[SPARK-29121][ML][MLLIB] Support for dot product operation on Vector(s)

mllib-local/src/main/scala/org/apache/spark/ml/linalg/Vectors.scala

@@ -178,6 +178,13 @@ sealed trait Vector extends Serializable {
    */
   @Since("2.0.0")
   def argmax: Int
+
+  /**
+   * Calculate the dot product of this vector with another.
+   *
+   * If `size` does not match an [IllegalArgumentException] is thrown.
+   */
+  def dot(v: Vector): Double = BLAS.dot(this, v)
 }
 
 /**
@@ -239,6 +246,13 @@ object Vectors {
     }.toSeq)
   }
 
+  /**
+   * Calculate the dot product of two vectors.
+   *
+   * If `size` does not match an [IllegalArgumentException] is thrown.
+   */
+  def dot(v1: Vector, v2: Vector): Double = BLAS.dot(v1, v2)
+
   /**
    * Creates a vector of all zeros.
    *

mllib-local/src/test/scala/org/apache/spark/ml/linalg/VectorsSuite.scala

@@ -380,4 +380,29 @@ class VectorsSuite extends SparkMLFunSuite {
       Vectors.sparse(-1, Array((1, 2.0)))
     }
   }
+
+  test("dot product only supports vectors of same size") {
+    intercept[IllegalArgumentException]{ Vectors.dot(Vectors.dense(arr), Vectors.zeros(1)) }
+  }
+
+  test("dense vector dot product") {
+    val dv = Vectors.dense(arr)
+    assert(Vectors.dot(dv, dv) === 0.26)
+    assert(dv.dot(dv) === 0.26)
+  }
+
+  test("sparse vector dot product") {
+    val sv = Vectors.sparse(n, indices, values)
+    assert(Vectors.dot(sv, sv) === 0.26)
+    assert(sv.dot(sv) === 0.26)
+  }
+
+  test("mixed sparse and dense vector dot product") {
+    val sv = Vectors.sparse(n, indices, values)
+    val dv = Vectors.dense(arr)
+    assert(Vectors.dot(sv, dv) === 0.26)
+    assert(Vectors.dot(dv, sv) === 0.26)
+    assert(sv.dot(dv) === 0.26)
+    assert(dv.dot(sv) === 0.26)
+  }
 }

mllib/src/main/scala/org/apache/spark/mllib/linalg/Vectors.scala

@@ -204,6 +204,13 @@ sealed trait Vector extends Serializable {
    */
   @Since("2.0.0")
   def asML: newlinalg.Vector
+
+  /**
+   * Calculate the dot product of this vector with another.
+   *
+   * If `size` does not match an [IllegalArgumentException] is thrown.
+   */
+  def dot(v: Vector): Double = BLAS.dot(this, v)
 }
 
 /**
@@ -351,6 +358,13 @@ object Vectors {
     }.toSeq)
   }
 
+  /**
+   * Calculate the dot product of two vectors.
+   *
+   * If `size` does not match an [IllegalArgumentException] is thrown.
+   */
+  def dot(v1: Vector, v2: Vector): Double = BLAS.dot(v1, v2)
+
   /**
    * Creates a vector of all zeros.
    *

mllib/src/test/scala/org/apache/spark/mllib/linalg/VectorsSuite.scala

@@ -510,4 +510,29 @@ class VectorsSuite extends SparkFunSuite with Logging {
       Vectors.sparse(-1, Array((1, 2.0)))
     }
   }
+
+  test("dot product only supports vectors of same size") {
+    intercept[IllegalArgumentException]{ Vectors.dot(Vectors.dense(arr), Vectors.zeros(1)) }
+  }
+
+  test("dense vector dot product") {
+    val dv = Vectors.dense(arr)
+    assert(Vectors.dot(dv, dv) === 0.26)
+    assert(dv.dot(dv) === 0.26)
+  }
+
+  test("sparse vector dot product") {
+    val sv = Vectors.sparse(n, indices, values)
+    assert(Vectors.dot(sv, sv) === 0.26)
+    assert(sv.dot(sv) === 0.26)
+  }
+
+  test("mixed sparse and dense vector dot product") {
+    val sv = Vectors.sparse(n, indices, values)
+    val dv = Vectors.dense(arr)
+    assert(Vectors.dot(sv, dv) === 0.26)
+    assert(Vectors.dot(dv, sv) === 0.26)
+    assert(sv.dot(dv) === 0.26)
+    assert(dv.dot(sv) === 0.26)
+  }
 }