Class: Split::Experiment

Inherits:
Object
  • Object
show all
Defined in:
lib/split/experiment.rb

Constant Summary collapse

DEFAULT_OPTIONS =
{
  :resettable => true
}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, options = {}) ⇒ Experiment

Returns a new instance of Experiment.



16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
# File 'lib/split/experiment.rb', line 16

def initialize(name, options = {})
  options = DEFAULT_OPTIONS.merge(options)

  @name = name.to_s

  alternatives = extract_alternatives_from_options(options)

  if alternatives.empty? && (exp_config = Split.configuration.experiment_for(name))
    options = {
      alternatives: load_alternatives_from_configuration,
      goals: Split::GoalsCollection.new(@name).load_from_configuration,
      metadata: ,
      resettable: exp_config[:resettable],
      algorithm: exp_config[:algorithm]
    }
  else
    options[:alternatives] = alternatives
  end

  set_alternatives_and_options(options)
end

Instance Attribute Details

#alternative_probabilitiesObject

Returns the value of attribute alternative_probabilities.



6
7
8
# File 'lib/split/experiment.rb', line 6

def alternative_probabilities
  @alternative_probabilities
end

#alternativesObject

Returns the value of attribute alternatives.



9
10
11
# File 'lib/split/experiment.rb', line 9

def alternatives
  @alternatives
end

#goalsObject

Returns the value of attribute goals.



5
6
7
# File 'lib/split/experiment.rb', line 5

def goals
  @goals
end

#metadataObject

Returns the value of attribute metadata.



7
8
9
# File 'lib/split/experiment.rb', line 7

def 
  @metadata
end

#nameObject

Returns the value of attribute name.



4
5
6
# File 'lib/split/experiment.rb', line 4

def name
  @name
end

#resettableObject

Returns the value of attribute resettable.



10
11
12
# File 'lib/split/experiment.rb', line 10

def resettable
  @resettable
end

Class Method Details

.finished_key(key) ⇒ Object



38
39
40
# File 'lib/split/experiment.rb', line 38

def self.finished_key(key)
  "#{key}:finished"
end

Instance Method Details

#==(obj) ⇒ Object



111
112
113
# File 'lib/split/experiment.rb', line 111

def ==(obj)
  self.name == obj.name
end

#[](name) ⇒ Object



115
116
117
# File 'lib/split/experiment.rb', line 115

def [](name)
  alternatives.find{|a| a.name == name}
end

#algorithmObject



119
120
121
# File 'lib/split/experiment.rb', line 119

def algorithm
  @algorithm ||= Split.configuration.algorithm
end

#algorithm=(algorithm) ⇒ Object



123
124
125
# File 'lib/split/experiment.rb', line 123

def algorithm=(algorithm)
  @algorithm = algorithm.is_a?(String) ? algorithm.constantize : algorithm
end

#calc_alternative_probabilities(winning_counts, number_of_simulations) ⇒ Object



322
323
324
325
326
327
328
# File 'lib/split/experiment.rb', line 322

def calc_alternative_probabilities(winning_counts, number_of_simulations)
  alternative_probabilities = {}
  winning_counts.each do |alternative, wins|
    alternative_probabilities[alternative] = wins / number_of_simulations.to_f
  end
  return alternative_probabilities
end

#calc_beta_params(goal = nil) ⇒ Object



373
374
375
376
377
378
379
380
381
382
383
384
385
# File 'lib/split/experiment.rb', line 373

def calc_beta_params(goal = nil)
  beta_params = {}
  alternatives.each do |alternative|
    conversions = goal.nil? ? alternative.completed_count : alternative.completed_count(goal)
    alpha = 1 + conversions
    beta = 1 + alternative.participant_count - conversions

    params = [alpha, beta]

    beta_params[alternative] = params
  end
  return beta_params
end

#calc_simulated_conversion_rates(beta_params) ⇒ Object



355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
# File 'lib/split/experiment.rb', line 355

def calc_simulated_conversion_rates(beta_params)
  # initialize a random variable (from which to simulate conversion rates ~beta-distributed)
  rand = SimpleRandom.new
  rand.set_seed

  simulated_cr_hash = {}

  # create a hash which has the conversion rate pulled from each alternative's beta distribution
  beta_params.each do |alternative, params|
    alpha = params[0]
    beta = params[1]
    simulated_conversion_rate = rand.beta(alpha, beta)
    simulated_cr_hash[alternative] = simulated_conversion_rate
  end

  return simulated_cr_hash
end

#calc_timeObject



391
392
393
# File 'lib/split/experiment.rb', line 391

def calc_time
  redis.hget(experiment_config_key, :calc_time).to_i
end

#calc_time=(time) ⇒ Object



387
388
389
# File 'lib/split/experiment.rb', line 387

def calc_time=(time)
  redis.hset(experiment_config_key, :calc_time, time)
end

#calc_winning_alternativesObject



271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
# File 'lib/split/experiment.rb', line 271

