Revise ranking algorithm

CHANGELOG.md

@@ -1,6 +1,13 @@
 CHANGELOG
 =========
 
+0.15.0
+------
+- Improved fuzzy search algorithm
+    - Added `--algo=[v1|v2]` option so one can still choose the old algorithm
+      which values the search performance over the quality of the result
+- Advanced scoring criteria
+
 0.13.5
 ------
 - Memory and performance optimization

install

@@ -2,8 +2,8 @@
 
 set -u
 
-[[ "$@" =~ --pre ]] && version=0.13.5 pre=1 ||
+[[ "$@" =~ --pre ]] && version=0.15.0 pre=1 ||
-                       version=0.13.5 pre=0
+                       version=0.15.0 pre=0
 
 auto_completion=
 key_bindings=

man/man1/fzf-tmux.1

@@ -21,7 +21,7 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ..
-.TH fzf-tmux 1 "Aug 2016" "fzf 0.13.5" "fzf-tmux - open fzf in tmux split pane"
+.TH fzf-tmux 1 "Sep 2016" "fzf 0.15.0" "fzf-tmux - open fzf in tmux split pane"
 
 .SH NAME
 fzf-tmux - open fzf in tmux split pane

man/man1/fzf.1

@@ -21,7 +21,7 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ..
-.TH fzf 1 "Aug 2016" "fzf 0.13.5" "fzf - a command-line fuzzy finder"
+.TH fzf 1 "Sep 2016" "fzf 0.15.0" "fzf - a command-line fuzzy finder"
 
 .SH NAME
 fzf - a command-line fuzzy finder
@@ -47,6 +47,16 @@ Case-insensitive match (default: smart-case match)
 .TP
 .B "+i"
 Case-sensitive match
+.TP
+.BI "--algo=" TYPE
+Fuzzy matching algorithm (default: v2)
+
+.br
+.BR v2 "     Optimal scoring algorithm (quality)"
+.br
+.BR v1 "     Faster but not guaranteed to find the optimal result (performance)"
+.br
+
 .TP
 .BI "-n, --nth=" "N[,..]"
 Comma-separated list of field index expressions for limiting search scope.

