orig))
// creates a chain of states of predecessors of `default_suc_orig`.
// Accepting k-bytes (whatever the bytes are) from `predecessor_states[k-1]`
// leads to the `default_suc_orig` state.
predecessorStates := []uint32{defaultSuccID,
defaultSuccID,
defaultSuccID,
defaultSuccID}
for numBytes := uint8(1); numBytes < 4; numBytes++ {
predecessorState := predecessor(default_suc_orig, numBytes)
predecessorStateID := dfab.getOrAllocate(predecessorState)
predecessorStates[numBytes] = predecessorStateID
succ := predecessorStates[numBytes-1]
fillTransitions(&dfab.transitions[predecessorStateID], succ)
}
// 1-byte encoded chars.
fill(dfab.transitions[stateID][0:192], predecessorStates[0])
// 2-bytes encoded chars.
fill(dfab.transitions[stateID][192:224], predecessorStates[1])
// 3-bytes encoded chars.
fill(dfab.transitions[stateID][224:240], predecessorStates[2])
// 4-bytes encoded chars.
fill(dfab.transitions[stateID][240:256], predecessorStates[3])
return &Utf8DFAStateBuilder{
dfaBuilder: dfab,
stateID: stateID,
defaultSuccessor: predecessorStates}, nil
}

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vendor/github.com/couchbase/vellum/levenshtein/levenshtein.go generated vendored Normal file
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// Copyright (c) 2018 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package levenshtein
import "fmt"
// StateLimit is the maximum number of states allowed
const StateLimit = 10000
// ErrTooManyStates is returned if you attempt to build a Levenshtein
// automaton which requires too many states.
var ErrTooManyStates = fmt.Errorf("dfa contains more than %d states",
StateLimit)
// LevenshteinAutomatonBuilder wraps a precomputed
// datastructure that allows to produce small (but not minimal) DFA.
type LevenshteinAutomatonBuilder struct {
pDfa *ParametricDFA
}
// NewLevenshteinAutomatonBuilder creates a
// reusable, threadsafe Levenshtein automaton builder.
// `maxDistance` - maximum distance considered by the automaton.
// `transposition` - assign a distance of 1 for transposition
//
// Building this automaton builder is computationally intensive.
// While it takes only a few milliseconds for `d=2`, it grows
// exponentially with `d`. It is only reasonable to `d <= 5`.
func NewLevenshteinAutomatonBuilder(maxDistance uint8,
transposition bool) (*LevenshteinAutomatonBuilder, error) {
lnfa := newLevenshtein(maxDistance, transposition)
pdfa, err := fromNfa(lnfa)
if err != nil {
return nil, err
}
return &LevenshteinAutomatonBuilder{pDfa: pdfa}, nil
}
// BuildDfa builds the levenshtein automaton for serving
// queries with a given edit distance.
func (lab *LevenshteinAutomatonBuilder) BuildDfa(query string,
fuzziness uint8) (*DFA, error) {
return lab.pDfa.buildDfa(query, fuzziness, false)
}
// MaxDistance returns the MaxEdit distance supported by the
// LevenshteinAutomatonBuilder builder.
func (lab *LevenshteinAutomatonBuilder) MaxDistance() uint8 {
return lab.pDfa.maxDistance
}

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vendor/github.com/couchbase/vellum/levenshtein/levenshtein_nfa.go generated vendored Normal file
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// Copyright (c) 2018 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package levenshtein
import (
"math"
"sort"
)
/// Levenshtein Distance computed by a Levenshtein Automaton.
///
/// Levenshtein automata can only compute the exact Levenshtein distance
/// up to a given `max_distance`.
///
/// Over this distance, the automaton will invariably
/// return `Distance::AtLeast(max_distance + 1)`.
