Github user dbtsai commented on a diff in the pull request:
https://github.com/apache/spark/pull/3462#discussion_r20967444
--- Diff: mllib/src/main/scala/org/apache/spark/mllib/linalg/Vectors.scala
---
@@ -261,6 +261,57 @@ object Vectors {
sys.error("Unsupported Breeze vector type: " + v.getClass.getName)
}
}
+
+ /**
+ * Returns the p-norm of this vector.
+ * @param vector input vector.
+ * @param p norm.
+ * @return norm in L^p^ space.
+ */
+ private[spark] def norm(vector: Vector, p: Double): Double = {
+ require(p >= 1.0)
+ val values = vector match {
+ case dv: DenseVector => dv.values
+ case sv: SparseVector => sv.values
+ case v => throw new IllegalArgumentException("Do not support vector
type " + v.getClass)
+ }
+ val size = values.size
+
+ if (p == 1) {
+ var sum = 0.0
+ var i = 0
+ while (i < size) {
+ sum += math.abs(values(i))
+ i += 1
+ }
+ sum
+ } else if (p == 2) {
+ var sum = 0.0
+ var i = 0
+ while (i < size) {
+ sum += values(i) * values(i)
--- End diff --
@mengxr Having `var value` outside will generate the same bytecode. It
doesn't make sense, since in the bytecode, it just stores the value to stack,
and no difference between two version.
@srowen I'm very curious about this myself. :P I'm using ASM Bytecode
Outline plugin in intellij, https://plugins.jetbrains.com/plugin/5918 so I can
generate the bytecode by just simple right click. We use it to find couple
boxing/unboxing performance issue at Alpine, and it's very useful.
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