src/README.md

@@ -61,6 +61,23 @@ make install
 make linux
 ```
 
+Test
+----
+
+Unit tests can be run with `make test`. Integration tests are written in Ruby
+script that should be run on tmux.
+
+```sh
+# Unit tests
+make test
+
+# Install the executable to ../bin directory
+make install
+
+# Integration tests
+ruby ../test/test_go.rb
+```
+
 Third-party libraries used
 --------------------------
 

src/algo/algo.go

@@ -1,19 +1,91 @@
 package algo
 
+/*
+
+Algorithm
+---------
+
+FuzzyMatchV1 finds the first "fuzzy" occurrence of the pattern within the given
+text in O(n) time where n is the length of the text. Once the position of the
+last character is located, it traverses backwards to see if there's a shorter
+substring that matches the pattern.
+
+    a_____b___abc__  To find "abc"
+    *-----*-----*>   1. Forward scan
+             <***    2. Backward scan
+
+The algorithm is simple and fast, but as it only sees the first occurrence,
+it is not guaranteed to find the occurrence with the highest score.
+
+    a_____b__c__abc
+    *-----*--*  ***
+
+FuzzyMatchV2 implements a modified version of Smith-Waterman algorithm to find
+the optimal solution (highest score) according to the scoring criteria. Unlike
+the original algorithm, omission or mismatch of a character in the pattern is
+not allowed.
+
+Performance
+-----------
+
+The new V2 algorithm is slower than V1 as it examines all occurrences of the
+pattern instead of stopping immediately after finding the first one. The time
+complexity of the algorithm is O(nm) if a match is found and O(n) otherwise
+where n is the length of the item and m is the length of the pattern. Thus, the
+performance overhead may not be noticeable for a query with high selectivity.
+However, if the performance is more important than the quality of the result,
+you can still choose v1 algorithm with --algo=v1.
+
+Scoring criteria
+----------------
+
+- We prefer matches at special positions, such as the start of a word, or
+  uppercase character in camelCase words.
+
+- That is, we prefer an occurrence of the pattern with more characters
+  matching at special positions, even if the total match length is longer.
+    e.g. "fuzzyfinder" vs. "fuzzy-finder" on "ff"
+                            ````````````
+- Also, if the first character in the pattern appears at one of the special
+  positions, the bonus point for the position is multiplied by a constant
+  as it is extremely likely that the first character in the typed pattern
+  has more significance than the rest.
+    e.g. "fo-bar" vs. "foob-r" on "br"
+          ``````
+- But since fzf is still a fuzzy finder, not an acronym finder, we should also
+  consider the total length of the matched substring. This is why we have the
+  gap penalty. The gap penalty increases as the length of the gap (distance
+  between the matching characters) increases, so the effect of the bonus is
+  eventually cancelled at some point.
+    e.g. "fuzzyfinder" vs. "fuzzy-blurry-finder" on "ff"
+          ```````````
+- Consequently, it is crucial to find the right balance between the bonus
+  and the gap penalty. The parameters were chosen that the bonus is cancelled
+  when the gap size increases beyond 8 characters.
+
+- The bonus mechanism can have the undesirable side effect where consecutive
+  matches are ranked lower than the ones with gaps.
+    e.g. "foobar" vs. "foo-bar" on "foob"
+                       ```````
+- To correct this anomaly, we also give extra bonus point to each character
+  in a consecutive matching chunk.
+    e.g. "foobar" vs. "foo-bar" on "foob"
+          ``````
+- The amount of consecutive bonus is primarily determined by the bonus of the
+  first character in the chunk.
+    e.g. "foobar" vs. "out-of-bound" on "oob"
+                       ````````````
+*/
+
 import (
+	"fmt"
 	"strings"
 	"unicode"
 
 	"github.com/junegunn/fzf/src/util"
 )
 
-/*
+var DEBUG bool
- * String matching algorithms here do not use strings.ToLower to avoid
- * performance penalty. And they assume pattern runes are given in lowercase
- * letters when caseSensitive is false.
- *
- * In short: They try to do as little work as possible.
- */
 
 func indexAt(index int, max int, forward bool) int {
 	if forward {
@@ -24,14 +96,48 @@ func indexAt(index int, max int, forward bool) int {
 
 // Result contains the results of running a match function.
 type Result struct {
+	// TODO int32 should suffice
 	Start int
 	End   int
-
+	Score int
-	// Items are basically sorted by the lengths of matched substrings.
-	// But we slightly adjust the score with bonus for better results.
-	Bonus int
 }
 
+const (
+	scoreMatch        = 16
+	scoreGapStart     = -3
+	scoreGapExtention = -1
+
+	// We prefer matches at the beginning of a word, but the bonus should not be
+	// too great to prevent the longer acronym matches from always winning over
+	// shorter fuzzy matches. The bonus point here was specifically chosen that
+	// the bonus is cancelled when the gap between the acronyms grows over
+	// 8 characters, which is approximately the average length of the words found
+	// in web2 dictionary and my file system.
+	bonusBoundary = scoreMatch / 2
+
+	// Although bonus point for non-word characters is non-contextual, we need it
+	// for computing bonus points for consecutive chunks starting with a non-word
+	// character.
+	bonusNonWord = scoreMatch / 2
+
+	// Edge-triggered bonus for matches in camelCase words.
+	// Compared to word-boundary case, they don't accompany single-character gaps
+	// (e.g. FooBar vs. foo-bar), so we deduct bonus point accordingly.
+	bonusCamel123 = bonusBoundary + scoreGapExtention
+
+	// Minimum bonus point given to characters in consecutive chunks.
+	// Note that bonus points for consecutive matches shouldn't have needed if we
+	// used fixed match score as in the original algorithm.
+	bonusConsecutive = -(scoreGapStart + scoreGapExtention)
+
+	// The first character in the typed pattern usually has more significance
+	// than the rest so it's important that it appears at special positions where
+	// bonus points are given. e.g. "to-go" vs. "ongoing" on "og" or on "ogo".
+	// The amount of the extra bonus should be limited so that the gap penalty is
+	// still respected.
+	bonusFirstCharMultiplier = 2
+)
+
 type charClass int
 
 const (
@@ -42,39 +148,299 @@ const (
 	charNumber
 )
 
-func evaluateBonus(caseSensitive bool, text util.Chars, pattern []rune, sidx int, eidx int) int {
+func posArray(withPos bool, len int) *[]int {
-	var bonus int
+	if withPos {
-	pidx := 0
+		pos := make([]int, 0, len)
-	lenPattern := len(pattern)
+		return &pos
-	consecutive := false
+	}
-	prevClass := charNonWord
+	return nil
-	for index := util.Max(0, sidx-1); index < eidx; index++ {
-		char := text.Get(index)
-		var class charClass
-		if unicode.IsLower(char) {
-			class = charLower
-		} else if unicode.IsUpper(char) {
-			class = charUpper
-		} else if unicode.IsLetter(char) {
-			class = charLetter
-		} else if unicode.IsNumber(char) {
-			class = charNumber
-		} else {
-			class = charNonWord
 }
 
-		var point int
+func alloc16(offset int, slab *util.Slab, size int, clear bool) (int, []int16) {
+	if slab != nil && cap(slab.I16) > offset+size {
+		slice := slab.I16[offset : offset+size]
+		if clear {
+			for idx := range slice {
+				slice[idx] = 0
+			}
+		}
+		return offset + size, slice
+	}
+	return offset, make([]int16, size)
+}
+
+func alloc32(offset int, slab *util.Slab, size int, clear bool) (int, []int32) {
+	if slab != nil && cap(slab.I32) > offset+size {
+		slice := slab.I32[offset : offset+size]
+		if clear {
+			for idx := range slice {
+				slice[idx] = 0
+			}
+		}
+		return offset + size, slice
+	}
+	return offset, make([]int32, size)
+}
+
+func charClassOfAscii(char rune) charClass {
+	if char >= 'a' && char <= 'z' {
+		return charLower
+	} else if char >= 'A' && char <= 'Z' {
+		return charUpper
+	} else if char >= '0' && char <= '9' {
+		return charNumber
+	}
+	return charNonWord
+}
+
+func charClassOfNonAscii(char rune) charClass {
+	if unicode.IsLower(char) {
+		return charLower
+	} else if unicode.IsUpper(char) {
+		return charUpper
+	} else if unicode.IsNumber(char) {
+		return charNumber
+	} else if unicode.IsLetter(char) {
+		return charLetter
+	}
+	return charNonWord
+}
+
+func charClassOf(char rune) charClass {
+	if char <= unicode.MaxASCII {
+		return charClassOfAscii(char)
+	}
+	return charClassOfNonAscii(char)
+}
+
+func bonusFor(prevClass charClass, class charClass) int16 {
 	if prevClass == charNonWord && class != charNonWord {
 		// Word boundary
-			point = 2
+		return bonusBoundary
 	} else if prevClass == charLower && class == charUpper ||
 		prevClass != charNumber && class == charNumber {
 		// camelCase letter123
-			point = 1
+		return bonusCamel123
+	} else if class == charNonWord {
+		return bonusNonWord
 	}
+	return 0
+}
+
+func bonusAt(input util.Chars, idx int) int16 {
+	if idx == 0 {
+		return bonusBoundary
+	}
+	return bonusFor(charClassOf(input.Get(idx-1)), charClassOf(input.Get(idx)))
+}
+
+type Algo func(caseSensitive bool, forward bool, input util.Chars, pattern []rune, withPos bool, slab *util.Slab) (Result, *[]int)
+
+func FuzzyMatchV2(caseSensitive bool, forward bool, input util.Chars, pattern []rune, withPos bool, slab *util.Slab) (Result, *[]int) {
+	// Assume that pattern is given in lowercase if case-insensitive.
+	// First check if there's a match and calculate bonus for each position.
+	// If the input string is too long, consider finding the matching chars in
+	// this phase as well (non-optimal alignment).
+	N := input.Length()
+	M := len(pattern)
+	switch M {
+	case 0:
+		return Result{0, 0, 0}, posArray(withPos, M)
+	case 1:
+		return ExactMatchNaive(caseSensitive, forward, input, pattern[0:1], withPos, slab)
+	}
+
