Created
December 11, 2013 00:35
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Measure the times it takes to access (hit and miss) elements in hashes with up to 2^21 elements.
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| require 'benchmark' | |
| require 'ascii_charts' | |
| def measure | |
| GC.disable | |
| Benchmark.realtime do | |
| yield | |
| end | |
| ensure | |
| GC.enable | |
| end | |
| def measure_hash_accesses(exp, count, miss = false) | |
| exp.times.map do |exponent| | |
| size = 2**exponent | |
| hash = {} | |
| (1..size).each do |n| | |
| index = rand | |
| hash[index] = rand | |
| end | |
| keys = hash.keys | |
| kick = miss ? 1.0 : 0.0 | |
| targets = count.times.map { keys.sample + kick } | |
| offset = measure do | |
| targets.each do |k| | |
| val = k | |
| end | |
| end | |
| access_time = measure do | |
| targets.each do |k| | |
| val = hash[k] | |
| end | |
| end | |
| [size, access_time - offset] | |
| end | |
| end | |
| def draw(title, times) | |
| puts AsciiCharts::Cartesian.new( | |
| times, | |
| title: title, | |
| y_step_size: 0.05, | |
| max_y_vals: 1.0, | |
| bar: true, | |
| hide_zero: true | |
| ).draw | |
| end | |
| count = 1_000_000 | |
| hit_times = measure_hash_accesses(21, count) | |
| draw "#{count} successful hash reads", hit_times | |
| miss_times = measure_hash_accesses(21, count, true) | |
| draw "#{count} missing hash reads", miss_times |
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