Added normalize_l2 function

CHANGELOG.md

@@ -3,6 +3,7 @@
 - Added HNSW index type
 - Added support for parallel index builds
 - Added `l1_distance` function
+- Added `normalize_l2` function
 - Added element-wise multiplication for vectors
 - Added `sum` aggregate
 - Improved performance of distance functions

README.md

@@ -392,6 +392,7 @@ cosine_distance(vector, vector) → double precision | cosine distance
 inner_product(vector, vector) → double precision | inner product
 l2_distance(vector, vector) → double precision | Euclidean distance
 l1_distance(vector, vector) → double precision | taxicab distance [unreleased]
+normalize_l2(vector) → vector | normalize with Euclidean norm [unreleased]
 vector_dims(vector) → integer | number of dimensions
 vector_norm(vector) → double precision | Euclidean norm
 

sql/vector--0.4.4--0.5.0.sql

@@ -4,6 +4,9 @@
 CREATE FUNCTION l1_distance(vector, vector) RETURNS float8
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
+CREATE FUNCTION normalize_l2(vector) RETURNS vector
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
 CREATE FUNCTION vector_mul(vector, vector) RETURNS vector
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 

sql/vector.sql

@@ -49,6 +49,9 @@ CREATE FUNCTION vector_dims(vector) RETURNS integer
 CREATE FUNCTION vector_norm(vector) RETURNS float8
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
+CREATE FUNCTION normalize_l2(vector) RETURNS vector
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
 CREATE FUNCTION vector_add(vector, vector) RETURNS vector
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 

src/vector.c

@@ -745,6 +745,45 @@ vector_norm(PG_FUNCTION_ARGS)
 	PG_RETURN_FLOAT8(sqrt((double) norm));
 }
 
+/*
+ * Normalize a vector with the L2 norm
+ */
+PGDLLEXPORT PG_FUNCTION_INFO_V1(normalize_l2);
+Datum
+normalize_l2(PG_FUNCTION_ARGS)
+{
+	Vector	   *a = PG_GETARG_VECTOR_P(0);
+	float	   *ax = a->x;
+	float		norm = 0.0;
+	Vector	   *result;
+	float	   *rx;
+
+	result = InitVector(a->dim);
+	rx = result->x;
+
+	/* Auto-vectorized */
+	for (int i = 0; i < a->dim; i++)
+		norm += ax[i] * ax[i];
+
+	norm = sqrtf(norm);
+
+	if (norm > 0)
+	{
+		/* Auto-vectorized */
+		for (int i = 0, imax = a->dim; i < imax; i++)
+			rx[i] = ax[i] / norm;
+
+		/* Check for overflow */
+		for (int i = 0, imax = a->dim; i < imax; i++)
+		{
+			if (isinf(rx[i]))
+				float_overflow_error();
+		}
+	}
+
+	PG_RETURN_POINTER(result);
+}
+
 /*
  * Add vectors
  */

test/expected/functions.out

@@ -48,6 +48,30 @@ SELECT vector_norm('[0,1]');
            1
 (1 row)
 
+SELECT normalize_l2('[3,4]');
+ normalize_l2 
+--------------
+ [0.6,0.8]
+(1 row)
+
+SELECT normalize_l2('[3,0]');
+ normalize_l2 
+--------------
+ [1,0]
+(1 row)
+
+SELECT normalize_l2('[0,0.1]');
+ normalize_l2 
+--------------
+ [0,1]
+(1 row)
+
+SELECT normalize_l2('[0,0]');
+ normalize_l2 
+--------------
+ [0,0]
+(1 row)
+
 SELECT l2_distance('[0,0]', '[3,4]');
  l2_distance 
 -------------

test/sql/functions.sql

@@ -12,6 +12,11 @@ SELECT round(vector_norm('[1,1]')::numeric, 5);
 SELECT vector_norm('[3,4]');
 SELECT vector_norm('[0,1]');
 
+SELECT normalize_l2('[3,4]');
+SELECT normalize_l2('[3,0]');
+SELECT normalize_l2('[0,0.1]');
+SELECT normalize_l2('[0,0]');
+
 SELECT l2_distance('[0,0]', '[3,4]');
 SELECT l2_distance('[0,0]', '[0,1]');
 SELECT l2_distance('[1,2]', '[3]');