add unit test for Hamming distance metric

1 files changed, 40 insertions, 0 deletions

diff --git a/searchlib/src/tests/tensor/distance_functions/distance_functions_test.cpp b/searchlib/src/tests/tensor/distance_functions/distance_functions_test.cpp
index 9d240bc688a..f11a28b8716 100644
--- a/searchlib/src/tests/tensor/distance_functions/distance_functions_test.cpp
+++ b/searchlib/src/tests/tensor/distance_functions/distance_functions_test.cpp
@@ -142,6 +142,46 @@ TEST(DistanceFunctionsTest, innerproduct_gives_expected_score)
     EXPECT_LT(i44, 0.000001);
 }
 
+TEST(DistanceFunctionsTest, hamming_gives_expected_score)
+{
+    auto ct = vespalib::eval::ValueType::CellType::DOUBLE;
+
+    auto hamming = make_distance_function(DistanceMetric::Hamming, ct);
+
+    std::vector<std::vector<double>>
+        points{{0.0, 0.0, 0.0},
+               {1.0, 0.0, 0.0},
+               {0.0, 1.0, 1.0},
+               {2.0, 2.0, 2.0},
+               {0.5, 0.5, 0.5},
+               {0.0,-1.0, 1.0},
+               {1.0, 1.0, 1.0}};
+    for (const auto & p : points) {
+        double h0 = hamming->calc(t(p), t(p));
+        EXPECT_EQ(h0, 0.0);
+        EXPECT_EQ(hamming->to_rawscore(h0), 1.0);
+    }
+    double d12 = hamming->calc(t(points[1]), t(points[2]));
+    EXPECT_EQ(d12, 3.0);
+    EXPECT_DOUBLE_EQ(hamming->to_rawscore(d12), 1.0/(1.0 + 3.0));
+
+    double d16 = hamming->calc(t(points[1]), t(points[6]));
+    EXPECT_EQ(d16, 2.0);
+    EXPECT_DOUBLE_EQ(hamming->to_rawscore(d16), 1.0/(1.0 + 2.0));
+
+    double d23 = hamming->calc(t(points[2]), t(points[3]));
+    EXPECT_EQ(d23, 3.0);
+    EXPECT_DOUBLE_EQ(hamming->to_rawscore(d23), 1.0/(1.0 + 3.0));
+
+    double d24 = hamming->calc(t(points[2]), t(points[4]));
+    EXPECT_EQ(d24, 3.0);
+    EXPECT_DOUBLE_EQ(hamming->to_rawscore(d24), 1.0/(1.0 + 3.0));
+
+    double d25 = hamming->calc(t(points[2]), t(points[5]));
+    EXPECT_EQ(d25, 1.0);
+    EXPECT_DOUBLE_EQ(hamming->to_rawscore(d25), 1.0/(1.0 + 1.0));
+}
+
 TEST(GeoDegreesTest, gives_expected_score)
 {
     auto ct = vespalib::eval::ValueType::CellType::DOUBLE;