+	// Since O(nm) algorithm can be prohibitively expensive for large input,
+	// we fall back to the greedy algorithm.
+	if slab != nil && N*M > cap(slab.I16) {
+		return FuzzyMatchV1(caseSensitive, forward, input, pattern, withPos, slab)
+	}
+
+	// Reuse pre-allocated integer slice to avoid unnecessary sweeping of garbages
+	offset := 0
+	// Bonus point for each position
+	offset, B := alloc16(offset, slab, N, false)
+	// The first occurrence of each character in the pattern
+	offset, F := alloc16(offset, slab, M, false)
+	// Rune array
+	_, T := alloc32(0, slab, N, false)
+
+	// Phase 1. Check if there's a match and calculate bonus for each point
+	pidx, lastIdx, prevClass := 0, 0, charNonWord
+	for idx := 0; idx < N; idx++ {
+		char := input.Get(idx)
+		var class charClass
+		if char <= unicode.MaxASCII {
+			class = charClassOfAscii(char)
+		} else {
+			class = charClassOfNonAscii(char)
+		}
+
+		if !caseSensitive && class == charUpper {
+			if char <= unicode.MaxASCII {
+				char += 32
+			} else {
+				char = unicode.To(unicode.LowerCase, char)
+			}
+		}
+
+		T[idx] = char
+		B[idx] = bonusFor(prevClass, class)
 		prevClass = class
 
-		if index >= sidx {
+		if pidx < M {
+			if char == pattern[pidx] {
+				lastIdx = idx
+				F[pidx] = int16(idx)
+				pidx++
+			}
+		} else {
+			if char == pattern[M-1] {
+				lastIdx = idx
+			}
+		}
+	}
+	if pidx != M {
+		return Result{-1, -1, 0}, nil
+	}
+
+	// Phase 2. Fill in score matrix (H)
+	// Unlike the original algorithm, we do not allow omission.
+	width := lastIdx - int(F[0]) + 1
+	offset, H := alloc16(offset, slab, width*M, false)
+
+	// Possible length of consecutive chunk at each position.
+	offset, C := alloc16(offset, slab, width*M, false)
+
+	maxScore, maxScorePos := int16(0), 0
+	for i := 0; i < M; i++ {
+		I := i * width
+		inGap := false
+		for j := int(F[i]); j <= lastIdx; j++ {
+			j0 := j - int(F[0])
+			var s1, s2, consecutive int16
+
+			if j > int(F[i]) {
+				if inGap {
+					s2 = H[I+j0-1] + scoreGapExtention
+				} else {
+					s2 = H[I+j0-1] + scoreGapStart
+				}
+			}
+
+			if pattern[i] == T[j] {
+				var diag int16
+				if i > 0 && j0 > 0 {
+					diag = H[I-width+j0-1]
+				}
+				s1 = diag + scoreMatch
+				b := B[j]
+				if i > 0 {
+					// j > 0 if i > 0
+					consecutive = C[I-width+j0-1] + 1
+					// Break consecutive chunk
+					if b == bonusBoundary {
+						consecutive = 1
+					} else if consecutive > 1 {
+						b = util.Max16(b, util.Max16(bonusConsecutive, B[j-int(consecutive)+1]))
+					}
+				} else {
+					consecutive = 1
+					b *= bonusFirstCharMultiplier
+				}
+				if s1+b < s2 {
+					s1 += B[j]
+					consecutive = 0
+				} else {
+					s1 += b
+				}
+			}
+			C[I+j0] = consecutive
+
+			inGap = s1 < s2
+			score := util.Max16(util.Max16(s1, s2), 0)
+			if i == M-1 && (forward && score > maxScore || !forward && score >= maxScore) {
+				maxScore, maxScorePos = score, j
+			}
+			H[I+j0] = score
+		}
+
+		if DEBUG {
+			if i == 0 {
+				fmt.Print("  ")
+				for j := int(F[i]); j <= lastIdx; j++ {
+					fmt.Printf(" " + string(input.Get(j)) + " ")
+				}
+				fmt.Println()
+			}
+			fmt.Print(string(pattern[i]) + " ")
+			for idx := int(F[0]); idx < int(F[i]); idx++ {
+				fmt.Print(" 0 ")
+			}
+			for idx := int(F[i]); idx <= lastIdx; idx++ {
+				fmt.Printf("%2d ", H[i*width+idx-int(F[0])])
+			}
+			fmt.Println()
+
+			fmt.Print("  ")
+			for idx, p := range C[I : I+width] {
+				if idx+int(F[0]) < int(F[i]) {
+					p = 0
+				}
+				fmt.Printf("%2d ", p)
+			}
+			fmt.Println()
+		}
+	}
+
+	// Phase 3. (Optional) Backtrace to find character positions
+	pos := posArray(withPos, M)
+	j := int(F[0])
+	if withPos {
+		i := M - 1
+		j = maxScorePos
+		preferMatch := true
+		for {
+			I := i * width
+			j0 := j - int(F[0])
+			s := H[I+j0]
+
+			var s1, s2 int16
+			if i > 0 && j >= int(F[i]) {
+				s1 = H[I-width+j0-1]
+			}
+			if j > int(F[i]) {
+				s2 = H[I+j0-1]
+			}
+
+			if s > s1 && (s > s2 || s == s2 && preferMatch) {
+				*pos = append(*pos, j)
+				if i == 0 {
+					break
+				}
+				i--
+			}
+			preferMatch = C[I+j0] > 1 || I+width+j0+1 < len(C) && C[I+width+j0+1] > 0
+			j--
+		}
+	}
+	// Start offset we return here is only relevant when begin tiebreak is used.
+	// However finding the accurate offset requires backtracking, and we don't
+	// want to pay extra cost for the option that has lost its importance.
+	return Result{j, maxScorePos + 1, int(maxScore)}, pos
+}
+
+// Implement the same sorting criteria as V2
+func calculateScore(caseSensitive bool, text util.Chars, pattern []rune, sidx int, eidx int, withPos bool) (int, *[]int) {
+	pidx, score, inGap, consecutive, firstBonus := 0, 0, false, 0, int16(0)
+	pos := posArray(withPos, len(pattern))
+	prevClass := charNonWord
+	if sidx > 0 {
+		prevClass = charClassOf(text.Get(sidx - 1))
+	}
+	for idx := sidx; idx < eidx; idx++ {
+		char := text.Get(idx)
+		class := charClassOf(char)
 		if !caseSensitive {
 			if char >= 'A' && char <= 'Z' {
 				char += 32
@@ -82,45 +448,50 @@ func evaluateBonus(caseSensitive bool, text util.Chars, pattern []rune, sidx int
 				char = unicode.To(unicode.LowerCase, char)
 			}
 		}
-			pchar := pattern[pidx]
+		if char == pattern[pidx] {
-			if pchar == char {
+			if withPos {
-				// Boost bonus for the first character in the pattern
+				*pos = append(*pos, idx)
-				if pidx == 0 {
-					point *= 2
 			}
-				// Bonus to consecutive matching chars
+			score += scoreMatch
-				if consecutive {
+			bonus := bonusFor(prevClass, class)
-					point++
+			if consecutive == 0 {
-				}
+				firstBonus = bonus
-				bonus += point
-
-				if pidx++; pidx == lenPattern {
-					break
-				}
-				consecutive = true
 			} else {
-				consecutive = false
+				// Break consecutive chunk
+				if bonus == bonusBoundary {
+					firstBonus = bonus
 				}
+				bonus = util.Max16(util.Max16(bonus, firstBonus), bonusConsecutive)
 			}
+			if pidx == 0 {
+				score += int(bonus * bonusFirstCharMultiplier)
+			} else {
+				score += int(bonus)
 			}
-	return bonus
+			inGap = false
+			consecutive++
+			pidx++
+		} else {
+			if inGap {
+				score += scoreGapExtention
+			} else {
+				score += scoreGapStart
+			}
+			inGap = true
+			consecutive = 0
+			firstBonus = 0
+		}
+		prevClass = class
+	}
+	return score, pos
 }
 
-// FuzzyMatch performs fuzzy-match
+// FuzzyMatchV1 performs fuzzy-match
-func FuzzyMatch(caseSensitive bool, forward bool, text util.Chars, pattern []rune) Result {
+func FuzzyMatchV1(caseSensitive bool, forward bool, text util.Chars, pattern []rune, withPos bool, slab *util.Slab) (Result, *[]int) {
 	if len(pattern) == 0 {
-		return Result{0, 0, 0}
+		return Result{0, 0, 0}, nil
 	}
 
-	// 0. (FIXME) How to find the shortest match?
-	//    a_____b__c__abc
-	//    ^^^^^^^^^^  ^^^
-	// 1. forward scan (abc)
-	//   *-----*-----*>
-	//   a_____b___abc__
-	// 2. reverse scan (cba)
-	//   a_____b___abc__
-	//            <***
 	pidx := 0
 	sidx := -1
 	eidx := -1
@@ -157,7 +528,8 @@ func FuzzyMatch(caseSensitive bool, forward bool, text util.Chars, pattern []run
 	if sidx >= 0 && eidx >= 0 {
 		pidx--
 		for index := eidx - 1; index >= sidx; index-- {
-			char := text.Get(indexAt(index, lenRunes, forward))
+			tidx := indexAt(index, lenRunes, forward)
+			char := text.Get(tidx)
 			if !caseSensitive {
 				if char >= 'A' && char <= 'Z' {
 					char += 32
@@ -166,7 +538,8 @@ func FuzzyMatch(caseSensitive bool, forward bool, text util.Chars, pattern []run
 				}
 			}
 
-			pchar := pattern[indexAt(pidx, lenPattern, forward)]
+			pidx_ := indexAt(pidx, lenPattern, forward)
+			pchar := pattern[pidx_]
 			if char == pchar {
 				if pidx--; pidx < 0 {
 					sidx = index
@@ -175,16 +548,14 @@ func FuzzyMatch(caseSensitive bool, forward bool, text util.Chars, pattern []run
 			}
 		}
 
-		// Calculate the bonus. This can't be done at the same time as the
-		// pattern scan above because 'forward' may be false.
 		if !forward {
 			sidx, eidx = lenRunes-eidx, lenRunes-sidx
 		}
 
-		return Result{sidx, eidx,
+		score, pos := calculateScore(caseSensitive, text, pattern, sidx, eidx, withPos)
-			evaluateBonus(caseSensitive, text, pattern, sidx, eidx)}
+		return Result{sidx, eidx, score}, pos
 	}
-	return Result{-1, -1, 0}
+	return Result{-1, -1, 0}, nil
 }
 
 // ExactMatchNaive is a basic string searching algorithm that handles case
@@ -192,23 +563,28 @@ func FuzzyMatch(caseSensitive bool, forward bool, text util.Chars, pattern []run
 // of strings.ToLower + strings.Index for typical fzf use cases where input
 // strings and patterns are not very long.
 //
-// We might try to implement better algorithms in the future:
+// Since 0.15.0, this function searches for the match with the highest
-// http://en.wikipedia.org/wiki/String_searching_algorithm
+// bonus point, instead of stopping immediately after finding the first match.
-func ExactMatchNaive(caseSensitive bool, forward bool, text util.Chars, pattern []rune) Result {
+// The solution is much cheaper since there is only one possible alignment of
+// the pattern.
+func ExactMatchNaive(caseSensitive bool, forward bool, text util.Chars, pattern []rune, withPos bool, slab *util.Slab) (Result, *[]int) {
 	if len(pattern) == 0 {
-		return Result{0, 0, 0}
+		return Result{0, 0, 0}, nil
 	}
 
 	lenRunes := text.Length()
 	lenPattern := len(pattern)
 
 	if lenRunes < lenPattern {
-		return Result{-1, -1, 0}
+		return Result{-1, -1, 0}, nil
 	}
 
+	// For simplicity, only look at the bonus at the first character position
 	pidx := 0
+	bestPos, bonus, bestBonus := -1, int16(0), int16(-1)
 	for index := 0; index < lenRunes; index++ {
-		char := text.Get(indexAt(index, lenRunes, forward))
+		index_ := indexAt(index, lenRunes, forward)
+		char := text.Get(index_)
 		if !caseSensitive {
 			if char >= 'A' && char <= 'Z' {
 				char += 32
