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

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

/* file : partitioned-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
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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*/

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

describe('PartitionedBloomFilter', () => {
  const targetRate = 0.001

  describe('construction', () => {
    it('should add element to the filter', () => {
      const filter = PartitionedBloomFilter.create(15, targetRate)
      filter.add('alice')
      filter.add('bob')
    })

    it('should build a new filter using #from', () => {
      const data = ['alice', 'bob', 'carl']
      const filter = PartitionedBloomFilter.from(data, targetRate)
      filter.has('alice').should.equal(true)
      filter.has('bob').should.equal(true)
      filter.has('carl').should.equal(true)
      filter.rate().should.be.closeTo(targetRate, 0.1)
    })
  })

  describe('#has', () => {
    const getFilter = () => {
      const filter = PartitionedBloomFilter.create(15, targetRate)
      filter.add('alice')
      filter.add('bob')
      filter.add('carl')
      return filter
    }

    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('#equals', () => {
    it('should returns True when two filters are equals', () => {
      const first = PartitionedBloomFilter.from(
        ['alice', 'bob', 'carol'],
        targetRate,
        0.5
      )
      const other = PartitionedBloomFilter.from(
        ['alice', 'bob', 'carol'],
        targetRate,
        0.5
      )
      first.equals(other).should.equal(true)
    })

    it('should returns False when two filters have different sizes', () => {
      const first = new PartitionedBloomFilter(15, 4, 0.5)
      const other = new PartitionedBloomFilter(10, 4, 0.5)
      first.equals(other).should.equal(false)
    })

    it('should returns False when two filters have different nb. of hash functions', () => {
      const first = new PartitionedBloomFilter(15, 4, 0.5)
      const other = new PartitionedBloomFilter(15, 2, 0.5)
      first.equals(other).should.equal(false)
    })

    it('should returns False when two filters have different load factor', () => {
      const first = new PartitionedBloomFilter(15, 4, 0.5)
      const other = new PartitionedBloomFilter(15, 2, 0.4)
      first.equals(other).should.equal(false)
    })

    it('should returns False when two filters have different content', () => {
      const first = PartitionedBloomFilter.from(
        ['alice', 'bob', 'carol'],
        targetRate,
        0.5
      )
      const other = PartitionedBloomFilter.from(
        ['alice', 'bob', 'daniel'],
        targetRate,
        0.5
      )
      first.equals(other).should.equal(false)
    })
  })

  describe('#saveAsJSON', () => {
    const getFilter = () => {
      const filter = PartitionedBloomFilter.create(15, targetRate)
      filter.add('alice')
      filter.add('bob')
      filter.add('carl')
      return filter
    }

    it('should export a partitioned bloom filter to a JSON object', () => {
      const filter = getFilter()
      const exported = filter.saveAsJSON()
      exported.type.should.equal('PartitionedBloomFilter')
      exported._capacity.should.equal(15)
      exported._size.should.equal(filter._size)
      exported._loadFactor.should.equal(filter._loadFactor)
      exported._nbHashes.should.equal(filter._nbHashes)
      exported._filter.should.deep.equal(filter._filter.map(f => f.export()))
    })

    it('should create a partitioned bloom filter from a JSON export', () => {
      const filter = getFilter()
      const exported = filter.saveAsJSON()
      const newFilter = PartitionedBloomFilter.fromJSON(exported)
      newFilter.seed.should.equal(filter.seed)
      newFilter._capacity.should.equal(filter._capacity)
      newFilter._size.should.equal(filter._size)
      newFilter._loadFactor.should.equal(filter._loadFactor)
      newFilter._m.should.equal(filter._m)
      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: 'PartitionedBloomFilter'},
        {type: 'PartitionedBloomFilter', _capacity: 1},
        {type: 'PartitionedBloomFilter', _capacity: 1, _errorRate: 1},
      ]

      invalids.forEach(json => {
        ;(() => PartitionedBloomFilter.fromJSON(json)).should.throw(Error)
      })
    })
  })
  describe('Performance test', () => {
    const max = 1000
    it(`should not return an error when inserting and querying for ${max} elements`, () => {
      const filter = PartitionedBloomFilter.create(max, targetRate, 0.5)
      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)
        if (has) falsePositive++
      }
      const currentrate = falsePositive / tries
      currentrate.should.be.closeTo(targetRate, targetRate)
    })
  })
})