Use square root of points for normalized score. (#8572)

Author: isoos

app/lib/search/mem_index.dart

@@ -313,9 +313,15 @@ class InMemoryPackageIndex {
     _adjustedOverallScores = _documents.map((doc) {
       final downloadScore = doc.downloadScore ?? 0.0;
       final likeScore = doc.likeScore ?? 0.0;
-      final combinedScore = (downloadScore + likeScore) / 2;
-      final points = doc.grantedPoints / math.max(1, doc.maxPoints);
-      final overall = combinedScore * 0.5 + points * 0.5;
+      final popularityScore = (downloadScore + likeScore) / 2;
+
+      // prevent division by zero in case maxPoints is zero
+      final pointRatio = doc.grantedPoints / math.max(1, doc.maxPoints);
+      // force value between 0.0 and 1.0 in case we have bad points
+      // using square root to lower the differences between higher values
+      final pointScore = math.sqrt(math.max(0.0, math.min(1.0, pointRatio)));
+
+      final overall = popularityScore * 0.5 + pointScore * 0.5;
       doc.overallScore = overall;
       // adding a base score prevents later multiplication with zero
       return 0.4 + 0.6 * overall;

app/test/search/mem_index_test.dart

@@ -98,7 +98,7 @@ server.dart adds a small, prescriptive server (PicoServer) that can be configure
         'nameMatches': ['async'],
         'sdkLibraryHits': [],
         'packageHits': [
-          {'package': 'async', 'score': closeTo(0.65, 0.01)},
+          {'package': 'async', 'score': closeTo(0.71, 0.01)},
         ],
       });
     });
@@ -143,8 +143,8 @@ server.dart adds a small, prescriptive server (PicoServer) that can be configure
         'totalCount': 2,
         'sdkLibraryHits': [],
         'packageHits': [
+          {'package': 'async', 'score': closeTo(0.71, 0.01)},
           {'package': 'http', 'score': closeTo(0.69, 0.01)},
-          {'package': 'async', 'score': closeTo(0.65, 0.01)},
         ],
       });
     });
@@ -157,7 +157,7 @@ server.dart adds a small, prescriptive server (PicoServer) that can be configure
         'totalCount': 1,
         'sdkLibraryHits': [],
         'packageHits': [
-          {'package': 'async', 'score': closeTo(0.34, 0.01)},
+          {'package': 'async', 'score': closeTo(0.37, 0.01)},
         ],
       });
     });
@@ -183,7 +183,7 @@ server.dart adds a small, prescriptive server (PicoServer) that can be configure
         'totalCount': 1,
         'sdkLibraryHits': [],
         'packageHits': [
-          {'package': 'async', 'score': closeTo(0.24, 0.01)},
+          {'package': 'async', 'score': closeTo(0.26, 0.01)},
         ],
       });
     });
@@ -335,7 +335,7 @@ server.dart adds a small, prescriptive server (PicoServer) that can be configure
         'sdkLibraryHits': [],
         'packageHits': [
           {'package': 'http', 'score': closeTo(0.92, 0.01)},
-          {'package': 'async', 'score': closeTo(0.41, 0.01)},
+          {'package': 'async', 'score': closeTo(0.52, 0.01)},
         ],
       });
 
@@ -422,7 +422,7 @@ server.dart adds a small, prescriptive server (PicoServer) that can be configure
         'totalCount': 1,
         'sdkLibraryHits': [],
         'packageHits': [
-          {'package': 'async', 'score': closeTo(0.41, 0.01)},
+          {'package': 'async', 'score': closeTo(0.52, 0.01)},
         ],
       });