215 lines
6.1 KiB
Julia
215 lines
6.1 KiB
Julia
##############################################################################
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##
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## Find common prefixes (up to lim. -1 means Inf)
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## Assumes length(s1) <= length(s2)
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##############################################################################
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function common_prefix(s1::AbstractString, s2::AbstractString, lim::Integer = -1)
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start1 = start(s1)
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start2 = start(s2)
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l = 0
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while !done(s1, start1) && (l < lim || lim < 0)
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ch1, nextstart1 = next(s1, start1)
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ch2, nextstart2 = next(s2, start2)
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ch1 != ch2 && break
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l += 1
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start1, start2 = nextstart1, nextstart2
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end
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return l, start1, start2
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end
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##############################################################################
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##
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## Hamming
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##
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##############################################################################
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function evaluate(dist::Hamming, s1::AbstractString, s2::AbstractString, len1::Integer, len2::Integer)
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count = 0
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for (ch1, ch2) in zip(s1, s2)
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count += ch1 != ch2
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end
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count += len2 - len1
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return count
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end
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hamming(s1::AbstractString, s2::AbstractString) = evaluate(Hamming(), s1, s2)
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##############################################################################
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##
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## Levenshtein
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## Source: http://blog.softwx.net/2014/12/optimizing-levenshtein-algorithm-in-c.html
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##
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##############################################################################
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type Levenshtein <: SemiMetric end
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function evaluate(dist::Levenshtein, s1::AbstractString, s2::AbstractString, len1::Integer, len2::Integer)
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len2 == 0 && return 0
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# prefix common to both strings can be ignored
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k, start1, start2 = common_prefix(s1, s2)
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done(s1, start1) && return len2 - k
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# distance initialized to first row of matrix
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# => distance between "" and s2[1:i}
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v0 = Array(Int, len2 - k)
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@inbounds for i2 in 1:(len2 - k)
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v0[i2] = i2
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end
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current = zero(0)
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state1 = start1
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i1 = 0
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while !done(s1, state1)
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i1 += 1
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ch1, state1 = next(s1, state1)
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left = (i1 - 1)
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current = (i1 - 1)
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state2 = start2
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i2 = 0
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while !done(s2, state2)
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i2 += 1
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ch2, state2 = next(s2, state2)
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# update
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above, current, left = current, left, v0[i2]
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if ch1 != ch2
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# substitution
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current = min(current + 1,
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above + 1,
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left + 1)
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end
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v0[i2] = current
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end
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end
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return current
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end
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function levenshtein(s1::AbstractString, s2::AbstractString)
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evaluate(Levenshtein(), s1, s2)
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end
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##############################################################################
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##
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## Damerau Levenshtein
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## Source: http://blog.softwx.net/2015/01/optimizing-damerau-levenshtein_15.html
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##
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##############################################################################
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type DamerauLevenshtein <: SemiMetric end
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function evaluate(dist::DamerauLevenshtein, s1::AbstractString, s2::AbstractString, len1::Integer, len2::Integer)
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len2 == 0 && return 0
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# prefix common to both strings can be ignored
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k, start1, start2 = common_prefix(s1, s2)
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done(s1, start1) && return len2 - k
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v0 = Array(Int, len2 - k)
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@inbounds for i2 in 1:(len2 - k)
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v0[i2] = i2
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end
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v2 = Array(Int, len2 - k)
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ch1, = next(s1, start1)
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current = 0
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state1 = start1
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i1 = 0
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while !done(s1, state1)
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i1 += 1
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prevch1 = ch1
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ch1, state1 = next(s1, state1)
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ch2, = next(s2, start2)
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left = (i1 - 1)
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current = i1
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nextTransCost = 0
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state2 = start2
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i2 = 0
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while !done(s2, state2)
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i2 += 1
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prevch2 = ch2
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ch2, state2 = next(s2, state2)
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above = current
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thisTransCost = nextTransCost
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nextTransCost = v2[i2]
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# cost of diagonal (substitution)
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v2[i2] = current = left
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# left now equals current cost (which will be diagonal at next iteration)
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left = v0[i2]
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if ch1 != ch2
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# insertion
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if left < current
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current = left
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end
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# deletion
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if above < current
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current = above
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end
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current += 1
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if i1 != 1 && i2 != 1 && ch1 == prevch2 && prevch1 == ch2
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thisTransCost += 1
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if thisTransCost < current
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current = thisTransCost
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end
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end
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end
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v0[i2] = current
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end
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end
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return current
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end
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damerau_levenshtein(s1::AbstractString, s2::AbstractString) = evaluate(DamerauLevenshtein(), s1, s2)
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##############################################################################
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##
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## JaroWinkler
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##
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##############################################################################
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type Jaro <: SemiMetric end
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function evaluate(dist::Jaro, s1::AbstractString, s2::AbstractString, len1::Integer, len2::Integer)
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len2 == 0 && return 0.0
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maxdist = max(0, div(len2, 2) - 1)
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m = 0 # matching characters
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t = 0 # half number of transpositions
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flag = fill(false, len2)
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prevpos = 0
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i1 = 0
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startstate2 = start(s2)
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starti2 = 0
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for ch1 in s1
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i1 += 1
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if starti2 < i1 - maxdist - 1
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startstate2 = nextind(s2, startstate2)
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starti2 += 1
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end
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i2 = starti2
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state2 = startstate2
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while !done(s2, state2) && i2 < i1 + maxdist
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ch2, state2 = next(s2, state2)
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i2 += 1
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if ch1 == ch2 && !flag[i2]
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m += 1
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# if match is before the index of previous match
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if i2 < prevpos
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t += 1
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end
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prevpos = max(i2, prevpos)
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flag[i2] = true
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break
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end
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end
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end
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m == 0.0 && return 1.0
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score = (m / len1 + m / len2 + (m - t) / m) / 3.0
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return 1.0 - score
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end
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jaro(s1::AbstractString, s2::AbstractString) = evaluate(Jaro(), s1, s2)
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