Class: Decompound::Packer

Inherits:
Object
  • Object
show all
Defined in:
lib/decompound/packer.rb

Overview

Compiles the trained JSON probability tables into the binary runtime model, see Decompound::Model

Constant Summary collapse

POSITIONS = 
{"prefix" => Model::PREFIX, "infix" => Model::INFIX, "suffix" => Model::SUFFIX}.freeze

Instance Method Summary collapse

Instance Method Details

#pack(probabilities) ⇒ Object 



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# File 'lib/decompound/packer.rb', line 11

def pack(probabilities)
  entries = Hash.new { |hash, key| hash[key] = [Model::MISSING] * 3 }
  POSITIONS.each do |position, slot|
    probabilities.fetch(position).each do |ngram, probability|
      entries[ngram.b][slot] = (probability.clamp(0.0, 1.0) * Model::SCALE).round
    end
  end

  keys = entries.keys.sort!
  offsets = []
  blob = +""
  buckets = +""
  bucket_count = 0
  previous_prefix = nil
  keys.each_with_index do |key, index|
    prefix = key.byteslice(0, 3).ljust(3, "\0")
    if prefix != previous_prefix
      buckets << prefix << [index].pack("V")
      bucket_count += 1
      previous_prefix = prefix
    end
    offsets << blob.bytesize
    blob << key
  end
  offsets << blob.bytesize

  Model::MAGIC.b +
    [keys.length, bucket_count].pack("VV") +
    buckets +
    offsets.pack("V*") +
    keys.flat_map { |key| entries.fetch(key) }.pack("C*") +
    blob
end