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[Spark-7422][MLLIB] Add argmax to Vector, SparseVector #6112

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[Spark-7422][MLLIB] Add argmax to Vector, SparseVector #6112

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04677af
initial work on adding argmax to Vector and SparseVector
May 11, 2015
3cffed4
Adding unit tests for argmax functions for Dense and Sparse vectors
May 12, 2015
df9538a
Added argmax to sparse vector and added unit test
May 12, 2015
4526acc
Merge branch 'master' of github.com:apache/spark into SPARK-7422
May 13, 2015
eeda560
Fixing SparseVector argmax function to ignore zero values while doing…
May 15, 2015
af17981
Initial work fixing bug that was made clear in pr
dittmarg May 22, 2015
f21dcce
commit
GeorgeDittmar May 25, 2015
b1f059f
Added comment before we start arg max calculation. Updated unit tests…
GeorgeDittmar May 29, 2015
3ee8711
Fixing corner case issue with zeros in the active values of the spars…
GeorgeDittmar Jun 1, 2015
ee1a85a
Cleaning up unit tests a bit and modifying a few cases
GeorgeDittmar Jun 1, 2015
d5b5423
Fixing code style and updating if logic on when to check for zero values
GeorgeDittmar Jun 9, 2015
ac53c55
changing dense vector argmax unit test to be one line call vs 2
GeorgeDittmar Jun 9, 2015
aa330e3
Fixing some last if else spacing issues
GeorgeDittmar Jun 9, 2015
f2eba2f
Cleaning up unit tests to be fewer lines
GeorgeDittmar Jun 9, 2015
b22af46
Fixing spaces between commas in unit test
GeorgeDittmar Jun 10, 2015
42341fb
refactoring arg max check to better handle zero values
GeorgeDittmar Jul 9, 2015
5fd9380
fixing style check error
GeorgeDittmar Jul 9, 2015
98058f4
Merge branch 'master' of github.com:apache/spark into SPARK-7422
GeorgeDittmar Jul 15, 2015
2ea6a55
Added MimaExcludes for Vectors.argmax
GeorgeDittmar Jul 15, 2015
127dec5
update argmax impl
mengxr Jul 17, 2015
3e0a939
Merge pull request #1 from mengxr/SPARK-7422
GeorgeDittmar Jul 18, 2015
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29 changes: 24 additions & 5 deletions mllib/src/main/scala/org/apache/spark/mllib/linalg/Vectors.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -150,6 +150,12 @@ sealed trait Vector extends Serializable {
toDense
}
}

/**
* Find the index of a maximal element. Returns the first maximal element in case of a tie.
* Returns -1 if vector has length 0.
*/
def argmax: Int
}

/**
Expand Down Expand Up @@ -588,11 +594,7 @@ class DenseVector(val values: Array[Double]) extends Vector {
new SparseVector(size, ii, vv)
}

/**
* Find the index of a maximal element. Returns the first maximal element in case of a tie.
* Returns -1 if vector has length 0.
*/
private[spark] def argmax: Int = {
def argmax: Int = {
if (size == 0) {
-1
} else {
Expand Down Expand Up @@ -717,6 +719,23 @@ class SparseVector(
new SparseVector(size, ii, vv)
}
}

override def argmax: Int = {
if (size == 0) {
-1
} else {
var maxIdx = indices(0)
var maxValue = values(0)

foreachActive { (i, v) =>
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@mengxr mengxr May 14, 2015

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This is not correct if all nonzeros are negative and there exist inactive (zero) entries.

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@GeorgeDittmar GeorgeDittmar May 14, 2015

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"there exist inactive (zero) entries" are you meaning we have values in the sparse vector that are zero but are set to not active? I thought that the sparse vector had you define what indices have active elements and that indices.size must equal the size of the values in that vector so I am not sure how you get into the state I think you are describing. Do you have an example?

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@GeorgeDittmar GeorgeDittmar May 15, 2015

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Wait are you getting at say I have a sparse vector with zero in it and an assigned index? Like indices = (1,2,3) values = (-1,0,-.5)? If thats the case then yes I now see what you are saying.

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@mengxr mengxr May 20, 2015

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The bug still exists. Take a sparse vector val sv = SparseVector(5, Array(1, 3), Array(-1, -5)) for example, sv.argmax should return one from {0, 2, 4} because 0 is the max value in this vector.

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@GeorgeDittmar GeorgeDittmar May 21, 2015

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I added unit tests to cover this and they appear to be passing so maybe I am totally misunderstanding the bug you are discussing? Or more likely I am misunderstanding the usage of the sparse vector implementation in regards to the inactive vs active elements?

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@mengxr mengxr May 22, 2015

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Sorry, I didn't explain this clearly. All inactive values in a sparse vector are zeros. The edge case here is that zero could be the max value of the entries. For example, [-1.0, 0.0, -3.0].argmax == 1 but 0.0 doesn't appear in foreachActive if the sparse vector is SparseVector(3, Array(0, 2), Array(-1.0, -3.0)). If we only look at the active values, the argmax would be 0 as -1.0 is the max among active values. So we need to cover the following cases if all active values are negative:

  1. if the number of active entries are the same as vector size (i.e., no inactive entries), use the current max and its index,
  2. if there are inactive entries, find one and output its index.

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@GeorgeDittmar GeorgeDittmar May 22, 2015

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Ok yeah it sounds like I misunderstood the inactive vs active node concept. I'll get a fix in for that. I was assuming inactive meant we wanted to just ignore it and do the argmax over the active portions.

if(v > maxValue){
maxIdx = i
maxValue = v
}
}
maxIdx
}
}
}

object SparseVector {
Expand Down
24 changes: 24 additions & 0 deletions mllib/src/test/scala/org/apache/spark/mllib/linalg/VectorsSuite.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -63,11 +63,35 @@ class VectorsSuite extends FunSuite {
assert(vec.toArray.eq(arr))
}

test("dense argmax"){
val vec = Vectors.dense(Array.empty[Double]).asInstanceOf[DenseVector]
val noMax = vec.argmax
assert(noMax === -1)
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@MechCoder MechCoder Jun 8, 2015

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nitpick: I think this can be combined into a single line, here and elsewhere

assert(vec.max === -1)


val vec2 = Vectors.dense(arr).asInstanceOf[DenseVector]
val max = vec2.argmax
assert(max === 3)
}

test("sparse to array") {
val vec = Vectors.sparse(n, indices, values).asInstanceOf[SparseVector]
assert(vec.toArray === arr)
}

test("sparse argmax"){
val vec = Vectors.sparse(0,Array.empty[Int],Array.empty[Double]).asInstanceOf[SparseVector]
val noMax = vec.argmax
assert(noMax === -1)

val vec2 = Vectors.sparse(n,indices,values).asInstanceOf[SparseVector]
val max = vec2.argmax
assert(max === 3)

val vec3 = Vectors.sparse(5,Array(1,3,4),Array(1.0,.5,.7))
val max2 = vec3.argmax
assert(max2 === 1)
}

test("vector equals") {
val dv1 = Vectors.dense(arr.clone())
val dv2 = Vectors.dense(arr.clone())
Expand Down