Update closeness (rawscore) and distance for the dotproduct distance metric.

closeness and rawScore rank features return the dot product.
distance rank feature returns the negative dot product.

4 files changed, 24 insertions, 22 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 9d0b7259912..363193da110 100644
--- a/searchlib/src/tests/tensor/distance_functions/distance_functions_test.cpp
+++ b/searchlib/src/tests/tensor/distance_functions/distance_functions_test.cpp
@@ -528,8 +528,10 @@ double computeTransformedMipsChecked(TypedCells a, TypedCells b, bool check_inse
     double closeness_r = d_r->to_rawscore(result);
     EXPECT_DOUBLE_EQ(closeness_n, closeness_f);
     EXPECT_DOUBLE_EQ(closeness_n, closeness_r);
-    EXPECT_GT(closeness_n, 0.0);
-    EXPECT_LE(closeness_n, 1.0);
+    EXPECT_DOUBLE_EQ(closeness_n, -result);
+    EXPECT_DOUBLE_EQ(result, d_n->to_distance(closeness_n));
+    EXPECT_DOUBLE_EQ(result, d_f->to_distance(closeness_f));
+    EXPECT_DOUBLE_EQ(result, d_r->to_distance(closeness_r));
     if (check_insert) {
         auto d_i = dbl_dff.for_insertion_vector(a);
         EXPECT_DOUBLE_EQ(d_i->calc(b), result);
@@ -601,11 +603,6 @@ TEST(DistanceFunctionsTest, transformed_mips_growing_norm)
     EXPECT_DOUBLE_EQ(4.0, f->calc(t(p7)));
     EXPECT_DOUBLE_EQ(-4.0, f->calc(t(p8)));
 
-    // closeness
-    EXPECT_DOUBLE_EQ(0.25, f->to_rawscore(1.0));
-    EXPECT_DOUBLE_EQ(0.50, f->to_rawscore(0.0));
-    EXPECT_DOUBLE_EQ(0.75, f->to_rawscore(-1.0));
-
     // now "insert" a bigger vector
     f = dff.for_insertion_vector(t(p6));
     EXPECT_DOUBLE_EQ(0.0, f->calc(t(p1)));
@@ -618,12 +615,6 @@ TEST(DistanceFunctionsTest, transformed_mips_growing_norm)
     // now max squared norm is 32, so p1 is "closer" to itself
     f = dff.for_insertion_vector(t(p1));
     EXPECT_DOUBLE_EQ(-32.0, f->calc(t(p1)));
-    // closeness (rawscore) is also different:
-    EXPECT_DOUBLE_EQ(0.25, f->to_rawscore(32.0));
-    EXPECT_DOUBLE_EQ(1/3., f->to_rawscore(16.0));
-    EXPECT_DOUBLE_EQ(0.50, f->to_rawscore(0.0));
-    EXPECT_DOUBLE_EQ(2/3., f->to_rawscore(-16.0));
-    EXPECT_DOUBLE_EQ(0.75, f->to_rawscore(-32.0));
 
     // also closer to other small vectors
     EXPECT_DOUBLE_EQ(-31.0, f->calc(t(p2)));
diff --git a/searchlib/src/vespa/searchlib/features/distancefeature.cpp b/searchlib/src/vespa/searchlib/features/distancefeature.cpp
index f601c91a0b2..4f98625d0e1 100644
--- a/searchlib/src/vespa/searchlib/features/distancefeature.cpp
+++ b/searchlib/src/vespa/searchlib/features/distancefeature.cpp
@@ -58,11 +58,11 @@ ConvertRawscoreToDistance::execute(uint32_t docId)
         const TermFieldMatchData *tfmd = _md->resolveTermField(elem.handle);
         if (tfmd->getDocId() == docId) {
             feature_t invdist = tfmd->getRawScore();
-            feature_t converted = (1.0 / invdist) - 1.0;
+            feature_t converted = elem.calc ? elem.calc->function().to_distance(invdist) : ((1.0 / invdist) - 1.0);
             min_distance = std::min(min_distance, converted);
         } else if (elem.calc) {
             feature_t invdist = elem.calc->calc_raw_score(docId);
-            feature_t converted = (1.0 / invdist) - 1.0;
+            feature_t converted = elem.calc->function().to_distance(invdist);
             min_distance = std::min(min_distance, converted);
         }
     }
diff --git a/searchlib/src/vespa/searchlib/tensor/distance_function.h b/searchlib/src/vespa/searchlib/tensor/distance_function.h
index 31a837d17f4..a06c451d5e2 100644
--- a/searchlib/src/vespa/searchlib/tensor/distance_function.h
+++ b/searchlib/src/vespa/searchlib/tensor/distance_function.h
@@ -13,11 +13,23 @@ class DistanceConverter {
 public:
     virtual ~DistanceConverter() = default;
 
-    // convert threshold (external distance units) to internal units
+    /**
+     * Convert threshold (external distance units) to internal units.
+     */
     virtual double convert_threshold(double threshold) const = 0;
 
-    // convert internal distance to rawscore (1.0 / (1.0 + d))
+    /**
+     * Convert internal distance to rawscore (also used as closeness).
+     */
     virtual double to_rawscore(double distance) const = 0;
+
+    /**
+     * Convert rawscore to external distance.
+     * Override this when the rawscore is NOT defined as (1.0 / (1.0 + external_distance)).
+     */
+    virtual double to_distance(double rawscore) const {
+        return (1.0 / rawscore) - 1.0;
+    }
 };
 
 }
diff --git a/searchlib/src/vespa/searchlib/tensor/mips_distance_transform.cpp b/searchlib/src/vespa/searchlib/tensor/mips_distance_transform.cpp
index 1e238aaacc7..16f9eeeabc2 100644
--- a/searchlib/src/vespa/searchlib/tensor/mips_distance_transform.cpp
+++ b/searchlib/src/vespa/searchlib/tensor/mips_distance_transform.cpp
@@ -62,11 +62,10 @@ public:
         return threshold;
     }
     double to_rawscore(double distance) const override {
-        double dp = -distance;
-        double t1 = dp / _max_sq_norm;
-        double t2 = t1 / (1.0 + std::fabs(t1));
-        double r = (t2 + 1.0) * 0.5;
-        return r;
+        return -distance;
+    }
+    double to_distance(double rawscore) const override {
+        return -rawscore;
     }
     double calc_with_limit(const vespalib::eval::TypedCells& rhs, double) const override {
         return calc(rhs);