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require 'zipf'
require_relative 'grammar'
require_relative 'hypergraph'
module Parse
def Parse::visit i, l, r, x=0
i.upto(r-x) { |span|
l.upto(r-span) { |k|
yield k, k+span
}
}
end
class Chart
def initialize n
@n = n
@m = []
(n+1).times {
a = []
(n+1).times { a << [] }
@m << a
}
@b = {}
end
def at i, j
@m[i][j]
end
def add item, i, j
at(i,j) << item
@b["#{i},#{j},#{item.lhs.symbol}"] = true
end
def has symbol, i, j
return @b["#{i},#{j},#{symbol}"]
end
def to_hg weights=SparseVector.new
nodes = []
edges = []
nodes_by_id = {}
nodes << HG::Node.new(-1, "root", [-1,-1])
nodes_by_id[-1] = nodes.last
id = 0
seen = {}
Parse::visit(1, 0, @n) { |i,j|
self.at(i,j).each { |item|
_ = "#{item.lhs.symbol},#{i},#{j}"
if !seen[_]
nodes << HG::Node.new(id, item.lhs.symbol, [i,j])
nodes_by_id[id] = nodes.last
seen[_] = id
id += 1
end
}
}
Parse::visit(1, 0, @n) { |i,j|
self.at(i,j).each { |item|
edges << HG::Hyperedge.new(nodes_by_id[seen[item.lhs.symbol+','+i.to_s+','+j.to_s]], \
(item.tail_spans.empty? ? [nodes_by_id[-1]] : item.rhs.zip((0..item.rhs.size-1).map{|q| item.tail_spans[q] }).select{|x| x[0].class==Grammar::NT }.map{|x| nodes_by_id[seen["#{x[0].symbol},#{x[1].left},#{x[1].right}"]]}), \
Math.exp(weights.dot(item.f)),
item.f,
Grammar::Rule.new(item.lhs, item.rhs, item.target, item.map, item.f), \
)
edges.last.head.incoming << edges.last
edges.last.tails.each { |n| n.outgoing << edges.last }
}
}
return HG::Hypergraph.new(nodes, edges, nodes_by_id)
end
end
Span = Struct.new(:left, :right)
class Item < Grammar::Rule
attr_accessor :left, :right, :tail_spans, :dot, :f
def initialize rule_or_item, left, right, dot
@lhs = Grammar::NT.new rule_or_item.lhs.symbol, rule_or_item.lhs.index
@left = left
@right = right
@rhs = []
@tail_spans = {} # refers to source side, use @map
@f = rule_or_item.f
@map = (rule_or_item.map ? rule_or_item.map.dup : [])
rule_or_item.rhs.each_with_index { |x,i| # duplicate rhs partially
@rhs << x
if x.class == Grammar::NT
begin
if i >= dot
@tail_spans[i] = Span.new(-1, -1)
else
@tail_spans[i] = rule_or_item.tail_spans[i].dup
end
rescue
@tail_spans[i] = Span.new(-1, -1)
end
end
}
@dot = dot
@target = rule_or_item.target
end
def to_s
"(#{@left}, #{@right}) [#{tail_spans.map{|k,v| k.to_s+'('+v.left.to_s+','+v.right.to_s+')'}.join ' '}] {#{@map.to_s.delete('[]')}} #{lhs} -> #{rhs.map{|i|i.to_s}.insert(@dot,'*').join ' '} [dot@#{@dot}] ||| #{@target.map{|x|x.to_s}.join ' '}"
end
end
def Parse::init input, n, active_chart, passive_chart, grammar
grammar.flat.each { |r|
input.each_index { |i|
if input[i, r.rhs.size] == r.rhs.map { |x| x.word }
passive_chart.add Item.new(r, i, i+r.rhs.size, r.rhs.size), i, i+r.rhs.size
end
}
}
end
def Parse::scan item, input, limit, passive_chart
while item.rhs[item.dot].class == Grammar::T
return false if item.right==limit
if item.rhs[item.dot].word == input[item.right]
item.dot += 1
item.right += 1
else
return false
end
end
return true
end
def Parse::parse input, n, active_chart, passive_chart, grammar
visit(1, 0, n) { |i,j|
STDERR.write " span(#{i},#{j})\n"
# try to apply rules starting with T
grammar.start_t.select { |r| r.rhs.first.word == input[i] }.each { |r|
new_item = Item.new r, i, i, 0
active_chart.at(i,j) << new_item if scan new_item, input, j, passive_chart
}
# seed active chart
grammar.start_nt.each { |r|
next if r.rhs.size > j-i
active_chart.at(i,j) << Item.new(r, i, i, 0)
}
# parse
new_symbols = []
remaining_items = []
while !active_chart.at(i,j).empty?
active_item = active_chart.at(i,j).pop
advanced = false
visit(1, i, j, 1) { |k,l|
if passive_chart.has active_item.rhs[active_item.dot].symbol, k, l
if k == active_item.right
new_item = Item.new active_item, active_item.left, l, active_item.dot+1
new_item.tail_spans[new_item.dot-1] = Span.new(k,l)
if scan new_item, input, j, passive_chart
if new_item.dot == new_item.rhs.size
if new_item.left == i && new_item.right == j
new_symbols << new_item.lhs.symbol if !new_symbols.include? new_item.lhs.symbol
passive_chart.add new_item, i, j
advanced = true
end
else
if new_item.right+(new_item.rhs.size-(new_item.dot)) <= j
active_chart.at(i,j) << new_item
advanced = true
end
end
end
end
end
}
if !advanced
remaining_items << active_item
end
end
# 'self-filling' step
new_symbols.each { |s|
remaining_items.each { |item|
next if item.dot!=0
next if item.rhs[item.dot].class!=Grammar::NT
if item.rhs[item.dot].symbol == s
new_item = Item.new item, i, j, item.dot+1
new_item.tail_spans[new_item.dot-1] = Span.new(i,j)
if new_item.dot==new_item.rhs.size
new_symbols << new_item.lhs.symbol if !new_symbols.include? new_item.lhs.symbol
passive_chart.add new_item, i, j
end
end
}
}
}
end
end #module
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