@@ -216,33 +592,51 @@ func ExactMatchNaive(caseSensitive bool, forward bool, text util.Chars, pattern
 				char = unicode.To(unicode.LowerCase, char)
 			}
 		}
-		pchar := pattern[indexAt(pidx, lenPattern, forward)]
+		pidx_ := indexAt(pidx, lenPattern, forward)
+		pchar := pattern[pidx_]
 		if pchar == char {
+			if pidx_ == 0 {
+				bonus = bonusAt(text, index_)
+			}
 			pidx++
 			if pidx == lenPattern {
-				var sidx, eidx int
+				if bonus > bestBonus {
-				if forward {
+					bestPos, bestBonus = index, bonus
-					sidx = index - lenPattern + 1
-					eidx = index + 1
-				} else {
-					sidx = lenRunes - (index + 1)
-					eidx = lenRunes - (index - lenPattern + 1)
 				}
-				return Result{sidx, eidx,
+				if bonus == bonusBoundary {
-					evaluateBonus(caseSensitive, text, pattern, sidx, eidx)}
+					break
+				}
+				index -= pidx - 1
+				pidx, bonus = 0, 0
 			}
 		} else {
 			index -= pidx
-			pidx = 0
+			pidx, bonus = 0, 0
 		}
 	}
-	return Result{-1, -1, 0}
+	if bestPos >= 0 {
+		var sidx, eidx int
+		if forward {
+			sidx = bestPos - lenPattern + 1
+			eidx = bestPos + 1
+		} else {
+			sidx = lenRunes - (bestPos + 1)
+			eidx = lenRunes - (bestPos - lenPattern + 1)
+		}
+		score, _ := calculateScore(caseSensitive, text, pattern, sidx, eidx, false)
+		return Result{sidx, eidx, score}, nil
+	}
+	return Result{-1, -1, 0}, nil
 }
 
 // PrefixMatch performs prefix-match
-func PrefixMatch(caseSensitive bool, forward bool, text util.Chars, pattern []rune) Result {
+func PrefixMatch(caseSensitive bool, forward bool, text util.Chars, pattern []rune, withPos bool, slab *util.Slab) (Result, *[]int) {
+	if len(pattern) == 0 {
+		return Result{0, 0, 0}, nil
+	}
+
 	if text.Length() < len(pattern) {
-		return Result{-1, -1, 0}
+		return Result{-1, -1, 0}, nil
 	}
 
 	for index, r := range pattern {
@@ -251,20 +645,24 @@ func PrefixMatch(caseSensitive bool, forward bool, text util.Chars, pattern []ru
 			char = unicode.ToLower(char)
 		}
 		if char != r {
-			return Result{-1, -1, 0}
+			return Result{-1, -1, 0}, nil
 		}
 	}
 	lenPattern := len(pattern)
-	return Result{0, lenPattern,
+	score, _ := calculateScore(caseSensitive, text, pattern, 0, lenPattern, false)
-		evaluateBonus(caseSensitive, text, pattern, 0, lenPattern)}
+	return Result{0, lenPattern, score}, nil
 }
 
 // SuffixMatch performs suffix-match
-func SuffixMatch(caseSensitive bool, forward bool, text util.Chars, pattern []rune) Result {
+func SuffixMatch(caseSensitive bool, forward bool, text util.Chars, pattern []rune, withPos bool, slab *util.Slab) (Result, *[]int) {
-	trimmedLen := text.Length() - text.TrailingWhitespaces()
+	lenRunes := text.Length()
+	trimmedLen := lenRunes - text.TrailingWhitespaces()
+	if len(pattern) == 0 {
+		return Result{trimmedLen, trimmedLen, 0}, nil
+	}
 	diff := trimmedLen - len(pattern)
 	if diff < 0 {
-		return Result{-1, -1, 0}
+		return Result{-1, -1, 0}, nil
 	}
 
 	for index, r := range pattern {
@@ -273,28 +671,29 @@ func SuffixMatch(caseSensitive bool, forward bool, text util.Chars, pattern []ru
 			char = unicode.ToLower(char)
 		}
 		if char != r {
-			return Result{-1, -1, 0}
+			return Result{-1, -1, 0}, nil
 		}
 	}
 	lenPattern := len(pattern)
 	sidx := trimmedLen - lenPattern
 	eidx := trimmedLen
-	return Result{sidx, eidx,
+	score, _ := calculateScore(caseSensitive, text, pattern, sidx, eidx, false)
-		evaluateBonus(caseSensitive, text, pattern, sidx, eidx)}
+	return Result{sidx, eidx, score}, nil
 }
 
 // EqualMatch performs equal-match
-func EqualMatch(caseSensitive bool, forward bool, text util.Chars, pattern []rune) Result {
+func EqualMatch(caseSensitive bool, forward bool, text util.Chars, pattern []rune, withPos bool, slab *util.Slab) (Result, *[]int) {
-	// Note: EqualMatch always return a zero bonus.
+	lenPattern := len(pattern)
-	if text.Length() != len(pattern) {
+	if text.Length() != lenPattern {
-		return Result{-1, -1, 0}
+		return Result{-1, -1, 0}, nil
 	}
 	runesStr := text.ToString()
 	if !caseSensitive {
 		runesStr = strings.ToLower(runesStr)
 	}
 	if runesStr == string(pattern) {
-		return Result{0, len(pattern), 0}
+		return Result{0, lenPattern, (scoreMatch+bonusBoundary)*lenPattern +
+			(bonusFirstCharMultiplier-1)*bonusBoundary}, nil
 	}
-	return Result{-1, -1, 0}
+	return Result{-1, -1, 0}, nil
 }

src/algo/algo_test.go

@@ -1,95 +1,154 @@
 package algo
 
 import (
+	"sort"
 	"strings"
 	"testing"
 
 	"github.com/junegunn/fzf/src/util"
 )
 
-func assertMatch(t *testing.T, fun func(bool, bool, util.Chars, []rune) Result, caseSensitive, forward bool, input, pattern string, sidx int, eidx int, bonus int) {
+func assertMatch(t *testing.T, fun Algo, caseSensitive, forward bool, input, pattern string, sidx int, eidx int, score int) {
 	if !caseSensitive {
 		pattern = strings.ToLower(pattern)
 	}
-	res := fun(caseSensitive, forward, util.RunesToChars([]rune(input)), []rune(pattern))
+	res, pos := fun(caseSensitive, forward, util.RunesToChars([]rune(input)), []rune(pattern), true, nil)
-	if res.Start != sidx {
+	var start, end int
-		t.Errorf("Invalid start index: %d (expected: %d, %s / %s)", res.Start, sidx, input, pattern)
+	if pos == nil || len(*pos) == 0 {
+		start = res.Start
+		end = res.End
+	} else {
+		sort.Ints(*pos)
+		start = (*pos)[0]
+		end = (*pos)[len(*pos)-1] + 1
 	}
-	if res.End != eidx {
+	if start != sidx {
-		t.Errorf("Invalid end index: %d (expected: %d, %s / %s)", res.End, eidx, input, pattern)
+		t.Errorf("Invalid start index: %d (expected: %d, %s / %s)", start, sidx, input, pattern)
 	}
-	if res.Bonus != bonus {
+	if end != eidx {
-		t.Errorf("Invalid bonus: %d (expected: %d, %s / %s)", res.Bonus, bonus, input, pattern)
+		t.Errorf("Invalid end index: %d (expected: %d, %s / %s)", end, eidx, input, pattern)
+	}
+	if res.Score != score {
+		t.Errorf("Invalid score: %d (expected: %d, %s / %s)", res.Score, score, input, pattern)
 	}
 }
 
 func TestFuzzyMatch(t *testing.T) {
-	assertMatch(t, FuzzyMatch, false, true, "fooBarbaz", "oBZ", 2, 9, 2)
+	for _, fn := range []Algo{FuzzyMatchV1, FuzzyMatchV2} {
-	assertMatch(t, FuzzyMatch, false, true, "foo bar baz", "fbb", 0, 9, 8)
+		for _, forward := range []bool{true, false} {
-	assertMatch(t, FuzzyMatch, false, true, "/AutomatorDocument.icns", "rdoc", 9, 13, 4)
+			assertMatch(t, fn, false, forward, "fooBarbaz1", "oBZ", 2, 9,
-	assertMatch(t, FuzzyMatch, false, true, "/man1/zshcompctl.1", "zshc", 6, 10, 7)
+				scoreMatch*3+bonusCamel123+scoreGapStart+scoreGapExtention*3)
-	assertMatch(t, FuzzyMatch, false, true, "/.oh-my-zsh/cache", "zshc", 8, 13, 8)
+			assertMatch(t, fn, false, forward, "foo bar baz", "fbb", 0, 9,
-	assertMatch(t, FuzzyMatch, false, true, "ab0123 456", "12356", 3, 10, 3)
+				scoreMatch*3+bonusBoundary*bonusFirstCharMultiplier+
-	assertMatch(t, FuzzyMatch, false, true, "abc123 456", "12356", 3, 10, 5)
+					bonusBoundary*2+2*scoreGapStart+4*scoreGapExtention)
+			assertMatch(t, fn, false, forward, "/AutomatorDocument.icns", "rdoc", 9, 13,
+				scoreMatch*4+bonusCamel123+bonusConsecutive*2)
+			assertMatch(t, fn, false, forward, "/man1/zshcompctl.1", "zshc", 6, 10,
+				scoreMatch*4+bonusBoundary*bonusFirstCharMultiplier+bonusBoundary*3)
+			assertMatch(t, fn, false, forward, "/.oh-my-zsh/cache", "zshc", 8, 13,
+				scoreMatch*4+bonusBoundary*bonusFirstCharMultiplier+bonusBoundary*3+scoreGapStart)
+			assertMatch(t, fn, false, forward, "ab0123 456", "12356", 3, 10,
+				scoreMatch*5+bonusConsecutive*3+scoreGapStart+scoreGapExtention)
+			assertMatch(t, fn, false, forward, "abc123 456", "12356", 3, 10,
+				scoreMatch*5+bonusCamel123*bonusFirstCharMultiplier+bonusCamel123*2+bonusConsecutive+scoreGapStart+scoreGapExtention)
+			assertMatch(t, fn, false, forward, "foo/bar/baz", "fbb", 0, 9,
+				scoreMatch*3+bonusBoundary*bonusFirstCharMultiplier+
+					bonusBoundary*2+2*scoreGapStart+4*scoreGapExtention)
+			assertMatch(t, fn, false, forward, "fooBarBaz", "fbb", 0, 7,
+				scoreMatch*3+bonusBoundary*bonusFirstCharMultiplier+
+					bonusCamel123*2+2*scoreGapStart+2*scoreGapExtention)
+			assertMatch(t, fn, false, forward, "foo barbaz", "fbb", 0, 8,
+				scoreMatch*3+bonusBoundary*bonusFirstCharMultiplier+bonusBoundary+
+					scoreGapStart*2+scoreGapExtention*3)
+			assertMatch(t, fn, false, forward, "fooBar Baz", "foob", 0, 4,
+				scoreMatch*4+bonusBoundary*bonusFirstCharMultiplier+bonusBoundary*3)
+			assertMatch(t, fn, false, forward, "xFoo-Bar Baz", "foo-b", 1, 6,
+				scoreMatch*5+bonusCamel123*bonusFirstCharMultiplier+bonusCamel123*2+
+					bonusNonWord+bonusBoundary)
 
-	assertMatch(t, FuzzyMatch, false, true, "foo/bar/baz", "fbb", 0, 9, 8)
+			assertMatch(t, fn, true, forward, "fooBarbaz", "oBz", 2, 9,
-	assertMatch(t, FuzzyMatch, false, true, "fooBarBaz", "fbb", 0, 7, 6)
+				scoreMatch*3+bonusCamel123+scoreGapStart+scoreGapExtention*3)
-	assertMatch(t, FuzzyMatch, false, true, "foo barbaz", "fbb", 0, 8, 6)
+			assertMatch(t, fn, true, forward, "Foo/Bar/Baz", "FBB", 0, 9,
-	assertMatch(t, FuzzyMatch, false, true, "fooBar Baz", "foob", 0, 4, 8)
+				scoreMatch*3+bonusBoundary*(bonusFirstCharMultiplier+2)+
-	assertMatch(t, FuzzyMatch, true, true, "fooBarbaz", "oBZ", -1, -1, 0)
+					scoreGapStart*2+scoreGapExtention*4)
-	assertMatch(t, FuzzyMatch, true, true, "fooBarbaz", "oBz", 2, 9, 2)
+			assertMatch(t, fn, true, forward, "FooBarBaz", "FBB", 0, 7,
-	assertMatch(t, FuzzyMatch, true, true, "Foo Bar Baz", "fbb", -1, -1, 0)
+				scoreMatch*3+bonusBoundary*bonusFirstCharMultiplier+bonusCamel123*2+
-	assertMatch(t, FuzzyMatch, true, true, "Foo/Bar/Baz", "FBB", 0, 9, 8)
+					scoreGapStart*2+scoreGapExtention*2)
-	assertMatch(t, FuzzyMatch, true, true, "FooBarBaz", "FBB", 0, 7, 6)
+			assertMatch(t, fn, true, forward, "FooBar Baz", "FooB", 0, 4,
-	assertMatch(t, FuzzyMatch, true, true, "foo BarBaz", "fBB", 0, 8, 7)
+				scoreMatch*4+bonusBoundary*bonusFirstCharMultiplier+bonusBoundary*2+
