diff options
| -rw-r--r-- | base/field_trial.cc | 11 | ||||
| -rw-r--r-- | base/field_trial.h | 8 | ||||
| -rw-r--r-- | base/field_trial_unittest.cc | 21 |
3 files changed, 33 insertions, 7 deletions
diff --git a/base/field_trial.cc b/base/field_trial.cc index 549822f..2b354d7 100644 --- a/base/field_trial.cc +++ b/base/field_trial.cc @@ -1,4 +1,4 @@ -// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved. +// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. @@ -36,10 +36,15 @@ FieldTrial::FieldTrial(const std::string& name, int FieldTrial::AppendGroup(const std::string& name, Probability group_probability) { DCHECK(group_probability <= divisor_); - accumulated_group_probability_ += group_probability; + DCHECK(group_probability >=0 || + group_probability == kAllRemainingProbability); + if (group_probability == kAllRemainingProbability) + accumulated_group_probability_ = divisor_; + else + accumulated_group_probability_ += group_probability; DCHECK(accumulated_group_probability_ <= divisor_); if (group_ == kNotParticipating && accumulated_group_probability_ > random_) { - // This is the group that crossed the random line, so we do teh assignment. + // This is the group that crossed the random line, so we do the assignment. group_ = next_group_number_; if (name.empty()) StringAppendF(&group_name_, "_%d", group_); diff --git a/base/field_trial.h b/base/field_trial.h index 6d3c101..fba0b01 100644 --- a/base/field_trial.h +++ b/base/field_trial.h @@ -1,4 +1,4 @@ -// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved. +// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. @@ -50,7 +50,7 @@ // "MemoryExperiment").data(), count); // The above code will create 3 distinct histograms, with each run of the -// application being assigned to of of teh three groups, and for each group, the +// application being assigned to of of the three groups, and for each group, the // correspondingly named histogram will be populated: // Memory.RendererTotal // 96% of users still fill this histogram. @@ -80,7 +80,9 @@ class FieldTrial : public base::RefCounted<FieldTrial> { // Provide an easy way to assign all remaining probability to a group. Note // that this will force an instance to participate, and make it illegal to - // attempt to probabalistically add any other groups to the trial. + // attempt to probabalistically add any other groups to the trial. When doing + // A/B tests with timings, it is often best to define all groups, so that + // histograms will get unique names via the MakeName() methods. static const Probability kAllRemainingProbability; // The name is used to register the instance with the FieldTrialList class, diff --git a/base/field_trial_unittest.cc b/base/field_trial_unittest.cc index 59d8e15..430fd67 100644 --- a/base/field_trial_unittest.cc +++ b/base/field_trial_unittest.cc @@ -1,4 +1,4 @@ -// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved. +// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. @@ -69,6 +69,25 @@ TEST_F(FieldTrialTest, AbsoluteProbabilities) { } } +TEST_F(FieldTrialTest, RemainingProbability) { + // First create a test that hasn't had a winner yet. + const std::string winner = "Winner"; + const std::string loser = "Loser"; + scoped_refptr<FieldTrial> trial; + int counter = 0; + do { + std::string name = StringPrintf("trial%d", ++counter); + trial = new FieldTrial(name, 10); + trial->AppendGroup(loser, 5); // 50% chance of not being chosen. + } while (trial->group() != FieldTrial::kNotParticipating); + + // Now add a winner with all remaining probability. + trial->AppendGroup(winner, FieldTrial::kAllRemainingProbability); + + // And that winner should ALWAYS win. + EXPECT_EQ(winner, trial->group_name()); +} + TEST_F(FieldTrialTest, MiddleProbabilities) { char name[] = " same name"; bool false_event_seen = false; |