Moving RandomSample to base.

base/base.pro

@@ -18,6 +18,7 @@ SOURCES += \
     logging.cpp \
     lower_case.cpp \
     normalize_unicode.cpp \
+    random.cpp \
     shared_buffer_manager.cpp \
     src_point.cpp \
     string_format.cpp \
@@ -59,6 +60,7 @@ HEADERS += \
     mutex.hpp \
     newtype.hpp \
     observer_list.hpp \
+    random.hpp \
     range_iterator.hpp \
     ref_counted.hpp \
     regexp.hpp \

base/random.cpp

@@ -0,0 +1,22 @@
+#include "base/random.hpp"
+
+#include <algorithm>
+#include <numeric>
+
+namespace my
+{
+std::vector<size_t> RandomSample(size_t n, size_t k, std::minstd_rand & rng)
+{
+  std::vector<size_t> result(std::min(k, n));
+  std::iota(result.begin(), result.end(), 0);
+
+  for (size_t i = k; i < n; ++i)
+  {
+    size_t const j = rng() % (i + 1);
+    if (j < k)
+      result[j] = i;
+  }
+
+  return result;
+}
+}  // my

base/random.hpp

@@ -0,0 +1,9 @@
+#pragma once
+
+#include <random>
+#include <vector>
+
+namespace my
+{
+std::vector<size_t> RandomSample(size_t n, size_t k, std::minstd_rand & rng);
+}  // my

search/pre_ranker.cpp

@@ -9,6 +9,7 @@
 #include "indexer/rank_table.hpp"
 #include "indexer/scales.hpp"
 
+#include "base/random.hpp"
 #include "base/stl_helpers.hpp"
 
 #include "std/iterator.hpp"
@@ -46,22 +47,6 @@ struct ComparePreResult1
   }
 };
 
-// Selects a fair random subset of size min(|n|, |k|) from [0, 1, 2, ..., n - 1].
-vector<size_t> RandomSample(size_t n, size_t k, minstd_rand & rng)
-{
-  vector<size_t> result(std::min(k, n));
-  iota(result.begin(), result.end(), 0);
-
-  for (size_t i = k; i < n; ++i)
-  {
-    size_t const j = rng() % (i + 1);
-    if (j < k)
-      result[j] = i;
-  }
-
-  return result;
-}
-
 void SweepNearbyResults(double eps, vector<PreResult1> & results)
 {
   NearbyPointsSweeper sweeper(eps);
@@ -281,7 +266,7 @@ void PreRanker::FilterForViewportSearch()
 
     if (m <= old)
     {
-      for (size_t i : RandomSample(old, m, m_rng))
+      for (size_t i : my::RandomSample(old, m, m_rng))
         results.push_back(m_results[bucket[i]]);
     }
     else
@@ -289,7 +274,7 @@ void PreRanker::FilterForViewportSearch()
       for (size_t i = 0; i < old; ++i)
         results.push_back(m_results[bucket[i]]);
 
-      for (size_t i : RandomSample(bucket.size() - old, m - old, m_rng))
+      for (size_t i : my::RandomSample(bucket.size() - old, m - old, m_rng))
         results.push_back(m_results[bucket[old + i]]);
     }
   }
@@ -301,7 +286,7 @@ void PreRanker::FilterForViewportSearch()
   else
   {
     m_results.clear();
-    for (size_t i : RandomSample(results.size(), BatchSize(), m_rng))
+    for (size_t i : my::RandomSample(results.size(), BatchSize(), m_rng))
       m_results.push_back(results[i]);
   }
 }