-	assertMatch(t, FuzzyMatch, true, true, "FooBar Baz", "FooB", 0, 4, 8)
+					util.Max(bonusCamel123, bonusBoundary))
-	assertMatch(t, FuzzyMatch, true, true, "fooBarbaz", "fooBarbazz", -1, -1, 0)
+
+			// Consecutive bonus updated
+			assertMatch(t, fn, true, forward, "foo-bar", "o-ba", 2, 6,
+				scoreMatch*4+bonusBoundary*3)
+
+			// Non-match
+			assertMatch(t, fn, true, forward, "fooBarbaz", "oBZ", -1, -1, 0)
+			assertMatch(t, fn, true, forward, "Foo Bar Baz", "fbb", -1, -1, 0)
+			assertMatch(t, fn, true, forward, "fooBarbaz", "fooBarbazz", -1, -1, 0)
+		}
+	}
 }
 
 func TestFuzzyMatchBackward(t *testing.T) {
-	assertMatch(t, FuzzyMatch, false, true, "foobar fb", "fb", 0, 4, 4)
+	assertMatch(t, FuzzyMatchV1, false, true, "foobar fb", "fb", 0, 4,
-	assertMatch(t, FuzzyMatch, false, false, "foobar fb", "fb", 7, 9, 5)
+		scoreMatch*2+bonusBoundary*bonusFirstCharMultiplier+
+			scoreGapStart+scoreGapExtention)
+	assertMatch(t, FuzzyMatchV1, false, false, "foobar fb", "fb", 7, 9,
+		scoreMatch*2+bonusBoundary*bonusFirstCharMultiplier+bonusBoundary)
 }
 
 func TestExactMatchNaive(t *testing.T) {
 	for _, dir := range []bool{true, false} {
-		assertMatch(t, ExactMatchNaive, false, dir, "fooBarbaz", "oBA", 2, 5, 3)
 		assertMatch(t, ExactMatchNaive, true, dir, "fooBarbaz", "oBA", -1, -1, 0)
 		assertMatch(t, ExactMatchNaive, true, dir, "fooBarbaz", "fooBarbazz", -1, -1, 0)
 
-		assertMatch(t, ExactMatchNaive, false, dir, "/AutomatorDocument.icns", "rdoc", 9, 13, 4)
+		assertMatch(t, ExactMatchNaive, false, dir, "fooBarbaz", "oBA", 2, 5,
-		assertMatch(t, ExactMatchNaive, false, dir, "/man1/zshcompctl.1", "zshc", 6, 10, 7)
+			scoreMatch*3+bonusCamel123+bonusConsecutive)
-		assertMatch(t, ExactMatchNaive, false, dir, "/.oh-my-zsh/cache", "zsh/c", 8, 13, 10)
+		assertMatch(t, ExactMatchNaive, false, dir, "/AutomatorDocument.icns", "rdoc", 9, 13,
+			scoreMatch*4+bonusCamel123+bonusConsecutive*2)
+		assertMatch(t, ExactMatchNaive, false, dir, "/man1/zshcompctl.1", "zshc", 6, 10,
+			scoreMatch*4+bonusBoundary*(bonusFirstCharMultiplier+3))
+		assertMatch(t, ExactMatchNaive, false, dir, "/.oh-my-zsh/cache", "zsh/c", 8, 13,
+			scoreMatch*5+bonusBoundary*(bonusFirstCharMultiplier+4))
 	}
 }
 
 func TestExactMatchNaiveBackward(t *testing.T) {
-	assertMatch(t, ExactMatchNaive, false, true, "foobar foob", "oo", 1, 3, 1)
+	assertMatch(t, ExactMatchNaive, false, true, "foobar foob", "oo", 1, 3,
-	assertMatch(t, ExactMatchNaive, false, false, "foobar foob", "oo", 8, 10, 1)
+		scoreMatch*2+bonusConsecutive)
+	assertMatch(t, ExactMatchNaive, false, false, "foobar foob", "oo", 8, 10,
+		scoreMatch*2+bonusConsecutive)
 }
 
 func TestPrefixMatch(t *testing.T) {
+	score := (scoreMatch+bonusBoundary)*3 + bonusBoundary*(bonusFirstCharMultiplier-1)
+
 	for _, dir := range []bool{true, false} {
 		assertMatch(t, PrefixMatch, true, dir, "fooBarbaz", "Foo", -1, -1, 0)
 		assertMatch(t, PrefixMatch, false, dir, "fooBarBaz", "baz", -1, -1, 0)
-		assertMatch(t, PrefixMatch, false, dir, "fooBarbaz", "Foo", 0, 3, 6)
+		assertMatch(t, PrefixMatch, false, dir, "fooBarbaz", "Foo", 0, 3, score)
-		assertMatch(t, PrefixMatch, false, dir, "foOBarBaZ", "foo", 0, 3, 7)
+		assertMatch(t, PrefixMatch, false, dir, "foOBarBaZ", "foo", 0, 3, score)
-		assertMatch(t, PrefixMatch, false, dir, "f-oBarbaz", "f-o", 0, 3, 8)
+		assertMatch(t, PrefixMatch, false, dir, "f-oBarbaz", "f-o", 0, 3, score)
 	}
 }
 
 func TestSuffixMatch(t *testing.T) {
 	for _, dir := range []bool{true, false} {
-		assertMatch(t, SuffixMatch, false, dir, "fooBarbaz", "Foo", -1, -1, 0)
-		assertMatch(t, SuffixMatch, false, dir, "fooBarbaz", "baz", 6, 9, 2)
-		assertMatch(t, SuffixMatch, false, dir, "fooBarBaZ", "baz", 6, 9, 5)
 		assertMatch(t, SuffixMatch, true, dir, "fooBarbaz", "Baz", -1, -1, 0)
+		assertMatch(t, SuffixMatch, false, dir, "fooBarbaz", "Foo", -1, -1, 0)
+
+		assertMatch(t, SuffixMatch, false, dir, "fooBarbaz", "baz", 6, 9,
+			scoreMatch*3+bonusConsecutive*2)
+		assertMatch(t, SuffixMatch, false, dir, "fooBarBaZ", "baz", 6, 9,
+			(scoreMatch+bonusCamel123)*3+bonusCamel123*(bonusFirstCharMultiplier-1))
 	}
 }
 
 func TestEmptyPattern(t *testing.T) {
 	for _, dir := range []bool{true, false} {
-		assertMatch(t, FuzzyMatch, true, dir, "foobar", "", 0, 0, 0)
+		assertMatch(t, FuzzyMatchV1, true, dir, "foobar", "", 0, 0, 0)
+		assertMatch(t, FuzzyMatchV2, true, dir, "foobar", "", 0, 0, 0)
 		assertMatch(t, ExactMatchNaive, true, dir, "foobar", "", 0, 0, 0)
 		assertMatch(t, PrefixMatch, true, dir, "foobar", "", 0, 0, 0)
 		assertMatch(t, SuffixMatch, true, dir, "foobar", "", 6, 6, 0)

src/chunklist_test.go

@@ -9,7 +9,7 @@ import (
 
 func TestChunkList(t *testing.T) {
 	// FIXME global
-	sortCriteria = []criterion{byMatchLen, byLength}
+	sortCriteria = []criterion{byScore, byLength}
 
 	cl := NewChunkList(func(s []byte, i int) *Item {
 		return &Item{text: util.ToChars(s), index: int32(i * 2)}

src/constants.go

@@ -8,7 +8,7 @@ import (
 
 const (
 	// Current version
-	version = "0.13.5"
+	version = "0.15.0"
 
 	// Core
 	coordinatorDelayMax  time.Duration = 100 * time.Millisecond
@@ -24,11 +24,17 @@ const (
 	spinnerDuration = 200 * time.Millisecond
 
 	// Matcher
+	numPartitionsMultiplier = 8
+	maxPartitions           = 32
 	progressMinDuration     = 200 * time.Millisecond
 
 	// Capacity of each chunk
 	chunkSize int = 100
 
+	// Pre-allocated memory slices to minimize GC
+	slab16Size int = 100 * 1024 // 200KB * 32 = 12.8MB
+	slab32Size int = 2048       // 8KB * 32 = 256KB
+
 	// Do not cache results of low selectivity queries
 	queryCacheMax int = chunkSize / 5
 

src/core.go

@@ -143,8 +143,8 @@ func Run(opts *Options) {
 	}
 	patternBuilder := func(runes []rune) *Pattern {
 		return BuildPattern(
-			opts.Fuzzy, opts.Extended, opts.Case, forward, opts.Filter == nil,
+			opts.Fuzzy, opts.FuzzyAlgo, opts.Extended, opts.Case, forward,
-			opts.Nth, opts.Delimiter, runes)
+			opts.Filter == nil, opts.Nth, opts.Delimiter, runes)
 	}
 	matcher := NewMatcher(patternBuilder, sort, opts.Tac, eventBox)
 
@@ -158,11 +158,12 @@ func Run(opts *Options) {
 
 		found := false
 		if streamingFilter {
+			slab := util.MakeSlab(slab16Size, slab32Size)
 			reader := Reader{
 				func(runes []byte) bool {
 					item := chunkList.trans(runes, 0)
 					if item != nil {
-						if result, _ := pattern.MatchItem(item); result != nil {
+						if result, _, _ := pattern.MatchItem(item, false, slab); result != nil {
 							fmt.Println(item.text.ToString())
 							found = true
 						}

src/matcher.go

@@ -26,6 +26,7 @@ type Matcher struct {
 	eventBox       *util.EventBox
 	reqBox         *util.EventBox
 	partitions     int
+	slab           []*util.Slab
 	mergerCache    map[string]*Merger
 }
 
@@ -37,13 +38,15 @@ const (
 // NewMatcher returns a new Matcher
 func NewMatcher(patternBuilder func([]rune) *Pattern,
 	sort bool, tac bool, eventBox *util.EventBox) *Matcher {
+	partitions := util.Min(numPartitionsMultiplier*runtime.NumCPU(), maxPartitions)
 	return &Matcher{
 		patternBuilder: patternBuilder,
 		sort:           sort,
 		tac:            tac,
 		eventBox:       eventBox,
 		reqBox:         util.NewEventBox(),
-		partitions:     util.Min(8*runtime.NumCPU(), 32),
+		partitions:     partitions,
+		slab:           make([]*util.Slab, partitions),
 		mergerCache:    make(map[string]*Merger)}
 }
 
@@ -153,12 +156,15 @@ func (m *Matcher) scan(request MatchRequest) (*Merger, bool) {
 
 	for idx, chunks := range slices {
 		waitGroup.Add(1)
-		go func(idx int, chunks []*Chunk) {
+		if m.slab[idx] == nil {
+			m.slab[idx] = util.MakeSlab(slab16Size, slab32Size)
+		}
+		go func(idx int, slab *util.Slab, chunks []*Chunk) {
 			defer func() { waitGroup.Done() }()
 			count := 0
 			allMatches := make([][]*Result, len(chunks))
 			for idx, chunk := range chunks {
-				matches := request.pattern.Match(chunk)
+				matches := request.pattern.Match(chunk, slab)
 				allMatches[idx] = matches
 				count += len(matches)
 				if cancelled.Get() {
@@ -178,7 +184,7 @@ func (m *Matcher) scan(request MatchRequest) (*Merger, bool) {
 				}
 			}
 			resultChan <- partialResult{idx, sliceMatches}
-		}(idx, chunks)
+		}(idx, m.slab[idx], chunks)
 	}
 
 	wait := func() bool {

src/options.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"unicode/utf8"
 
+	"github.com/junegunn/fzf/src/algo"
 	"github.com/junegunn/fzf/src/curses"
 
 	"github.com/junegunn/go-shellwords"
@@ -19,6 +20,7 @@ const usage = `usage: fzf [options]
     -x, --extended        Extended-search mode
                           (enabled by default; +x or --no-extended to disable)
     -e, --exact           Enable Exact-match
+    --algo=TYPE           Fuzzy matching algorithm: [v1|v2] (default: v2)
     -i                    Case-insensitive match (default: smart-case match)
     +i                    Case-sensitive match
     -n, --nth=N[,..]      Comma-separated list of field index expressions
@@ -94,8 +96,7 @@ const (
 type criterion int
 
 const (
-	byMatchLen criterion = iota
+	byScore criterion = iota
-	byBonus
 	byLength
 	byBegin
 	byEnd
@@ -129,6 +130,7 @@ type previewOpts struct {
 // Options stores the values of command-line options
 type Options struct {
 	Fuzzy       bool
+	FuzzyAlgo   algo.Algo
 	Extended    bool
 	Case        Case
 	Nth         []Range
@@ -172,6 +174,7 @@ type Options struct {
 func defaultOptions() *Options {
 	return &Options{
 		Fuzzy:       true,
+		FuzzyAlgo:   algo.FuzzyMatchV2,
 		Extended:    true,
 		Case:        CaseSmart,
 		Nth:         make([]Range, 0),
@@ -179,7 +182,7 @@ func defaultOptions() *Options {
 		Delimiter:   Delimiter{},
 		Sort:        1000,
 		Tac:         false,
-		Criteria:    []criterion{byMatchLen, byBonus, byLength},
+		Criteria:    []criterion{byScore, byLength},
 		Multi:       false,
 		Ansi:        false,
