bloom-filters/test/counting-bloom-filter-test.js

JS implementation of probabilistic data structures: Bloom Filter (and its derived), HyperLogLog, Count-Min Sketch, Top-K and MinHash

/* file : counting-bloom-filter-test.js
MIT License

Copyright (c) 2017 Thomas Minier & Arnaud Grall

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

require('chai').should()
const {CountingBloomFilter} = require('../dist/api.js')

describe('CountingBloomFilter', () => {
  const targetRate = 0.1

  describe('construction', () => {
    it('should add element to the filter with #add', () => {
      const filter = CountingBloomFilter.create(15, targetRate)
      filter.add('alice')
      filter.add('bob')
      filter.length.should.equal(2)
    })

    it('should build a new filter using #from', () => {
      const data = ['alice', 'bob', 'carl']
      const expectedSize = Math.ceil(
        -((data.length * Math.log(targetRate)) / Math.pow(Math.log(2), 2))
      )
      const expectedHashes = Math.ceil(
        (expectedSize / data.length) * Math.log(2)
      )
      const filter = CountingBloomFilter.from(data, targetRate)
      filter.size.should.equal(expectedSize)
      filter._nbHashes.should.equal(expectedHashes)
      filter.length.should.equal(data.length)
      filter.rate().should.be.closeTo(targetRate, 0.1)
    })
  })

  describe('#has', () => {
    const getFilter = () =>
      CountingBloomFilter.from(['alice', 'bob', 'carl'], targetRate)
    it('should return false for elements that are definitively not in the set', () => {
      const filter = getFilter()
      filter.has('daniel').should.equal(false)
      filter.has('al').should.equal(false)
    })

    it('should return true for elements that might be in the set', () => {
      const filter = getFilter()
      filter.has('alice').should.equal(true)
      filter.has('bob').should.equal(true)
      filter.has('carl').should.equal(true)
    })
  })

  describe('#remove', () => {
    it('should allow deletion of items', () => {
      const filter = CountingBloomFilter.from(
        ['alice', 'bob', 'carl'],
        targetRate
      )
      filter.remove('bob')
      filter.has('alice').should.equal(true)
      filter.has('bob').should.equal(false)
      filter.has('carl').should.equal(true)
    })
  })

  describe('#equals', () => {
    it('should returns True when two filters are equals', () => {
      const first = CountingBloomFilter.from(
        ['alice', 'bob', 'carol'],
        targetRate
      )
      const other = CountingBloomFilter.from(
        ['alice', 'bob', 'carol'],
        targetRate
      )
      first.equals(other).should.equal(true)
    })

    it('should returns False when two filters have different sizes', () => {
      const first = new CountingBloomFilter(15, 4)
      const other = new CountingBloomFilter(10, 4)
      first.equals(other).should.equal(false)
    })

    it('should returns False when two filters have different nb. of hash functions', () => {
      const first = new CountingBloomFilter(15, 4)
      const other = new CountingBloomFilter(15, 2)
      first.equals(other).should.equal(false)
    })

    it('should returns False when two filters have different content', () => {
      const first = CountingBloomFilter.from(
        ['alice', 'bob', 'carol'],
        targetRate
      )
      const other = CountingBloomFilter.from(
        ['alice', 'bob', 'daniel'],
        targetRate
      )
      first.equals(other).should.equal(false)
    })
  })

  describe('#saveAsJSON', () => {
    const getFilter = () =>
      CountingBloomFilter.from(['alice', 'bob', 'carl'], targetRate)
    it('should export a bloom filter to a JSON object', () => {
      const filter = getFilter()
      const exported = filter.saveAsJSON()
      exported._seed.should.equal(filter.seed)
      exported.type.should.equal('CountingBloomFilter')
      exported._size.should.equal(filter.size)
      exported._length.should.equal(filter.length)
      exported._nbHashes.should.equal(filter._nbHashes)
      exported._filter.should.deep.equal(filter._filter)
    })

    it('should create a bloom filter from a JSON export', () => {
      const filter = getFilter()
      const exported = filter.saveAsJSON()
      const newFilter = CountingBloomFilter.fromJSON(exported)
      newFilter.seed.should.equal(filter.seed)
      newFilter.size.should.equal(filter._size)
      newFilter.length.should.equal(filter._length)
      newFilter._nbHashes.should.equal(filter._nbHashes)
      newFilter._filter.should.deep.equal(filter._filter)
    })

    it('should reject imports from invalid JSON objects', () => {
      const invalids = [
        {type: 'something'},
        {type: 'CountingBloomFilter'},
        {type: 'CountingBloomFilter', _size: 1},
        {type: 'CountingBloomFilter', _size: 1, _length: 1},
        {type: 'CountingBloomFilter', size: 1, length: 1, _nbHashes: 2},
        {
          type: 'CountingBloomFilter',
          _size: 1,
          _length: 1,
          _nbHashes: 2,
          _seed: 1,
        },
      ]

      invalids.forEach(json => {
        ;(() => CountingBloomFilter.fromJSON(json)).should.throw(Error)
      })
    })
  })

  describe('Performance test', () => {
    const max = 1000
    const targetedRate = 0.01
    it('should not return an error when inserting ' + max + ' elements', () => {
      const filter = CountingBloomFilter.create(max, targetedRate)
      for (let i = 0; i < max; ++i) filter.add('' + i)
      for (let i = 0; i < max; ++i) {
        filter.has('' + i).should.equal(true)
      }
      let current
      let falsePositive = 0
      let tries = 0
      for (let i = max; i < max * 11; ++i) {
        tries++
        current = i
        const has = filter.has('' + current, true)
        if (has) falsePositive++
      }
      const currentrate = falsePositive / tries
      currentrate.should.be.closeTo(targetedRate, targetedRate)
    })
  })
})