Log suggestion scores in 10 discrete buckets.

components/ntp_snippets/content_suggestions_metrics.cc

 // Copyright 2016 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.
 
 #include "components/ntp_snippets/content_suggestions_metrics.h"
 
+#include <cmath>
 #include <string>
 #include <type_traits>
 
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/user_metrics.h"
 #include "base/strings/stringprintf.h"
 #include "base/template_util.h"
 
 namespace ntp_snippets {
 namespace metrics {
 
 namespace {
 
 const int kMaxSuggestionsPerCategory = 10;
 const int kMaxSuggestionsTotal = 50;
 
 const char kHistogramCountOnNtpOpened[] =
     "NewTabPage.ContentSuggestions.CountOnNtpOpened";
 const char kHistogramShown[] = "NewTabPage.ContentSuggestions.Shown";
 const char kHistogramShownAge[] = "NewTabPage.ContentSuggestions.ShownAge";
-const char kHistogramShownScore[] = "NewTabPage.ContentSuggestions.ShownScore";
+const char kHistogramShownScore[] =
+    "NewTabPage.ContentSuggestions.ShownScoreNormalized";
 const char kHistogramOpened[] = "NewTabPage.ContentSuggestions.Opened";
 const char kHistogramOpenedAge[] = "NewTabPage.ContentSuggestions.OpenedAge";
 const char kHistogramOpenedScore[] =
-    "NewTabPage.ContentSuggestions.OpenedScore";
+    "NewTabPage.ContentSuggestions.OpenedScoreNormalized";
 const char kHistogramOpenDisposition[] =
     "NewTabPage.ContentSuggestions.OpenDisposition";
 const char kHistogramMenuOpened[] = "NewTabPage.ContentSuggestions.MenuOpened";
 const char kHistogramMenuOpenedAge[] =
     "NewTabPage.ContentSuggestions.MenuOpenedAge";
 const char kHistogramMenuOpenedScore[] =
-    "NewTabPage.ContentSuggestions.MenuOpenedScore";
+    "NewTabPage.ContentSuggestions.MenuOpenedScoreNormalized";
 const char kHistogramDismissedUnvisited[] =
     "NewTabPage.ContentSuggestions.DismissedUnvisited";
 const char kHistogramDismissedVisited[] =
     "NewTabPage.ContentSuggestions.DismissedVisited";
 const char kHistogramArticlesUsageTimeLocal[] =
     "NewTabPage.ContentSuggestions.UsageTimeLocal";
 const char kHistogramVisitDuration[] =
     "NewTabPage.ContentSuggestions.VisitDuration";
 const char kHistogramMoreButtonShown[] =
     "NewTabPage.ContentSuggestions.MoreButtonShown";
@@ skipping 111 matching lines @@
 void UmaHistogramAge(const std::string& name, const base::TimeDelta& value) {
   base::Histogram::FactoryTimeGet(
       name, base::TimeDelta::FromSeconds(1), base::TimeDelta::FromDays(7), 100,
       base::HistogramBase::kUmaTargetedHistogramFlag)
       ->AddTime(value);
 }
 
 // This corresponds to UMA_HISTOGRAM_CUSTOM_COUNTS (with min/max appropriate
 // for the score of suggestions) for use with dynamic histogram names.
 void UmaHistogramScore(const std::string& name, float value) {
-  base::Histogram::FactoryGet(name, 1, 100000, 50,
-                              base::HistogramBase::kUmaTargetedHistogramFlag)
-      ->Add(value);
+  // Scores are typically reported in a range of (0,1]. As UMA does not support
+  // floats, we put them on a discrete scale of [1,10]. We keep the extra bucket
+  // 11 for unexpected over-flows as we want to distinguish them from scores
+  // close to 1. For instance, the discrete value 1 represents score values
+  // within (0.0, 0.1].
+  base::LinearHistogram::FactoryGet(
+      name, 1, 11, 12, base::HistogramBase::kUmaTargetedHistogramFlag)
+      ->Add(ceil(value * 10));

[Alexei Svitkine (slow), 2017/01/12 18:42:04]

Can you use UmaHistogramExactLinear() here?

[tschumann, 2017/01/13 17:57:23]

Yes. That's actually nice! Turns out UmaHistogramLongTimes() already exists
there too (I could use another pair of eyes double-checking they are indeed
identical).

 }
 
 void LogCategoryHistogramEnumeration(const char* base_name,
                                      Category category,
                                      int value,
                                      int boundary_value) {
   std::string name = GetCategoryHistogramName(base_name, category);
   // Since the histogram name is dynamic, we can't use the regular macro.
   UmaHistogramEnumeration(name, value, boundary_value);
 }
@@ skipping 179 matching lines @@
 }
 
 void OnCategoryDismissed(Category category) {
   UMA_HISTOGRAM_ENUMERATION(kHistogramCategoryDismissed,
                             static_cast<int>(GetHistogramCategory(category)),
                             static_cast<int>(HistogramCategories::COUNT));
 }
 
 }  // namespace metrics
 }  // namespace ntp_snippets