 		Mouse:       true,
@@ -322,6 +325,18 @@ func isAlphabet(char uint8) bool {
 	return char >= 'a' && char <= 'z'
 }
 
+func parseAlgo(str string) algo.Algo {
+	switch str {
+	case "v1":
+		return algo.FuzzyMatchV1
+	case "v2":
+		return algo.FuzzyMatchV2
+	default:
+		errorExit("invalid algorithm (expected: v1 or v2)")
+	}
+	return algo.FuzzyMatchV2
+}
+
 func parseKeyChords(str string, message string) map[int]string {
 	if len(str) == 0 {
 		errorExit(message)
@@ -407,7 +422,7 @@ func parseKeyChords(str string, message string) map[int]string {
 }
 
 func parseTiebreak(str string) []criterion {
-	criteria := []criterion{byMatchLen, byBonus}
+	criteria := []criterion{byScore}
 	hasIndex := false
 	hasLength := false
 	hasBegin := false
@@ -834,6 +849,8 @@ func parseOptions(opts *Options, allArgs []string) {
 		case "-f", "--filter":
 			filter := nextString(allArgs, &i, "query string required")
 			opts.Filter = &filter
+		case "--algo":
+			opts.FuzzyAlgo = parseAlgo(nextString(allArgs, &i, "algorithm required (v1|v2)"))
 		case "--expect":
 			opts.Expect = parseKeyChords(nextString(allArgs, &i, "key names required"), "key names required")
 		case "--tiebreak":
@@ -962,7 +979,9 @@ func parseOptions(opts *Options, allArgs []string) {
 		case "--version":
 			opts.Version = true
 		default:
-			if match, value := optString(arg, "-q", "--query="); match {
+			if match, value := optString(arg, "--algo="); match {
+				opts.FuzzyAlgo = parseAlgo(value)
+			} else if match, value := optString(arg, "-q", "--query="); match {
 				opts.Query = value
 			} else if match, value := optString(arg, "-f", "--filter="); match {
 				opts.Filter = &value

src/pattern.go

@@ -40,6 +40,7 @@ type termSet []term
 // Pattern represents search pattern
 type Pattern struct {
 	fuzzy         bool
+	fuzzyAlgo     algo.Algo
 	extended      bool
 	caseSensitive bool
 	forward       bool
@@ -48,7 +49,7 @@ type Pattern struct {
 	cacheable     bool
 	delimiter     Delimiter
 	nth           []Range
-	procFun       map[termType]func(bool, bool, util.Chars, []rune) algo.Result
+	procFun       map[termType]algo.Algo
 }
 
 var (
@@ -74,7 +75,7 @@ func clearChunkCache() {
 }
 
 // BuildPattern builds Pattern object from the given arguments
-func BuildPattern(fuzzy bool, extended bool, caseMode Case, forward bool,
+func BuildPattern(fuzzy bool, fuzzyAlgo algo.Algo, extended bool, caseMode Case, forward bool,
 	cacheable bool, nth []Range, delimiter Delimiter, runes []rune) *Pattern {
 
 	var asString string
@@ -116,6 +117,7 @@ func BuildPattern(fuzzy bool, extended bool, caseMode Case, forward bool,
 
 	ptr := &Pattern{
 		fuzzy:         fuzzy,
+		fuzzyAlgo:     fuzzyAlgo,
 		extended:      extended,
 		caseSensitive: caseSensitive,
 		forward:       forward,
@@ -124,9 +126,9 @@ func BuildPattern(fuzzy bool, extended bool, caseMode Case, forward bool,
 		cacheable:     cacheable,
 		nth:           nth,
 		delimiter:     delimiter,
-		procFun:       make(map[termType]func(bool, bool, util.Chars, []rune) algo.Result)}
+		procFun:       make(map[termType]algo.Algo)}
 
-	ptr.procFun[termFuzzy] = algo.FuzzyMatch
+	ptr.procFun[termFuzzy] = fuzzyAlgo
 	ptr.procFun[termEqual] = algo.EqualMatch
 	ptr.procFun[termExact] = algo.ExactMatchNaive
 	ptr.procFun[termPrefix] = algo.PrefixMatch
@@ -234,7 +236,7 @@ func (p *Pattern) CacheKey() string {
 }
 
 // Match returns the list of matches Items in the given Chunk
-func (p *Pattern) Match(chunk *Chunk) []*Result {
+func (p *Pattern) Match(chunk *Chunk, slab *util.Slab) []*Result {
 	// ChunkCache: Exact match
 	cacheKey := p.CacheKey()
 	if p.cacheable {
@@ -260,7 +262,7 @@ Loop:
 		}
 	}
 
-	matches := p.matchChunk(chunk, space)
+	matches := p.matchChunk(chunk, space, slab)
 
 	if p.cacheable {
 		_cache.Add(chunk, cacheKey, matches)
@@ -268,18 +270,18 @@ Loop:
 	return matches
 }
 
-func (p *Pattern) matchChunk(chunk *Chunk, space []*Result) []*Result {
+func (p *Pattern) matchChunk(chunk *Chunk, space []*Result, slab *util.Slab) []*Result {
 	matches := []*Result{}
 
 	if space == nil {
 		for _, item := range *chunk {
-			if match, _ := p.MatchItem(item); match != nil {
+			if match, _, _ := p.MatchItem(item, false, slab); match != nil {
 				matches = append(matches, match)
 			}
 		}
 	} else {
 		for _, result := range space {
-			if match, _ := p.MatchItem(result.item); match != nil {
+			if match, _, _ := p.MatchItem(result.item, false, slab); match != nil {
 				matches = append(matches, match)
 			}
 		}
@@ -288,62 +290,75 @@ func (p *Pattern) matchChunk(chunk *Chunk, space []*Result) []*Result {
 }
 
 // MatchItem returns true if the Item is a match
-func (p *Pattern) MatchItem(item *Item) (*Result, []Offset) {
+func (p *Pattern) MatchItem(item *Item, withPos bool, slab *util.Slab) (*Result, []Offset, *[]int) {
 	if p.extended {
-		if offsets, bonus, trimLen := p.extendedMatch(item); len(offsets) == len(p.termSets) {
+		if offsets, bonus, trimLen, pos := p.extendedMatch(item, withPos, slab); len(offsets) == len(p.termSets) {
-			return buildResult(item, offsets, bonus, trimLen), offsets
+			return buildResult(item, offsets, bonus, trimLen), offsets, pos
 		}
-		return nil, nil
+		return nil, nil, nil
 	}
-	offset, bonus, trimLen := p.basicMatch(item)
+	offset, bonus, trimLen, pos := p.basicMatch(item, withPos, slab)
 	if sidx := offset[0]; sidx >= 0 {
 		offsets := []Offset{offset}
-		return buildResult(item, offsets, bonus, trimLen), offsets
+		return buildResult(item, offsets, bonus, trimLen), offsets, pos
 	}
-	return nil, nil
+	return nil, nil, nil
 }
 
-func (p *Pattern) basicMatch(item *Item) (Offset, int, int) {
+func (p *Pattern) basicMatch(item *Item, withPos bool, slab *util.Slab) (Offset, int, int, *[]int) {
 	input := p.prepareInput(item)
 	if p.fuzzy {
-		return p.iter(algo.FuzzyMatch, input, p.caseSensitive, p.forward, p.text)
+		return p.iter(p.fuzzyAlgo, input, p.caseSensitive, p.forward, p.text, withPos, slab)
 	}
-	return p.iter(algo.ExactMatchNaive, input, p.caseSensitive, p.forward, p.text)
+	return p.iter(algo.ExactMatchNaive, input, p.caseSensitive, p.forward, p.text, withPos, slab)
 }
 
-func (p *Pattern) extendedMatch(item *Item) ([]Offset, int, int) {
+func (p *Pattern) extendedMatch(item *Item, withPos bool, slab *util.Slab) ([]Offset, int, int, *[]int) {
 	input := p.prepareInput(item)
 	offsets := []Offset{}
-	var totalBonus int
+	var totalScore int
 	var totalTrimLen int
+	var allPos *[]int
+	if withPos {
+		allPos = &[]int{}
+	}
 	for _, termSet := range p.termSets {
 		var offset Offset
-		var bonus int
+		var currentScore int
 		var trimLen int
 		matched := false
 		for _, term := range termSet {
 			pfun := p.procFun[term.typ]
-			off, pen, tLen := p.iter(pfun, input, term.caseSensitive, p.forward, term.text)
+			off, score, tLen, pos := p.iter(pfun, input, term.caseSensitive, p.forward, term.text, withPos, slab)
 			if sidx := off[0]; sidx >= 0 {
 				if term.inv {
 					continue
 				}
-				offset, bonus, trimLen = off, pen, tLen
+				offset, currentScore, trimLen = off, score, tLen
 				matched = true
+				if withPos {
+					if pos != nil {
+						*allPos = append(*allPos, *pos...)
+					} else {
+						for idx := off[0]; idx < off[1]; idx++ {
+							*allPos = append(*allPos, int(idx))
+						}
+					}
+				}
 				break
 			} else if term.inv {
-				offset, bonus, trimLen = Offset{0, 0}, 0, 0
+				offset, currentScore, trimLen = Offset{0, 0}, 0, 0
 				matched = true
 				continue
 			}
 		}
 		if matched {
 			offsets = append(offsets, offset)
-			totalBonus += bonus
+			totalScore += currentScore
 			totalTrimLen += trimLen
 		}
 	}
-	return offsets, totalBonus, totalTrimLen
+	return offsets, totalScore, totalTrimLen, allPos
 }
 
 func (p *Pattern) prepareInput(item *Item) []Token {
@@ -362,14 +377,18 @@ func (p *Pattern) prepareInput(item *Item) []Token {
 	return ret
 }
 
-func (p *Pattern) iter(pfun func(bool, bool, util.Chars, []rune) algo.Result,
+func (p *Pattern) iter(pfun algo.Algo, tokens []Token, caseSensitive bool, forward bool, pattern []rune, withPos bool, slab *util.Slab) (Offset, int, int, *[]int) {
-	tokens []Token, caseSensitive bool, forward bool, pattern []rune) (Offset, int, int) {
 	for _, part := range tokens {
-		if res := pfun(caseSensitive, forward, *part.text, pattern); res.Start >= 0 {
+		if res, pos := pfun(caseSensitive, forward, *part.text, pattern, withPos, slab); res.Start >= 0 {
 			sidx := int32(res.Start) + part.prefixLength
 			eidx := int32(res.End) + part.prefixLength
-			return Offset{sidx, eidx}, res.Bonus, int(part.trimLength)
+			if pos != nil {
+				for idx := range *pos {
+					(*pos)[idx] += int(part.prefixLength)
 				}
 			}
-	return Offset{-1, -1}, 0, -1
+			return Offset{sidx, eidx}, res.Score, int(part.trimLength), pos
+		}
+	}
+	return Offset{-1, -1}, 0, -1, nil
 }

src/pattern_test.go

@@ -8,6 +8,12 @@ import (
 	"github.com/junegunn/fzf/src/util"
 )
 
+var slab *util.Slab
+
+func init() {
+	slab = util.MakeSlab(slab16Size, slab32Size)
+}
+
 func TestParseTermsExtended(t *testing.T) {
 	terms := parseTerms(true, CaseSmart,
 		"| aaa 'bbb ^ccc ddd$ !eee !'fff !^ggg !hhh$ | ^iii$ ^xxx | 'yyy | | zzz$ | !ZZZ |")
@@ -69,26 +75,32 @@ func TestParseTermsEmpty(t *testing.T) {
 func TestExact(t *testing.T) {
 	defer clearPatternCache()
 	clearPatternCache()
-	pattern := BuildPattern(true, true, CaseSmart, true, true,
+	pattern := BuildPattern(true, algo.FuzzyMatchV2, true, CaseSmart, true, true,
 		[]Range{}, Delimiter{}, []rune("'abc"))
-	res := algo.ExactMatchNaive(
+	res, pos := algo.ExactMatchNaive(
-		pattern.caseSensitive, pattern.forward, util.RunesToChars([]rune("aabbcc abc")), pattern.termSets[0][0].text)
+		pattern.caseSensitive, pattern.forward, util.RunesToChars([]rune("aabbcc abc")), pattern.termSets[0][0].text, true, nil)