def calc_winning_alternatives
  # Cache the winning alternatives so we recalculate them once per the specified interval.
  intervals_since_epoch =
    Time.now.utc.to_i / Split.configuration.winning_alternative_recalculation_interval

  if self.calc_time != intervals_since_epoch
    if goals.empty?
      self.estimate_winning_alternative
    else
      goals.each do |goal|
        self.estimate_winning_alternative(goal)
      end
    end

    self.calc_time = intervals_since_epoch

    self.save
  end
end

#controlObject



164
165
166
# File 'lib/split/experiment.rb', line 164

def control
  alternatives.first
end

#count_simulated_wins(winning_alternatives) ⇒ Object



330
331
332
333
334
335
336
337
338
339
340
341
# File 'lib/split/experiment.rb', line 330

def count_simulated_wins(winning_alternatives)
   # initialize a hash to keep track of winning alternative in simulations
  winning_counts = {}
  alternatives.each do |alternative|
    winning_counts[alternative] = 0
  end
  # count number of times each alternative won, calculate probabilities, place in hash
  winning_alternatives.each do |alternative|
    winning_counts[alternative] += 1
  end
  return winning_counts
end

#deleteObject



241
242
243
244
245
246
247
248
249
250
251
# File 'lib/split/experiment.rb', line 241

def delete
  Split.configuration.on_before_experiment_delete.call(self)
  if Split.configuration.start_manually
    redis.hdel(:experiment_start_times, @name)
  end
  reset_winner
  redis.srem(:experiments, name)
  remove_experiment_configuration
  Split.configuration.on_experiment_delete.call(self)
  increment_version
end

#delete_metadataObject



253
254
255
# File 'lib/split/experiment.rb', line 253

def 
  redis.del()
end

#estimate_winning_alternative(goal = nil) ⇒ Object



291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
# File 'lib/split/experiment.rb', line 291

def estimate_winning_alternative(goal = nil)
  # initialize a hash of beta distributions based on the alternatives' conversion rates
  beta_params = calc_beta_params(goal)

  winning_alternatives = []

  Split.configuration.beta_probability_simulations.times do
    # calculate simulated conversion rates from the beta distributions
    simulated_cr_hash = calc_simulated_conversion_rates(beta_params)

    winning_alternative = find_simulated_winner(simulated_cr_hash)

    # push the winning pair to the winning_alternatives array
    winning_alternatives.push(winning_alternative)
  end

  winning_counts = count_simulated_wins(winning_alternatives)

  @alternative_probabilities = calc_alternative_probabilities(winning_counts, Split.configuration.beta_probability_simulations)

  write_to_alternatives(goal)

  self.save
end

#extract_alternatives_from_options(options) ⇒ Object



54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
# File 'lib/split/experiment.rb', line 54

def extract_alternatives_from_options(options)
  alts = options[:alternatives] || []

  if alts.length == 1
    if alts[0].is_a? Hash
      alts = alts[0].map{|k,v| {k => v} }
    end
  end

  if alts.empty?
    exp_config = Split.configuration.experiment_for(name)
    if exp_config
      alts = load_alternatives_from_configuration
      options[:goals] = Split::GoalsCollection.new(@name).load_from_configuration
      options[:metadata] = 
      options[:resettable] = exp_config[:resettable]
      options[:algorithm] = exp_config[:algorithm]
    end
  end

  options[:alternatives] = alts

  set_alternatives_and_options(options)

  # calculate probability that each alternative is the winner
  @alternative_probabilities = {}
  alts
end

#find_simulated_winner(simulated_cr_hash) ⇒ Object



343
344
345
346
347
348
349
350
351
352
353
# File 'lib/split/experiment.rb', line 343

def find_simulated_winner(simulated_cr_hash)
  # figure out which alternative had the highest simulated conversion rate
  winning_pair = ["",0.0]
  simulated_cr_hash.each do |alternative, rate|
    if rate > winning_pair[1]
      winning_pair = [alternative, rate]
    end
  end
  winner = winning_pair[0]
  return winner
end

#finished_keyObject



221
222
223
# File 'lib/split/experiment.rb', line 221

def finished_key
  self.class.finished_key(key)
end

#goals_keyObject



217
218
219
# File 'lib/split/experiment.rb', line 217

def goals_key
  "#{name}:goals"
end

#has_winner?Boolean

Returns:

  • (Boolean)


150
151
152
153
# File 'lib/split/experiment.rb', line 150

def has_winner?
  return @has_winner if defined? @has_winner
  @has_winner = !winner.nil?
end

#increment_versionObject



205
206
207
# File 'lib/split/experiment.rb', line 205

def increment_version
  @version = redis.incr("#{name}:version")
end

#jstring(goal = nil) ⇒ Object



395
396
397
398
399
400
401
402
# File 'lib/split/experiment.rb', line 395

def jstring(goal = nil)
  js_id = if goal.nil?
            name
          else
            name + "-" + goal
          end
  js_id.gsub('/', '--')
end

