zhengruifeng commented on a change in pull request #26550:
[WIP][SPARK-29334][ML][MLLIB] Support for basic vector operators
URL: https://github.com/apache/spark/pull/26550#discussion_r353057261
##########
File path: mllib-local/src/main/scala/org/apache/spark/ml/linalg/Vectors.scala
##########
@@ -753,6 +799,24 @@ class SparseVector @Since("2.0.0") (
}.unzip
new SparseVector(selectedIndices.length, sliceInds.toArray,
sliceVals.toArray)
}
+
+ def +(v: Vector): Vector = {
+ require(this.size == v.size)
+ v match {
+ case dv: DenseVector =>
+ val arr = dv.values.clone
+ for (i <- this.indices) arr(i) += this(i)
+ Vectors.dense(arr)
+ case sv: SparseVector =>
Review comment:
Current impl: 1, needs distinct and sort, 2, complexity = O(nnz * log(nnz))
It maybe faster to add two `SparseVector` in this way:
```scala
def add(v: SparseVector): SparseVector = {
require(size == v.size)
if (v.indices.isEmpty) {
copy
} else if (indices.isEmpty) {
v.copy
} else {
val thisIndices = indices
val thatIndices = v.indices
val thisValues = values
val thatValues = v.values
val indicesBuilder = mutable.ArrayBuilder.make[Int]
val valuesBuilder = mutable.ArrayBuilder.make[Double]
var thisCur = 0
var thatCur = 0
while (thisCur < thisIndices.length && thatCur < thatIndices.length) {
val thisIndex = thisIndices(thisCur)
val thatIndex = thatIndices(thatCur)
val (index, value) = if (thisIndex == thatIndex) {
val sum = thisValues(thisCur) + thatValues(thatCur)
thisCur += 1
thatCur += 1
(thisIndex, sum)
} else if (thisIndex < thatIndex) {
val sum = thisValues(thisCur)
thisCur += 1
(thisIndex, sum)
} else {
val sum = thatValues(thatCur)
thatCur += 1
(thatIndex, sum)
}
if (value != 0.0) {
indicesBuilder += index
valuesBuilder += value
}
}
if (thisCur < thisIndices.length) {
while (thisCur < thisIndices.length) {
val index = thisIndices(thisCur)
val value = thisValues(thisCur)
if (value != 0.0) {
indicesBuilder += index
valuesBuilder += value
}
thisCur += 1
}
} else if (thatCur < thatIndices.length) {
while (thatCur < thatIndices.length) {
val index = thatIndices(thatCur)
val value = thatValues(thatCur)
if (value != 0.0) {
indicesBuilder += index
valuesBuilder += value
}
thatCur += 1
}
}
new SparseVector(size, indicesBuilder.result(), valuesBuilder.result())
}
}
```
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