 	if res.Start != 7 || res.End != 10 {
 		t.Errorf("%s / %d / %d", pattern.termSets, res.Start, res.End)
 	}
+	if pos != nil {
+		t.Errorf("pos is expected to be nil")
+	}
 }
 
 func TestEqual(t *testing.T) {
 	defer clearPatternCache()
 	clearPatternCache()
-	pattern := BuildPattern(true, true, CaseSmart, true, true, []Range{}, Delimiter{}, []rune("^AbC$"))
+	pattern := BuildPattern(true, algo.FuzzyMatchV2, true, CaseSmart, true, true, []Range{}, Delimiter{}, []rune("^AbC$"))
 
 	match := func(str string, sidxExpected int, eidxExpected int) {
-		res := algo.EqualMatch(
+		res, pos := algo.EqualMatch(
-			pattern.caseSensitive, pattern.forward, util.RunesToChars([]rune(str)), pattern.termSets[0][0].text)
+			pattern.caseSensitive, pattern.forward, util.RunesToChars([]rune(str)), pattern.termSets[0][0].text, true, nil)
 		if res.Start != sidxExpected || res.End != eidxExpected {
 			t.Errorf("%s / %d / %d", pattern.termSets, res.Start, res.End)
 		}
+		if pos != nil {
+			t.Errorf("pos is expected to be nil")
+		}
 	}
 	match("ABC", -1, -1)
 	match("AbC", 0, 3)
@@ -97,17 +109,17 @@ func TestEqual(t *testing.T) {
 func TestCaseSensitivity(t *testing.T) {
 	defer clearPatternCache()
 	clearPatternCache()
-	pat1 := BuildPattern(true, false, CaseSmart, true, true, []Range{}, Delimiter{}, []rune("abc"))
+	pat1 := BuildPattern(true, algo.FuzzyMatchV2, false, CaseSmart, true, true, []Range{}, Delimiter{}, []rune("abc"))
 	clearPatternCache()
-	pat2 := BuildPattern(true, false, CaseSmart, true, true, []Range{}, Delimiter{}, []rune("Abc"))
+	pat2 := BuildPattern(true, algo.FuzzyMatchV2, false, CaseSmart, true, true, []Range{}, Delimiter{}, []rune("Abc"))
 	clearPatternCache()
-	pat3 := BuildPattern(true, false, CaseIgnore, true, true, []Range{}, Delimiter{}, []rune("abc"))
+	pat3 := BuildPattern(true, algo.FuzzyMatchV2, false, CaseIgnore, true, true, []Range{}, Delimiter{}, []rune("abc"))
 	clearPatternCache()
-	pat4 := BuildPattern(true, false, CaseIgnore, true, true, []Range{}, Delimiter{}, []rune("Abc"))
+	pat4 := BuildPattern(true, algo.FuzzyMatchV2, false, CaseIgnore, true, true, []Range{}, Delimiter{}, []rune("Abc"))
 	clearPatternCache()
-	pat5 := BuildPattern(true, false, CaseRespect, true, true, []Range{}, Delimiter{}, []rune("abc"))
+	pat5 := BuildPattern(true, algo.FuzzyMatchV2, false, CaseRespect, true, true, []Range{}, Delimiter{}, []rune("abc"))
 	clearPatternCache()
-	pat6 := BuildPattern(true, false, CaseRespect, true, true, []Range{}, Delimiter{}, []rune("Abc"))
+	pat6 := BuildPattern(true, algo.FuzzyMatchV2, false, CaseRespect, true, true, []Range{}, Delimiter{}, []rune("Abc"))
 
 	if string(pat1.text) != "abc" || pat1.caseSensitive != false ||
 		string(pat2.text) != "Abc" || pat2.caseSensitive != true ||
@@ -120,7 +132,7 @@ func TestCaseSensitivity(t *testing.T) {
 }
 
 func TestOrigTextAndTransformed(t *testing.T) {
-	pattern := BuildPattern(true, true, CaseSmart, true, true, []Range{}, Delimiter{}, []rune("jg"))
+	pattern := BuildPattern(true, algo.FuzzyMatchV2, true, CaseSmart, true, true, []Range{}, Delimiter{}, []rune("jg"))
 	tokens := Tokenize(util.RunesToChars([]rune("junegunn")), Delimiter{})
 	trans := Transform(tokens, []Range{Range{1, 1}})
 
@@ -133,24 +145,29 @@ func TestOrigTextAndTransformed(t *testing.T) {
 				transformed: trans},
 		}
 		pattern.extended = extended
-		matches := pattern.matchChunk(&chunk, nil) // No cache
+		matches := pattern.matchChunk(&chunk, nil, slab) // No cache
-		if matches[0].item.text.ToString() != "junegunn" || string(*matches[0].item.origText) != "junegunn.choi" ||
+		if !(matches[0].item.text.ToString() == "junegunn" &&
-			!reflect.DeepEqual(matches[0].item.transformed, trans) {
+			string(*matches[0].item.origText) == "junegunn.choi" &&
+			reflect.DeepEqual(matches[0].item.transformed, trans)) {
 			t.Error("Invalid match result", matches)
 		}
 
-		match, offsets := pattern.MatchItem(chunk[0])
+		match, offsets, pos := pattern.MatchItem(chunk[0], true, slab)
-		if match.item.text.ToString() != "junegunn" || string(*match.item.origText) != "junegunn.choi" ||
+		if !(match.item.text.ToString() == "junegunn" &&
-			offsets[0][0] != 0 || offsets[0][1] != 5 ||
+			string(*match.item.origText) == "junegunn.choi" &&
-			!reflect.DeepEqual(match.item.transformed, trans) {
+			offsets[0][0] == 0 && offsets[0][1] == 5 &&
-			t.Error("Invalid match result", match)
+			reflect.DeepEqual(match.item.transformed, trans)) {
+			t.Error("Invalid match result", match, offsets, extended)
+		}
+		if !((*pos)[0] == 4 && (*pos)[1] == 0) {
+			t.Error("Invalid pos array", *pos)
 		}
 	}
 }
 
 func TestCacheKey(t *testing.T) {
 	test := func(extended bool, patStr string, expected string, cacheable bool) {
-		pat := BuildPattern(true, extended, CaseSmart, true, true, []Range{}, Delimiter{}, []rune(patStr))
+		pat := BuildPattern(true, algo.FuzzyMatchV2, extended, CaseSmart, true, true, []Range{}, Delimiter{}, []rune(patStr))
 		if pat.CacheKey() != expected {
 			t.Errorf("Expected: %s, actual: %s", expected, pat.CacheKey())
 		}

src/result.go

@@ -19,8 +19,7 @@ type colorOffset struct {
 }
 
 type rank struct {
-	// byMatchLen, byBonus, ...
+	points [4]uint16
-	points [5]uint16
 	index  int32
 }
 
@@ -29,51 +28,36 @@ type Result struct {
 	rank rank
 }
 
-func buildResult(item *Item, offsets []Offset, bonus int, trimLen int) *Result {
+func buildResult(item *Item, offsets []Offset, score int, trimLen int) *Result {
 	if len(offsets) > 1 {
 		sort.Sort(ByOrder(offsets))
 	}
 
 	result := Result{item: item, rank: rank{index: item.index}}
-
-	matchlen := 0
-	prevEnd := 0
-	minBegin := math.MaxInt32
 	numChars := item.text.Length()
+	minBegin := math.MaxUint16
+	maxEnd := 0
+	validOffsetFound := false
 	for _, offset := range offsets {
-		begin := int(offset[0])
+		b, e := int(offset[0]), int(offset[1])
-		end := int(offset[1])
+		if b < e {
-		if prevEnd > begin {
+			minBegin = util.Min(b, minBegin)
-			begin = prevEnd
+			maxEnd = util.Max(e, maxEnd)
-		}
+			validOffsetFound = true
-		if end > prevEnd {
-			prevEnd = end
-		}
-		if end > begin {
-			if begin < minBegin {
-				minBegin = begin
-			}
-			matchlen += end - begin
 		}
 	}
 
 	for idx, criterion := range sortCriteria {
-		var val uint16
+		val := uint16(math.MaxUint16)
 		switch criterion {
-		case byMatchLen:
+		case byScore:
-			if matchlen == 0 {
-				val = math.MaxUint16
-			} else {
-				val = util.AsUint16(matchlen)
-			}
-		case byBonus:
 			// Higher is better
-			val = math.MaxUint16 - util.AsUint16(bonus)
+			val = math.MaxUint16 - util.AsUint16(score)
 		case byLength:
 			// If offsets is empty, trimLen will be 0, but we don't care
 			val = util.AsUint16(trimLen)
 		case byBegin:
-			// We can't just look at item.offsets[0][0] because it can be an inverse term
+			if validOffsetFound {
 				whitePrefixLen := 0
 				for idx := 0; idx < numChars; idx++ {
 					r := item.text.Get(idx)
@@ -83,12 +67,10 @@ func buildResult(item *Item, offsets []Offset, bonus int, trimLen int) *Result {
 					}
 				}
 				val = util.AsUint16(minBegin - whitePrefixLen)
+			}
 		case byEnd:
-			if prevEnd > 0 {
+			if validOffsetFound {
-				val = util.AsUint16(1 + numChars - prevEnd)
+				val = util.AsUint16(1 + numChars - maxEnd)
-			} else {
-				// Empty offsets due to inverse terms.
-				val = 1
 			}
 		}
 		result.rank.points[idx] = val
@@ -106,7 +88,7 @@ func (result *Result) Index() int32 {
 }
 
 func minRank() rank {
-	return rank{index: 0, points: [5]uint16{0, math.MaxUint16, 0, 0, 0}}
+	return rank{index: 0, points: [4]uint16{math.MaxUint16, 0, 0, 0}}
 }
 
 func (result *Result) colorOffsets(matchOffsets []Offset, color int, bold bool, current bool) []colorOffset {
@@ -245,7 +227,7 @@ func (a ByRelevanceTac) Less(i, j int) bool {
 }
 
 func compareRanks(irank rank, jrank rank, tac bool) bool {
-	for idx := 0; idx < 5; idx++ {
+	for idx := 0; idx < 4; idx++ {
 		left := irank.points[idx]
 		right := jrank.points[idx]
 		if left < right {

src/result_test.go

@@ -26,7 +26,7 @@ func TestOffsetSort(t *testing.T) {
 func TestRankComparison(t *testing.T) {
 	rank := func(vals ...uint16) rank {
 		return rank{
-			points: [5]uint16{vals[0], 0, vals[1], vals[2], vals[3]},
+			points: [4]uint16{vals[0], vals[1], vals[2], vals[3]},
 			index:  int32(vals[4])}
 	}
 	if compareRanks(rank(3, 0, 0, 0, 5), rank(2, 0, 0, 0, 7), false) ||
@@ -47,11 +47,15 @@ func TestRankComparison(t *testing.T) {
 // Match length, string length, index
 func TestResultRank(t *testing.T) {
 	// FIXME global
-	sortCriteria = []criterion{byMatchLen, byBonus, byLength}
+	sortCriteria = []criterion{byScore, byLength}
 
 	strs := [][]rune{[]rune("foo"), []rune("foobar"), []rune("bar"), []rune("baz")}
 	item1 := buildResult(&Item{text: util.RunesToChars(strs[0]), index: 1}, []Offset{}, 2, 3)
-	if item1.rank.points[0] != math.MaxUint16 || item1.rank.points[1] != math.MaxUint16-2 || item1.rank.points[2] != 3 || item1.item.index != 1 {
+	if item1.rank.points[0] != math.MaxUint16-2 || // Bonus
+		item1.rank.points[1] != 3 || // Length
+		item1.rank.points[2] != 0 || // Unused
+		item1.rank.points[3] != 0 || // Unused
+		item1.item.index != 1 {
 		t.Error(item1.rank)
 	}
 	// Only differ in index
@@ -71,16 +75,16 @@ func TestResultRank(t *testing.T) {
 	}
 
 	// Sort by relevance
-	item3 := buildResult(&Item{index: 2}, []Offset{Offset{1, 3}, Offset{5, 7}}, 0, 0)
+	item3 := buildResult(&Item{index: 2}, []Offset{Offset{1, 3}, Offset{5, 7}}, 3, 0)
-	item4 := buildResult(&Item{index: 2}, []Offset{Offset{1, 2}, Offset{6, 7}}, 0, 0)
+	item4 := buildResult(&Item{index: 2}, []Offset{Offset{1, 2}, Offset{6, 7}}, 4, 0)
-	item5 := buildResult(&Item{index: 2}, []Offset{Offset{1, 3}, Offset{5, 7}}, 0, 0)
+	item5 := buildResult(&Item{index: 2}, []Offset{Offset{1, 3}, Offset{5, 7}}, 5, 0)
-	item6 := buildResult(&Item{index: 2}, []Offset{Offset{1, 2}, Offset{6, 7}}, 0, 0)
