[GLE-8861] address comments;

Author: jue-yuan

gds/vector/cosine_distance.gsql

@@ -28,6 +28,8 @@ CREATE FUNCTION gds.vector.cosine_distance(list<double> list1, list<double> list
   Exceptions:
       list_size_mismatch (90000):
           Raised when the input lists are not of equal size.
+      zero_divisor(90001);
+          Raised either list is all zero to avoid zero-divisor issue.
 
   Logic Overview:
       Validates that both input vectors have the same length.
@@ -42,15 +44,24 @@ CREATE FUNCTION gds.vector.cosine_distance(list<double> list1, list<double> list
   */
 
   EXCEPTION list_size_mismatch (90000);
+  EXCEPTION zero_divisor(90001);
   ListAccum<double> @@myList1 = list1;
   ListAccum<double> @@myList2 = list2;
 
   IF (@@myList1.size() != @@myList2.size()) THEN
     RAISE list_size_mismatch ("Two lists provided for gds.vector.cosine_distance have different sizes.");
   END;
 
-  double innerP = inner_product(@@myList1, @@myList2);
+  double inner_p = inner_product(@@myList1, @@myList2);
   double v1_magn = sqrt(inner_product(@@myList1, @@myList1));
   double v2_magn = sqrt(inner_product(@@myList2, @@myList2));
+  IF (abs(v1_magn) < 0.0000001) THEN
+    // use a small positive float to avoid numeric comparison error
+    RAISE zero_divisor ("The elements in the first list are all zero. It will introduce a zero divisor.");
+  END;
+  IF (abs(v1_magn) < 0.0000001) THEN
+    // use a small positive float to avoid numeric comparison error
+    RAISE zero_divisor ("The elements in the second list are all zero. It will introduce a zero divisor.");
+  END;
   RETURN (1 - innerP / (v1_magn * v2_magn));
 }

gds/vector/distance.gsql

@@ -32,7 +32,9 @@ CREATE FUNCTION gds.vector.distance(list<double> list1, list<double> list2, stri
   Exceptions:
       list_size_mismatch (90000):
           Raised when the input vectors are not of equal size.
-      invalid_metric_type (90001):
+      zero_divisor(90001);
+          Raised either list is all zero to avoid zero-divisor issue.
+      invalid_metric_type (90002):
           Raised when an unsupported distance metric is provided.
 
   Logic Overview:
@@ -55,7 +57,8 @@ CREATE FUNCTION gds.vector.distance(list<double> list1, list<double> list2, stri
   */
 
   EXCEPTION list_size_mismatch (90000);
-  EXCEPTION invalid_metric_type (90001);
+  EXCEPTION zero_divisor(90001);
+  EXCEPTION invalid_metric_type (90002);
   ListAccum<double> @@myList1 = list1;
   ListAccum<double> @@myList2 = list2;
 
@@ -68,7 +71,18 @@ CREATE FUNCTION gds.vector.distance(list<double> list1, list<double> list2, stri
 
   CASE lower(metric)
     WHEN "cosine" THEN
-      @@myResult = 1 - inner_product(@@myList1, @@myList2) / (sqrt(inner_product(@@myList1, @@myList1)) * sqrt(inner_product(@@myList2, @@myList2)));
+      double inner_p = inner_product(@@myList1, @@myList2);
+      double v1_magn = sqrt(inner_product(@@myList1, @@myList1));
+      double v2_magn = sqrt(inner_product(@@myList2, @@myList2));
+      IF (abs(v1_magn) < 0.0000001) THEN
+      // use a small positive float to avoid numeric comparison error
+        RAISE zero_divisor ("The elements in the first list are all zero. It will introduce a zero divisor.");
+      END;
+      IF (abs(v2_magn) < 0.0000001) THEN
+      // use a small positive float to avoid numeric comparison error
+        RAISE zero_divisor ("The elements in the second list are all zero. It will introduce a zero divisor.");
+      END;
+      @@myResult = 1 - inner_p / (v1_magn * v2_magn);
     WHEN "l2" THEN
       FOREACH i IN RANGE [0, @@myList1.size() - 1 ] DO
         @@sqrSum += (@@myList1.get(i) - @@myList2.get(i)) * (@@myList1.get(i) - @@myList2.get(i));

gds/vector/norm.gsql

@@ -53,23 +53,16 @@ CREATE FUNCTION gds.vector.norm(list<double> list1, string metric) RETURNS(float
 
   EXCEPTION invalid_metric_type (90001);
   ListAccum<double> @@myList1 = list1;
-  ListAccum<double> @@myList2;
-
-  FOREACH i IN RANGE [0, @@myList1.size() - 1] DO
-    @@myList2 += 0;
-  end;
 
   SumAccum<float> @@myResult;
   SumAccum<float> @@sqrSum;
 
   CASE lower(metric)
     WHEN "l2" THEN
-      FOREACH i IN RANGE [0, @@myList1.size() - 1 ] DO
-        @@sqrSum += (@@myList1.get(i) - @@myList2.get(i)) * (@@myList1.get(i) - @@myList2.get(i));
-      END;
-      @@myResult = sqrt(@@sqrSum);
+      @@myResult = sqrt(inner_product(@@myList1, @@myList1));
     WHEN "ip" THEN
-      @@myResult = inner_product(@@myList1, @@myList2);
+      // the result of inner product between any vector and all-zero vector should always be 0
+      @@myResult = 0;
     ELSE
       RAISE invalid_metric_type ("Invalid metric algorithm provided, currently supported: l2 and ip.");
     END