Fast Polylines

Implementation of the Google polyline algorithm : https://code.google.com/apis/maps/documentation/utilities/polylinealgorithm.html

Greatly inspired by Joshua Clayton gem : https://github.com/joshuaclayton/polylines

But an about 8x faster encoding and 10x faster decoding implementation (make benchmark on a MacBook pro 13 - 2,3 GHz Intel Core i5).

** ENCODING **

Warming up --------------------------------------
    Polylines encode   282.000  i/100ms
FastPolylines encode     2.339k i/100ms
Calculating -------------------------------------
    Polylines encode      3.024k (± 7.4%) i/s -     15.228k in   5.068950s
FastPolylines encode     24.562k (± 6.7%) i/s -    123.967k in   5.074793s

Comparison:
FastPolylines encode:    24561.8 i/s
    Polylines encode:     3023.6 i/s - 8.12x  slower


** DECODING **

Warming up --------------------------------------
    Polylines decode   125.000  i/100ms
FastPolylines decode     1.341k i/100ms
Calculating -------------------------------------
    Polylines decode      1.284k (± 9.7%) i/s -      6.375k in   5.023536s
FastPolylines decode     13.278k (±20.5%) i/s -     61.686k in   5.003858s

Comparison:
FastPolylines decode:    13278.0 i/s
    Polylines decode:     1284.3 i/s - 10.34x  slower

Install

gem install fast-polylines

or in Bundler:

gem "fast-polylines"

Usage

require 'fast-polylines'

FastPolylines::Encoder.encode([[38.5, -120.2], [40.7, -120.95], [43.252, -126.453]])
# "_p~iF~ps|U_ulLnnqC_mqNvxq`@"

FastPolylines::Decoder.decode("_p~iF~ps|U_ulLnnqC_mqNvxq`@")
# [[38.5, -120.2], [40.7, -120.95], [43.252, -126.453]]

Advanced usage

• With a different precision (default precision of 1e5) :

FastPolylines::Encoder.encode([[38.5, -120.2], [40.7, -120.95], [43.252, -126.453]], 1e6)
# "_izlhA~rlgdF_{geC~ywl@_kwzCn`{nI"

FastPolylines::Decoder.decode("_izlhA~rlgdF_{geC~ywl@_kwzCn`{nI", 1e6)
# [[38.5, -120.2], [40.7, -120.95], [43.252, -126.453]]

Run the Benchmark

You can run the benchmark with make benchmark.

License

Please see LICENSE