+	item6 := buildResult(&Item{index: 2}, []Offset{Offset{1, 2}, Offset{6, 7}}, 6, 0)
 	items = []*Result{item1, item2, item3, item4, item5, item6}
 	sort.Sort(ByRelevance(items))
-	if items[0] != item6 || items[1] != item4 ||
+	if !(items[0] == item6 && items[1] == item5 &&
-		items[2] != item5 || items[3] != item3 ||
+		items[2] == item4 && items[3] == item3 &&
-		items[4] != item2 || items[5] != item1 {
+		items[4] == item2 && items[5] == item1) {
-		t.Error(items)
+		t.Error(items, item1, item2, item3, item4, item5, item6)
 	}
 }
 

src/terminal.go

@@ -18,6 +18,8 @@ import (
 	"github.com/junegunn/go-runewidth"
 )
 
+// import "github.com/pkg/profile"
+
 type jumpMode int
 
 const (
@@ -73,6 +75,7 @@ type Terminal struct {
 	initFunc   func()
 	suppress   bool
 	startChan  chan bool
+	slab       *util.Slab
 }
 
 type selectedItem struct {
@@ -276,6 +279,7 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 		eventBox:   eventBox,
 		mutex:      sync.Mutex{},
 		suppress:   true,
+		slab:       util.MakeSlab(slab16Size, slab32Size),
 		startChan:  make(chan bool, 1),
 		initFunc: func() {
 			C.Init(opts.Theme, opts.Black, opts.Mouse)
@@ -674,14 +678,25 @@ func (t *Terminal) printHighlighted(result *Result, bold bool, col1 int, col2 in
 	text := make([]rune, item.text.Length())
 	copy(text, item.text.ToRunes())
 	matchOffsets := []Offset{}
+	var pos *[]int
 	if t.merger.pattern != nil {
-		_, matchOffsets = t.merger.pattern.MatchItem(item)
+		_, matchOffsets, pos = t.merger.pattern.MatchItem(item, true, t.slab)
+	}
+	charOffsets := matchOffsets
+	if pos != nil {
+		charOffsets = make([]Offset, len(*pos))
+		for idx, p := range *pos {
+			offset := Offset{int32(p), int32(p + 1)}
+			charOffsets[idx] = offset
+		}
+		sort.Sort(ByOrder(charOffsets))
 	}
 	var maxe int
-	for _, offset := range matchOffsets {
+	for _, offset := range charOffsets {
 		maxe = util.Max(maxe, int(offset[1]))
 	}
-	offsets := result.colorOffsets(matchOffsets, col2, bold, current)
+
+	offsets := result.colorOffsets(charOffsets, col2, bold, current)
 	maxWidth := t.window.Width - 3
 	maxe = util.Constrain(maxe+util.Min(maxWidth/2-2, t.hscrollOff), 0, len(text))
 	if overflow(text, maxWidth) {
@@ -876,6 +891,7 @@ func (t *Terminal) current() string {
 
 // Loop is called to start Terminal I/O
 func (t *Terminal) Loop() {
+	// prof := profile.Start(profile.ProfilePath("/tmp/"))
 	<-t.startChan
 	{ // Late initialization
 		intChan := make(chan os.Signal, 1)
@@ -953,6 +969,7 @@ func (t *Terminal) Loop() {
 		if code <= exitNoMatch && t.history != nil {
 			t.history.append(string(t.input))
 		}
+		// prof.Stop()
 		os.Exit(code)
 	}
 

src/util/slab.go

@@ -0,0 +1,12 @@
+package util
+
+type Slab struct {
+	I16 []int16
+	I32 []int32
+}
+
+func MakeSlab(size16 int, size32 int) *Slab {
+	return &Slab{
+		I16: make([]int16, size16),
+		I32: make([]int32, size32)}
+}

src/util/util.go

@@ -18,6 +18,22 @@ func Max(first int, second int) int {
 	return second
 }
 
+// Max16 returns the largest integer
+func Max16(first int16, second int16) int16 {
+	if first >= second {
+		return first
+	}
+	return second
+}
+
+// Max32 returns the largest 32-bit integer
+func Max32(first int32, second int32) int32 {
+	if first > second {
+		return first
+	}
+	return second
+}
+
 // Min returns the smallest integer
 func Min(first int, second int) int {
 	if first <= second {
@@ -34,14 +50,6 @@ func Min32(first int32, second int32) int32 {
 	return second
 }
 
-// Max32 returns the largest 32-bit integer
-func Max32(first int32, second int32) int32 {
-	if first > second {
-		return first
-	}
-	return second
-}
-
 // Constrain32 limits the given 32-bit integer with the upper and lower bounds
 func Constrain32(val int32, min int32, max int32) int32 {
 	if val < min {

test/test_go.rb

@@ -517,162 +517,91 @@ class TestGoFZF < TestBase
     assert_equal input, `#{FZF} -f"!z" -x --tiebreak end < #{tempname}`.split($/)
   end
 
-  # Since 0.11.2
+  def test_tiebreak_index_begin
-  def test_tiebreak_list
+    writelines tempname, [
-    input = %w[
+      'xoxxxxxoxx',
-      f-o-o-b-a-r
+      'xoxxxxxox',
-      foobar----
+      'xxoxxxoxx',
-      --foobar
+      'xxxoxoxxx',
-      ----foobar
+      'xxxxoxox',
-      foobar--
+      '  xxoxoxxx',
-      --foobar--
-      foobar
     ]
-    writelines tempname, input
 
-    assert_equal %w[
+    assert_equal [
-      foobar----
+      'xxxxoxox',
-      --foobar
+      '  xxoxoxxx',
-      ----foobar
+      'xxxoxoxxx',
-      foobar--
+      'xxoxxxoxx',
-      --foobar--
+      'xoxxxxxox',
-      foobar
+      'xoxxxxxoxx',
-      f-o-o-b-a-r
+    ], `#{FZF} -foo < #{tempname}`.split($/)
-    ], `#{FZF} -ffb --tiebreak=index < #{tempname}`.split($/)
 
-    by_length = %w[
+    assert_equal [
-      foobar
+      'xxxoxoxxx',
-      --foobar
+      'xxxxoxox',
-      foobar--
+      '  xxoxoxxx',
-      foobar----
+      'xxoxxxoxx',
-      ----foobar
+      'xoxxxxxoxx',
-      --foobar--
+      'xoxxxxxox',
-      f-o-o-b-a-r
+    ], `#{FZF} -foo --tiebreak=index < #{tempname}`.split($/)
-    ]
-    assert_equal by_length, `#{FZF} -ffb < #{tempname}`.split($/)
-    assert_equal by_length, `#{FZF} -ffb --tiebreak=length < #{tempname}`.split($/)
 
-    assert_equal %w[
+    # Note that --tiebreak=begin is now based on the first occurrence of the
-      foobar
+    # first character on the pattern
-      foobar--
+    assert_equal [
-      --foobar
+      '  xxoxoxxx',
-      foobar----
+      'xxxoxoxxx',
-      --foobar--
+      'xxxxoxox',
-      ----foobar
+      'xxoxxxoxx',
-      f-o-o-b-a-r
+      'xoxxxxxoxx',
-    ], `#{FZF} -ffb --tiebreak=length,begin < #{tempname}`.split($/)
+      'xoxxxxxox',
+    ], `#{FZF} -foo --tiebreak=begin < #{tempname}`.split($/)
 
-    assert_equal %w[
+    assert_equal [
-      foobar
+      '  xxoxoxxx',
-      --foobar
+      'xxxoxoxxx',
-      foobar--
+      'xxxxoxox',
-      ----foobar
+      'xxoxxxoxx',
-      --foobar--
+      'xoxxxxxox',
-      foobar----
+      'xoxxxxxoxx',
-      f-o-o-b-a-r
+    ], `#{FZF} -foo --tiebreak=begin,length < #{tempname}`.split($/)
-    ], `#{FZF} -ffb --tiebreak=length,end < #{tempname}`.split($/)
-
-    assert_equal %w[
-      foobar----
-      foobar--
-      foobar
-      --foobar
-      --foobar--
-      ----foobar
-      f-o-o-b-a-r
-    ], `#{FZF} -ffb --tiebreak=begin < #{tempname}`.split($/)
-
-    by_begin_end = %w[
-      foobar
-      foobar--
-      foobar----
-      --foobar
-      --foobar--
-      ----foobar
-      f-o-o-b-a-r
-    ]
-    assert_equal by_begin_end, `#{FZF} -ffb --tiebreak=begin,length < #{tempname}`.split($/)
-    assert_equal by_begin_end, `#{FZF} -ffb --tiebreak=begin,end < #{tempname}`.split($/)
-
-    assert_equal %w[
-      --foobar
-      ----foobar
-      foobar
-      foobar--
-      --foobar--
-      foobar----
-      f-o-o-b-a-r
-    ], `#{FZF} -ffb --tiebreak=end < #{tempname}`.split($/)
-
-    by_begin_end = %w[
-      foobar
-      --foobar
-      ----foobar
-      foobar--
-      --foobar--
-      foobar----
-      f-o-o-b-a-r
-    ]
-    assert_equal by_begin_end, `#{FZF} -ffb --tiebreak=end,begin < #{tempname}`.split($/)
-    assert_equal by_begin_end, `#{FZF} -ffb --tiebreak=end,length < #{tempname}`.split($/)
   end
 
-  def test_tiebreak_white_prefix
+  def test_tiebreak_end
     writelines tempname, [
-      'f o o b a r',
+      'xoxxxxxxxx',
-      '    foo bar',
+      'xxoxxxxxxx',
-      '    foobar',
+      'xxxoxxxxxx',
-      '----foo bar',
+      'xxxxoxxxx',
-      '----foobar',
+      'xxxxxoxxx',
-      '  foo bar',
+      '  xxxxoxxx',
-      '  foobar--',
-      '  foobar',
-      '--foo bar',
-      '--foobar',
-      'foobar',
     ]
 
     assert_equal [
-      '    foobar',
+      '  xxxxoxxx',
-      '  foobar',
+      'xxxxoxxxx',
-      'foobar',
+      'xxxxxoxxx',
-      '  foobar--',
+      'xoxxxxxxxx',
-      '--foobar',
+      'xxoxxxxxxx',
-      '----foobar',
+      'xxxoxxxxxx',
-      '    foo bar',
+    ], `#{FZF} -fo < #{tempname}`.split($/)
-      '  foo bar',
-      '--foo bar',
-      '----foo bar',
-      'f o o b a r',
-    ], `#{FZF} -ffb < #{tempname}`.split($/)
 
     assert_equal [
-      '    foobar',
+      'xxxxxoxxx',
-      '  foobar--',
+      '  xxxxoxxx',
-      '  foobar',
+      'xxxxoxxxx',
-      'foobar',
+      'xxxoxxxxxx',
-      '--foobar',
+      'xxoxxxxxxx',
-      '----foobar',
+      'xoxxxxxxxx',
-      '    foo bar',
+    ], `#{FZF} -fo --tiebreak=end < #{tempname}`.split($/)
-      '  foo bar',
-      '--foo bar',
-      '----foo bar',
-      'f o o b a r',
-    ], `#{FZF} -ffb --tiebreak=begin < #{tempname}`.split($/)
 
     assert_equal [
-      '    foobar',
+      '  xxxxoxxx',
-      '  foobar',
+      'xxxxxoxxx',
-      'foobar',
+      'xxxxoxxxx',
-      '  foobar--',
+      'xxxoxxxxxx',
-      '--foobar',
+      'xxoxxxxxxx',
-      '----foobar',
+      'xoxxxxxxxx',
-      '    foo bar',
+    ], `#{FZF} -fo --tiebreak=end,length,begin < #{tempname}`.split($/)
-      '  foo bar',
-      '--foo bar',
-      '----foo bar',
-      'f o o b a r',
-    ], `#{FZF} -ffb --tiebreak=begin,length < #{tempname}`.split($/)
   end
 
   def test_tiebreak_length_with_nth
@@ -748,17 +677,6 @@ class TestGoFZF < TestBase
     assert_equal output, `#{FZF} -fi -n2,1..2 < #{tempname}`.split($/)
   end
 
-  def test_tiebreak_end_backward_scan
-    input = %w[
-      foobar-fb
-      fubar
-    ]
-    writelines tempname, input
-
-    assert_equal input.reverse, `#{FZF} -f fb < #{tempname}`.split($/)
-    assert_equal input, `#{FZF} -f fb --tiebreak=end < #{tempname}`.split($/)
-  end
-
   def test_invalid_cache
     tmux.send_keys "(echo d; echo D; echo x) | #{fzf '-q d'}", :Enter
     tmux.until { |lines| lines[-2].include? '2/3' }