type Distance interface {
distance() uint8
}
type Exact struct {
d uint8
}
func (e Exact) distance() uint8 {
return e.d
}
type Atleast struct {
d uint8
}
func (a Atleast) distance() uint8 {
return a.d
}
func characteristicVector(query []rune, c rune) uint64 {
chi := uint64(0)
for i := 0; i < len(query); i++ {
if query[i] == c {
chi |= 1 << uint64(i)
}
}
return chi
}
type NFAState struct {
Offset uint32
Distance uint8
InTranspose bool
}
type NFAStates []NFAState
func (ns NFAStates) Len() int {
return len(ns)
}
func (ns NFAStates) Less(i, j int) bool {
if ns[i].Offset != ns[j].Offset {
return ns[i].Offset < ns[j].Offset
}
if ns[i].Distance != ns[j].Distance {
return ns[i].Distance < ns[j].Distance
}
return !ns[i].InTranspose && ns[j].InTranspose
}
func (ns NFAStates) Swap(i, j int) {
ns[i], ns[j] = ns[j], ns[i]
}
func (ns *NFAState) imply(other NFAState) bool {
transposeImply := ns.InTranspose
if !other.InTranspose {
transposeImply = !other.InTranspose
}
deltaOffset := ns.Offset - other.Offset
if ns.Offset < other.Offset {
deltaOffset = other.Offset - ns.Offset
}
if transposeImply {
return uint32(other.Distance) >= (uint32(ns.Distance) + deltaOffset)
}
return uint32(other.Distance) > (uint32(ns.Distance) + deltaOffset)
}
type MultiState struct {
states []NFAState
}
func (ms *MultiState) States() []NFAState {
return ms.states
}
func (ms *MultiState) Clear() {
ms.states = ms.states[:0]
}
func newMultiState() *MultiState {
return &MultiState{states: make([]NFAState, 0)}
}
func (ms *MultiState) normalize() uint32 {
minOffset := uint32(math.MaxUint32)
for _, s := range ms.states {
if s.Offset < minOffset {
minOffset = s.Offset
}
}
if minOffset == uint32(math.MaxUint32) {
minOffset = 0
}
for i := 0; i < len(ms.states); i++ {
ms.states[i].Offset -= minOffset
}
sort.Sort(NFAStates(ms.states))
return minOffset
}
func (ms *MultiState) addStates(nState NFAState) {
for _, s := range ms.states {
if s.imply(nState) {
return
}
}
i := 0
for i < len(ms.states) {
if nState.imply(ms.states[i]) {
ms.states = append(ms.states[:i], ms.states[i+1:]...)
} else {
i++
}
}
ms.states = append(ms.states, nState)
}
func extractBit(bitset uint64, pos uint8) bool {
shift := bitset >> pos
bit := shift & 1
return bit == uint64(1)
}
func dist(left, right uint32) uint32 {
if left > right {
return left - right
}
return right - left
}
type LevenshteinNFA struct {
mDistance uint8
damerau bool
}
func newLevenshtein(maxD uint8, transposition bool) *LevenshteinNFA {
return &LevenshteinNFA{mDistance: maxD,
damerau: transposition,
}
}
func (la *LevenshteinNFA) maxDistance() uint8 {
return la.mDistance
}
func (la *LevenshteinNFA) msDiameter() uint8 {
return 2*la.mDistance + 1
}
func (la *LevenshteinNFA) initialStates() *MultiState {
ms := MultiState{}
nfaState := NFAState{}
ms.addStates(nfaState)
return &ms
}
func (la *LevenshteinNFA) multistateDistance(ms *MultiState,
queryLen uint32) Distance {
minDistance := Atleast{d: la.mDistance + 1}
for _, s := range ms.states {
t := s.Distance + uint8(dist(queryLen, s.Offset))
if t <= uint8(la.mDistance) {
if minDistance.distance() > t {
minDistance.d = t
}
}
}
if minDistance.distance() == la.mDistance+1 {
return Atleast{d: la.mDistance + 1}
}
return minDistance
}
func (la *LevenshteinNFA) simpleTransition(state NFAState,
symbol uint64, ms *MultiState) {
if state.Distance < la.mDistance {
// insertion
ms.addStates(NFAState{Offset: state.Offset,
Distance: state.Distance + 1,
InTranspose: false})
// substitution
ms.addStates(NFAState{Offset: state.Offset + 1,
Distance: state.Distance + 1,
InTranspose: false})
n := la.mDistance + 1 - state.Distance
for d := uint8(1); d < n; d++ {
if extractBit(symbol, d) {
// for d > 0, as many deletion and character match
ms.addStates(NFAState{Offset: state.Offset + 1 + uint32(d),
Distance: state.Distance + d,
InTranspose: false})
}
}
if la.damerau && extractBit(symbol, 1) {
ms.addStates(NFAState{
Offset: state.Offset,
Distance: state.Distance + 1,
InTranspose: true})
}
}
if extractBit(symbol, 0) {
ms.addStates(NFAState{Offset: state.Offset + 1,
Distance: state.Distance,
InTranspose: false})
}
if state.InTranspose && extractBit(symbol, 0) {
ms.addStates(NFAState{Offset: state.Offset + 2,
Distance: state.Distance,
InTranspose: false})
}
}
func (la *LevenshteinNFA) transition(cState *MultiState,
dState *MultiState, scv uint64) {
dState.Clear()
mask := (uint64(1) << la.msDiameter()) - uint64(1)
for _, state := range cState.states {
cv := (scv >> state.Offset) & mask
la.simpleTransition(state, cv, dState)
}
sort.Sort(NFAStates(dState.states))
}
func (la *LevenshteinNFA) computeDistance(query, other []rune) Distance {
cState := la.initialStates()
nState := newMultiState()
for _, i := range other {
nState.Clear()
chi := characteristicVector(query, i)
la.transition(cState, nState, chi)
cState, nState = nState, cState
}
return la.multistateDistance(cState, uint32(len(query)))
}

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vendor/github.com/couchbase/vellum/levenshtein/parametric_dfa.go generated vendored Normal file
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@ -0,0 +1,349 @@
// Copyright (c) 2018 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package levenshtein
import (
"crypto/md5"
"encoding/json"
"fmt"
"math"
)
type ParametricState struct {
shapeID uint32
offset uint32
}
func newParametricState() ParametricState {
return ParametricState{}
}
func (ps *ParametricState) isDeadEnd() bool {
return ps.shapeID == 0
}
type Transition struct {
destShapeID uint32
deltaOffset uint32
}
func (t *Transition) apply(state ParametricState) ParametricState {
ps := ParametricState{
shapeID: t.destShapeID}
// don't need any offset if we are in the dead state,
// this ensures we have only one dead state.
