Allow faster converge on startup, by capping decay rate at queries issued so far.

3 files changed, 23 insertions, 12 deletions

diff --git a/searchcore/src/tests/fdispatch/randomrow/randomrow_test.cpp b/searchcore/src/tests/fdispatch/randomrow/randomrow_test.cpp
index 217e994980b..41db91035ed 100644
--- a/searchcore/src/tests/fdispatch/randomrow/randomrow_test.cpp
+++ b/searchcore/src/tests/fdispatch/randomrow/randomrow_test.cpp
@@ -16,18 +16,25 @@ TEST("requireThatEmpyStateReturnsRowZero")
 
 TEST("requireThatDecayWorks")
 {
+    constexpr double SMALL = 0.000001;
     StateOfRows s(1, 1.0, 1000);
     s.updateSearchTime(1.0, 0);
     EXPECT_EQUAL(1.0, s.getRowState(0).getAverageSearchTime());
     s.updateSearchTime(2.0, 0);
-    EXPECT_EQUAL(1.001, s.getRowState(0).getAverageSearchTime());
+    EXPECT_APPROX(1.5, s.getRowState(0).getAverageSearchTime(), SMALL);
     s.updateSearchTime(2.0, 0);
-    EXPECT_APPROX(1.002, s.getRowState(0).getAverageSearchTime(), 0.0001);
+    EXPECT_APPROX(1.666667, s.getRowState(0).getAverageSearchTime(), SMALL);
     s.updateSearchTime(0.1, 0);
     s.updateSearchTime(0.1, 0);
     s.updateSearchTime(0.1, 0);
     s.updateSearchTime(0.1, 0);
-    EXPECT_APPROX(0.998396, s.getRowState(0).getAverageSearchTime(), 0.000001);
+    EXPECT_APPROX(0.771429, s.getRowState(0).getAverageSearchTime(), SMALL);
+    for (size_t i(0); i < 10000; i++) {
+        s.updateSearchTime(1.0, 0);
+    }
+    EXPECT_APPROX(1.0, s.getRowState(0).getAverageSearchTime(), SMALL);
+    s.updateSearchTime(0.1, 0);
+    EXPECT_APPROX(0.9991, s.getRowState(0).getAverageSearchTime(), SMALL);
 }
 
 TEST("requireWeightedSelectionWorks")
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.cpp b/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.cpp
index c4b0319e6cb..73c0afe6bc6 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.cpp
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.cpp
@@ -6,10 +6,12 @@ namespace fdispatch {
 
 void RowState::updateSearchTime(double searchTime)
 {
-    _avgSearchTime = (searchTime + (_decayRate-1)*_avgSearchTime)/_decayRate;
+    _numQueries++;
+    double decayRate = std::max(1ul, std::min(_numQueries, _decayRate));
+    _avgSearchTime = (searchTime + (decayRate-1)*_avgSearchTime)/decayRate;
 }
 
-StateOfRows::StateOfRows(size_t numRows, double initialValue, double decayRate) :
+StateOfRows::StateOfRows(size_t numRows, double initialValue, uint64_t decayRate) :
    _rows(numRows, RowState(initialValue, decayRate)),
    _sumActiveDocs(0), _invalidActiveDocsCounter(0)
 {
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.h b/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.h
index 07bc769cfdd..f8c05fe2707 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.h
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.h
@@ -15,10 +15,11 @@ namespace fdispatch {
  **/
 class RowState {
 public:
-    RowState(double initialValue, double decayRate) :
+    RowState(double initialValue, uint64_t decayRate) :
         _avgSearchTime(initialValue),
         _decayRate(decayRate),
-        _sumActiveDocs(0)
+        _sumActiveDocs(0),
+        _numQueries(0)
     { }
     double getAverageSearchTime() const { return _avgSearchTime; }
     double getAverageSearchTimeInverse() const { return 1.0/_avgSearchTime; }
@@ -30,9 +31,10 @@ public:
         _sumActiveDocs = tmp;
     }
 private:
-    double _avgSearchTime;
-    double _decayRate;
+    double   _avgSearchTime;
+    uint64_t _decayRate;
     uint64_t _sumActiveDocs;
+    uint64_t _numQueries;
 };
 
 /**
@@ -43,7 +45,7 @@ private:
  **/
 class StateOfRows {
 public:
-    StateOfRows(size_t numRows, double initial, double decayRate);
+    StateOfRows(size_t numRows, double initial, uint64_t decayRate);
     void updateSearchTime(double searchTime, uint32_t rowId);
     const RowState & getRowState(uint32_t rowId) const { return _rows[rowId]; }
     RowState & getRowState(uint32_t rowId) { return _rows[rowId]; }
@@ -56,8 +58,8 @@ public:
     bool activeDocsValid() const { return _invalidActiveDocsCounter == 0; }
 private:
     std::vector<RowState> _rows;
-    uint64_t _sumActiveDocs;
-    size_t _invalidActiveDocsCounter;
+    uint64_t              _sumActiveDocs;
+    size_t                _invalidActiveDocsCounter;
 };
 
 }