human/demo/facematch/node-match.md

NodeJS Multi-Threading Match Solution

See node-match.js and node-match-worker.js

Methods and Properties in node-match

• createBuffer: create shared buffer array
  single copy of data regardless of number of workers
  fixed size based on options.dbMax
• appendRecord: add additional batch of descriptors to buffer
  can append batch of records to buffer at anytime
  workers are informed of the new content after append has been completed
• workersStart: start or expand pool of threadPoolSize workers
  each worker runs node-match-worker and listens for messages from main thread
  can shutdown workers or create additional worker threads on-the-fly
  safe against workers that exit
• workersClose: close workers in a pool
  first request workers to exit then terminate after timeout
• match: dispach a match job to a worker
  returns first match that satisfies minThreshold
  assigment to workers using round-robin
  since timing for each job is near-fixed and predictable
• getDescriptor: get descriptor array for a given id from a buffer
• fuzDescriptor: small randomize descriptor content for harder match
• getLabel: fetch label for resolved descriptor index
• loadDB: load face database from a JSON file dbFile
  extracts descriptors and adds them to buffer
  extracts labels and maintains them in main thread
  for test purposes loads same database dbFact times to create a very large database

node-match runs in a listens for messages from workers until maxJobs have been reached

Performance

Linear performance decrease that depends on number of records in database
Non-linear performance that increases with number of worker threads due to communication overhead

• Face dataase with 10k records:

  threadPoolSize: 1 => ~60 ms / match job
  threadPoolSize: 6 => ~25 ms / match job

• Face database with 50k records:

  threadPoolSize: 1 => ~300 ms / match job
  threadPoolSize: 6 => ~100 ms / match job

• Face database with 100k records:

  threadPoolSize: 1 => ~600 ms / match job
  threadPoolSize: 6 => ~200 ms / match job

Example

node node-match

2021-10-13 07:53:36 INFO:  options: { dbFile: './faces.json', dbMax: 10000, threadPoolSize: 6, workerSrc: './node-match-worker.js', debug: false, minThreshold: 0.9, descLength: 1024 }
2021-10-13 07:53:36 DATA:  created shared buffer: { maxDescriptors: 10000, totalBytes: 40960000, totalElements: 10240000 }
2021-10-13 07:53:36 DATA:  db loaded: { existingRecords: 0, newRecords: 5700 }
2021-10-13 07:53:36 INFO:  starting worker thread pool: { totalWorkers: 6, alreadyActive: 0 }
2021-10-13 07:53:36 STATE: submitted: { matchJobs: 100, poolSize: 6, activeWorkers: 6 }
2021-10-13 07:53:38 STATE: { matchJobsFinished: 100, totalTimeMs: 1769, averageTimeMs: 17.69 }
2021-10-13 07:53:38 INFO:  closing workers: { poolSize: 6, activeWorkers: 6 }