if t.destShapeID != 0 {
ps.offset = state.offset + t.deltaOffset
}
return ps
}
type ParametricStateIndex struct {
stateIndex []uint32
stateQueue []ParametricState
numOffsets uint32
}
func newParametricStateIndex(queryLen,
numParamState uint32) ParametricStateIndex {
numOffsets := queryLen + 1
if numParamState == 0 {
numParamState = numOffsets
}
maxNumStates := numParamState * numOffsets
psi := ParametricStateIndex{
stateIndex: make([]uint32, maxNumStates),
stateQueue: make([]ParametricState, 0, 150),
numOffsets: numOffsets,
}
for i := uint32(0); i < maxNumStates; i++ {
psi.stateIndex[i] = math.MaxUint32
}
return psi
}
func (psi *ParametricStateIndex) numStates() int {
return len(psi.stateQueue)
}
func (psi *ParametricStateIndex) maxNumStates() int {
return len(psi.stateIndex)
}
func (psi *ParametricStateIndex) get(stateID uint32) ParametricState {
return psi.stateQueue[stateID]
}
func (psi *ParametricStateIndex) getOrAllocate(ps ParametricState) uint32 {
bucket := ps.shapeID*psi.numOffsets + ps.offset
if bucket < uint32(len(psi.stateIndex)) &&
psi.stateIndex[bucket] != math.MaxUint32 {
return psi.stateIndex[bucket]
}
nState := uint32(len(psi.stateQueue))
psi.stateQueue = append(psi.stateQueue, ps)
psi.stateIndex[bucket] = nState
return nState
}
type ParametricDFA struct {
distance []uint8
transitions []Transition
maxDistance uint8
transitionStride uint32
diameter uint32
}
func (pdfa *ParametricDFA) initialState() ParametricState {
return ParametricState{shapeID: 1}
}
// Returns true iff whatever characters come afterward,
// we will never reach a shorter distance
func (pdfa *ParametricDFA) isPrefixSink(state ParametricState, queryLen uint32) bool {
if state.isDeadEnd() {
return true
}
remOffset := queryLen - state.offset
if remOffset < pdfa.diameter {
stateDistances := pdfa.distance[pdfa.diameter*state.shapeID:]
prefixDistance := stateDistances[remOffset]
if prefixDistance > pdfa.maxDistance {
return false
}
for _, d := range stateDistances {
if d < prefixDistance {
return false
}
}
return true
}
return false
}
func (pdfa *ParametricDFA) numStates() int {
return len(pdfa.transitions) / int(pdfa.transitionStride)
}
func min(x, y uint32) uint32 {
if x < y {
return x
}
return y
}
func (pdfa *ParametricDFA) transition(state ParametricState,
chi uint32) Transition {
return pdfa.transitions[pdfa.transitionStride*state.shapeID+chi]
}
func (pdfa *ParametricDFA) getDistance(state ParametricState,
qLen uint32) Distance {
remainingOffset := qLen - state.offset
if state.isDeadEnd() || remainingOffset >= pdfa.diameter {
return Atleast{d: pdfa.maxDistance + 1}
}
dist := pdfa.distance[int(pdfa.diameter*state.shapeID)+int(remainingOffset)]
if dist > pdfa.maxDistance {
return Atleast{d: dist}
}
return Exact{d: dist}
}
func (pdfa *ParametricDFA) computeDistance(left, right string) Distance {
state := pdfa.initialState()
leftChars := []rune(left)
for _, chr := range []rune(right) {
start := state.offset
stop := min(start+pdfa.diameter, uint32(len(leftChars)))
chi := characteristicVector(leftChars[start:stop], chr)
transition := pdfa.transition(state, uint32(chi))
state = transition.apply(state)
if state.isDeadEnd() {
return Atleast{d: pdfa.maxDistance + 1}
}
}
return pdfa.getDistance(state, uint32(len(left)))
}
func (pdfa *ParametricDFA) buildDfa(query string, distance uint8,
prefix bool) (*DFA, error) {
qLen := uint32(len([]rune(query)))
alphabet := queryChars(query)
psi := newParametricStateIndex(qLen, uint32(pdfa.numStates()))
