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_functions.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 80 matching lines @@
   return std::string();
 }
 
 std::string GetCategoryHistogramName(const char* base_name, Category category) {
   return base::StringPrintf(kPerCategoryHistogramFormat, base_name,
                             GetCategorySuffix(category).c_str());
 }
 
 // This corresponds to UMA_HISTOGRAM_ENUMERATION, for use with dynamic histogram
 // names.
 void UmaHistogramEnumeration(const std::string& name,

[Alexei Svitkine (slow), 2017/01/13 18:40:00]

Can this be removed too?

[tschumann, 2017/01/16 11:21:50]

yes -- thanks for calling that out! Turned out we abused them quite a bit.
Changed most callers to use the ExactLinear counter parts.

                              int value,
                              int boundary_value) {
   base::LinearHistogram::FactoryGet(
       name, 1, boundary_value, boundary_value + 1,
       base::HistogramBase::kUmaTargetedHistogramFlag)
       ->Add(value);
 }
 
-// This corresponds to UMA_HISTOGRAM_LONG_TIMES for use with dynamic histogram
-// names.
-void UmaHistogramLongTimes(const std::string& name,
-                           const base::TimeDelta& value) {
-  base::Histogram::FactoryTimeGet(
-      name, base::TimeDelta::FromMilliseconds(1), base::TimeDelta::FromHours(1),
-      50, base::HistogramBase::kUmaTargetedHistogramFlag)
-      ->AddTime(value);
-}
-
 // This corresponds to UMA_HISTOGRAM_CUSTOM_TIMES (with min/max appropriate
 // for the age of suggestions) for use with dynamic histogram names.
 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::UmaHistogramExactLinear(name, ceil(value * 10), 11);
 }
 
 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);
 }
 
 void LogCategoryHistogramLongTimes(const char* base_name,
                                    Category category,
                                    const base::TimeDelta& value) {
   std::string name = GetCategoryHistogramName(base_name, category);
   // Since the histogram name is dynamic, we can't use the regular macro.
   UmaHistogramLongTimes(name, value);

[Alexei Svitkine (slow), 2017/01/13 18:40:00]

Prefix this with base:: ?

[tschumann, 2017/01/16 11:21:50]

Done. (ADL at it's best ;-)).

 }
 
 void LogCategoryHistogramAge(const char* base_name,
                              Category category,
                              const base::TimeDelta& value) {
   std::string name = GetCategoryHistogramName(base_name, category);
   // Since the histogram name is dynamic, we can't use the regular macro.
   UmaHistogramAge(name, value);
 }
 
@@ skipping 162 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