#keyObject



209
210
211
212
213
214
215
# File 'lib/split/experiment.rb', line 209

def key
  if version.to_i > 0
    "#{name}:#{version}"
  else
    name
  end
end

#load_from_redisObject



257
258
259
260
261
262
263
264
265
266
267
268
269
# File 'lib/split/experiment.rb', line 257

def load_from_redis
  exp_config = redis.hgetall(experiment_config_key)

  options = {
    resettable: exp_config['resettable'],
    algorithm: exp_config['algorithm'],
    alternatives: load_alternatives_from_redis,
    goals: Split::GoalsCollection.new(@name).load_from_redis,
    metadata: 
  }

  set_alternatives_and_options(options)
end

#metadata_keyObject



225
226
227
# File 'lib/split/experiment.rb', line 225

def 
  "#{name}:metadata"
end

#new_record?Boolean

Returns:

  • (Boolean)


107
108
109
# File 'lib/split/experiment.rb', line 107

def new_record?
  !redis.exists(name)
end

#next_alternativeObject



189
190
191
# File 'lib/split/experiment.rb', line 189

def next_alternative
  winner || random_alternative
end

#participant_countObject



160
161
162
# File 'lib/split/experiment.rb', line 160

def participant_count
  alternatives.inject(0){|sum,a| sum + a.participant_count}
end

#random_alternativeObject



193
194
195
196
197
198
199
# File 'lib/split/experiment.rb', line 193

def random_alternative
  if alternatives.length > 1
    algorithm.choose_alternative(self)
  else
    alternatives.first
  end
end

#resetObject



233
234
235
236
237
238
239
# File 'lib/split/experiment.rb', line 233

def reset
  Split.configuration.on_before_experiment_reset.call(self)
  alternatives.each(&:reset)
  reset_winner
  Split.configuration.on_experiment_reset.call(self)
  increment_version
end

#reset_winnerObject



168
169
170
171
# File 'lib/split/experiment.rb', line 168

def reset_winner
  redis.hdel(:experiment_winner, name)
  @has_winner = false
end

#resettable?Boolean

Returns:

  • (Boolean)


229
230
231
# File 'lib/split/experiment.rb', line 229

def resettable?
  resettable
end

#saveObject



83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
# File 'lib/split/experiment.rb', line 83

def save
  validate!

  if new_record?
    start unless Split.configuration.start_manually
    persist_experiment_configuration
  elsif experiment_configuration_has_changed?
    reset unless Split.configuration.reset_manually
    persist_experiment_configuration
  end

  redis.hset(experiment_config_key, :resettable, resettable)
  redis.hset(experiment_config_key, :algorithm, algorithm.to_s)
  self
end

#set_alternatives_and_options(options) ⇒ Object



42
43
44
45
46
47
48
49
50
51
52
# File 'lib/split/experiment.rb', line 42

def set_alternatives_and_options(options)
  options_with_defaults = DEFAULT_OPTIONS.merge(
    options.reject { |k, v| v.nil? }
  )

  self.alternatives = options_with_defaults[:alternatives]
  self.goals = options_with_defaults[:goals]
  self.resettable = options_with_defaults[:resettable]
  self.algorithm = options_with_defaults[:algorithm]
  self. = options_with_defaults[:metadata]
end

#startObject



173
174
175
# File 'lib/split/experiment.rb', line 173

def start
  redis.hset(:experiment_start_times, @name, Time.now.to_i)
end

#start_timeObject



177
178
179
180
181
182
183
184
185
186
187
# File 'lib/split/experiment.rb', line 177

def start_time
  t = redis.hget(:experiment_start_times, @name)
  if t
    # Check if stored time is an integer
    if t =~ /^[-+]?[0-9]+$/
      Time.at(t.to_i)
    else
      Time.parse(t)
    end
  end
end

#validate!Object



99
100
101
102
103
104
105
# File 'lib/split/experiment.rb', line 99

def validate!
  if @alternatives.empty? && Split.configuration.experiment_for(@name).nil?
    raise ExperimentNotFound.new("Experiment #{@name} not found")
  end
  @alternatives.each {|a| a.validate! }
  goals_collection.validate!
end

#versionObject



201
202
203
# File 'lib/split/experiment.rb', line 201

def version
  @version ||= (redis.get("#{name}:version").to_i || 0)
end

#winnerObject



141
142
143
144
145
146
147
148
# File 'lib/split/experiment.rb', line 141

def winner
  experiment_winner = redis.hget(:experiment_winner, name)
  if experiment_winner
    Split::Alternative.new(experiment_winner, name)
  else
    nil
  end
end

#winner=(winner_name) ⇒ Object



155
156
157
158
# File 'lib/split/experiment.rb', line 155

def winner=(winner_name)
  redis.hset(:experiment_winner, name, winner_name.to_s)
  @has_winner = true
end

#write_to_alternatives(goal = nil) ⇒ Object



316
317
318
319
320
# File 'lib/split/experiment.rb', line 316

def write_to_alternatives(goal = nil)
  alternatives.each do |alternative|
    alternative.set_p_winner(@alternative_probabilities[alternative], goal)
  end
end