maxNumStates := psi.maxNumStates()
deadEndStateID := psi.getOrAllocate(newParametricState())
if deadEndStateID != 0 {
return nil, fmt.Errorf("Invalid dead end state")
}
initialStateID := psi.getOrAllocate(pdfa.initialState())
dfaBuilder := withMaxStates(uint32(maxNumStates))
mask := uint32((1 << pdfa.diameter) - 1)
var stateID int
for stateID = 0; stateID < StateLimit; stateID++ {
if stateID == psi.numStates() {
break
}
state := psi.get(uint32(stateID))
if prefix && pdfa.isPrefixSink(state, qLen) {
distance := pdfa.getDistance(state, qLen)
dfaBuilder.addState(uint32(stateID), uint32(stateID), distance)
} else {
transition := pdfa.transition(state, 0)
defSuccessor := transition.apply(state)
defSuccessorID := psi.getOrAllocate(defSuccessor)
distance := pdfa.getDistance(state, qLen)
stateBuilder, err := dfaBuilder.addState(uint32(stateID), defSuccessorID, distance)
if err != nil {
return nil, fmt.Errorf("parametric_dfa: buildDfa, err: %v", err)
}
alphabet.resetNext()
chr, cv, err := alphabet.next()
for err == nil {
chi := cv.shiftAndMask(state.offset, mask)
transition := pdfa.transition(state, chi)
destState := transition.apply(state)
destStateID := psi.getOrAllocate(destState)
stateBuilder.addTransition(chr, destStateID)
chr, cv, err = alphabet.next()
}
}
}
if stateID == StateLimit {
return nil, ErrTooManyStates
}
dfaBuilder.setInitialState(initialStateID)
return dfaBuilder.build(distance), nil
}
func fromNfa(nfa *LevenshteinNFA) (*ParametricDFA, error) {
lookUp := newHash()
lookUp.getOrAllocate(*newMultiState())
initialState := nfa.initialStates()
lookUp.getOrAllocate(*initialState)
maxDistance := nfa.maxDistance()
msDiameter := nfa.msDiameter()
numChi := 1 << msDiameter
chiValues := make([]uint64, numChi)
for i := 0; i < numChi; i++ {
chiValues[i] = uint64(i)
}
transitions := make([]Transition, 0, numChi*int(msDiameter))
var stateID int
for stateID = 0; stateID < StateLimit; stateID++ {
if stateID == len(lookUp.items) {
break
}
for _, chi := range chiValues {
destMs := newMultiState()
ms := lookUp.getFromID(stateID)
nfa.transition(ms, destMs, chi)
translation := destMs.normalize()
destID := lookUp.getOrAllocate(*destMs)
transitions = append(transitions, Transition{
destShapeID: uint32(destID),
deltaOffset: translation,
})
}
}
if stateID == StateLimit {
return nil, ErrTooManyStates
}
ns := len(lookUp.items)
diameter := int(msDiameter)
distances := make([]uint8, 0, diameter*ns)
for stateID := 0; stateID < ns; stateID++ {
ms := lookUp.getFromID(stateID)
for offset := 0; offset < diameter; offset++ {
dist := nfa.multistateDistance(ms, uint32(offset))
distances = append(distances, dist.distance())
}
}
return &ParametricDFA{
diameter: uint32(msDiameter),
transitions: transitions,
maxDistance: maxDistance,
transitionStride: uint32(numChi),
distance: distances,
}, nil
}
type hash struct {
index map[[16]byte]int
items []MultiState
}
func newHash() *hash {
return &hash{
index: make(map[[16]byte]int, 100),
items: make([]MultiState, 0, 100),
}
}
func (h *hash) getOrAllocate(m MultiState) int {
size := len(h.items)
var exists bool
var pos int
md5 := getHash(&m)
if pos, exists = h.index[md5]; !exists {
h.index[md5] = size
pos = size
h.items = append(h.items, m)
}
return pos
}
func (h *hash) getFromID(id int) *MultiState {
return &h.items[id]
}
func getHash(ms *MultiState) [16]byte {
msBytes := []byte{}
for _, state := range ms.states {
jsonBytes, _ := json.Marshal(&state)
msBytes = append(msBytes, jsonBytes...)
}
return md5.Sum(msBytes)
}