Prevent bad effects of zero search time.

4 files changed, 23 insertions, 13 deletions

diff --git a/searchcore/src/tests/fdispatch/randomrow/randomrow_test.cpp b/searchcore/src/tests/fdispatch/randomrow/randomrow_test.cpp
index 41db91035ed..c6791436bff 100644
--- a/searchcore/src/tests/fdispatch/randomrow/randomrow_test.cpp
+++ b/searchcore/src/tests/fdispatch/randomrow/randomrow_test.cpp
@@ -16,25 +16,29 @@ TEST("requireThatEmpyStateReturnsRowZero")
 
 TEST("requireThatDecayWorks")
 {
-    constexpr double SMALL = 0.000001;
+    constexpr double SMALL = 0.00001;
     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_APPROX(1.5, s.getRowState(0).getAverageSearchTime(), SMALL);
+    EXPECT_APPROX(1.02326, s.getRowState(0).getAverageSearchTime(), SMALL);
     s.updateSearchTime(2.0, 0);
-    EXPECT_APPROX(1.666667, s.getRowState(0).getAverageSearchTime(), SMALL);
+    EXPECT_APPROX(1.04545, 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(0.771429, s.getRowState(0).getAverageSearchTime(), SMALL);
+    EXPECT_APPROX(0.966667, 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);
+    for (size_t i(0); i < 10000; i++) {
+        s.updateSearchTime(0.0, 0);
+    }
+    EXPECT_APPROX(0.001045, s.getRowState(0).getAverageSearchTime(), SMALL);
 }
 
 TEST("requireWeightedSelectionWorks")
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.cpp b/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.cpp
index 4e1bc62b790..cd68b208ff4 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.cpp
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/plain_dataset.cpp
@@ -195,7 +195,7 @@ FastS_PlainDataSet::FastS_PlainDataSet(FastS_AppContext *appCtx,
                                        FastS_DataSetDesc *desc)
     : FastS_DataSetBase(appCtx, desc),
       _partMap(desc),
-      _stateOfRows(_partMap.getNumRows(), 0.010, desc->GetQueryDistributionMode().getLatencyDecayRate()),
+      _stateOfRows(_partMap.getNumRows(), 0.001, desc->GetQueryDistributionMode().getLatencyDecayRate()),
       _MHPN_log(),
       _slowQueryLimitFactor(desc->GetSlowQueryLimitFactor()),
       _slowQueryLimitBias(desc->GetSlowQueryLimitBias()),
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.cpp b/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.cpp
index b0ca9f3463b..b11d9aeac53 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.cpp
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.cpp
@@ -4,11 +4,22 @@
 
 namespace fdispatch {
 
+constexpr uint64_t MIN_DECAY_RATE = 42;
+constexpr double MIN_QUERY_TIME = 0.001;
+
+RowState::RowState(double initialValue, uint64_t decayRate) :
+    _decayRate(std::max(decayRate, MIN_DECAY_RATE)),
+    _avgSearchTime(std::max(initialValue, MIN_QUERY_TIME)),
+    _sumActiveDocs(0),
+    _numQueries(0)
+{ }
+
 void RowState::updateSearchTime(double searchTime)
 {
-    _numQueries++;
-    double decayRate = std::min(_numQueries, _decayRate);
+    searchTime = std::max(searchTime, MIN_QUERY_TIME);
+    double decayRate = std::min(_numQueries + MIN_DECAY_RATE, _decayRate);
     _avgSearchTime = (searchTime + (decayRate-1)*_avgSearchTime)/decayRate;
+    ++_numQueries;
 }
 
 StateOfRows::StateOfRows(size_t numRows, double initialValue, uint64_t decayRate) :
diff --git a/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.h b/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.h
index 00bf7f1bd91..92268a291bb 100644
--- a/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.h
+++ b/searchcore/src/vespa/searchcore/fdispatch/search/rowstate.h
@@ -15,12 +15,7 @@ namespace fdispatch {
  **/
 class RowState {
 public:
-    RowState(double initialValue, uint64_t decayRate) :
-        _decayRate(std::max(1ul, decayRate)),
-        _avgSearchTime(initialValue),
-        _sumActiveDocs(0),
-        _numQueries(0)
-    { }
+    RowState(double initialValue, uint64_t decayRate);
     double getAverageSearchTime() const { return _avgSearchTime; }
     double getAverageSearchTimeInverse() const { return 1.0/_avgSearchTime; }
     void updateSearchTime(double searchTime);