Benchmark "sigfigs" parameter to BigDecimal constructor given a Float

bench_bigdecimal_from_float.rb

require "benchmark/ips"
require "bigdecimal"

FLOATS = [1.35, 2.35, 3.35, 4.35, 5.35, 6.35, 7.35].freeze
STRINGS = ["1.4", "2.4", "3.4", "4.4", "5.4", "6.4", "7.4"].freeze

FULL = BigDecimal.double_fig
PART = 3

def full_precision
  FLOATS.map { |f| BigDecimal.new(f, FULL).round(1).to_f.to_s }
end	

def part_precision
  FLOATS.map { |f| BigDecimal.new(f, PART).round(1).to_f.to_s }
end

raise "Rounding failure on full precision" unless full_precision == STRINGS
raise "Rounding failure on part precision" unless part_precision == STRINGS

Benchmark.ips do |x|
  x.report('BigDecimal.new(f, BigDecimal.double_figs)') { full_precision }
  x.report('BigDecimal.new(f, 3                     )') { part_precision }
  x.compare!
end

output.txt

$ ruby bench_bigdecimal_from_float.rb
Warming up --------------------------------------
BigDecimal.new(f, BigDecimal.double_figs)
                         2.577k i/100ms
BigDecimal.new(f, 3                     )
                         2.663k i/100ms
Calculating -------------------------------------
BigDecimal.new(f, BigDecimal.double_figs)
                         25.596k (± 4.6%) i/s -    128.850k in   5.045449s
BigDecimal.new(f, 3                     )
                         25.137k (± 7.3%) i/s -    125.161k in   5.007108s

Comparison:
BigDecimal.new(f, BigDecimal.double_figs):    25595.8 i/s
BigDecimal.new(f, 3                     ):    25137.0 i/s - same-ish: difference falls within error