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Bug fix of sparse vector conversion #661

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Bug fix of sparse vector conversion #661

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b85806c
Bug fix of sparse vector conversion
funes May 6, 2014
64e7198
Copy data only when necessary
funes May 6, 2014
d129a66
Add test for sparse breeze by vector builder
funes May 7, 2014
75dced3
update test case
funes May 8, 2014
edb2b9d
remove unused import
funes May 8, 2014
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6 changes: 5 additions & 1 deletion 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 @@ -136,7 +136,11 @@ object Vectors {
new DenseVector(v.toArray) // Can't use underlying array directly, so make a new one
}
case v: BSV[Double] =>
new SparseVector(v.length, v.index, v.data)
if (v.index.length == v.used) {
new SparseVector(v.length, v.index, v.data)
} else {
new SparseVector(v.length, v.index.slice(0, v.used), v.data.slice(0, v.used))
}
case v: BV[_] =>
sys.error("Unsupported Breeze vector type: " + v.getClass.getName)
}
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14 changes: 13 additions & 1 deletion mllib/src/test/scala/org/apache/spark/mllib/linalg/BreezeVectorConversionSuite.scala
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Expand Up @@ -19,7 +19,7 @@ package org.apache.spark.mllib.linalg

import org.scalatest.FunSuite

import breeze.linalg.{DenseVector => BDV, SparseVector => BSV}
import breeze.linalg.{DenseVector => BDV, SparseVector => BSV, VectorBuilder => BVB}

/**
* Test Breeze vector conversions.
Expand Down Expand Up @@ -55,4 +55,16 @@ class BreezeVectorConversionSuite extends FunSuite {
assert(vec.indices.eq(indices), "should not copy data")
assert(vec.values.eq(values), "should not copy data")
}

test("sparse breeze by vector builder to vector") {
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To ensure we can convert BSV to SparseVector correctly when there are used elements, we should use

https://github.com/scalanlp/breeze/blob/master/math/src/main/scala/breeze/linalg/SparseVector.scala#L54

with activeSize < index.length.

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@mengxr There always has activeSize < index.length in Breeze SparseVector. I don't see the problem. Do you mean we also check it in the test case?
btw, maybe we could keep a same activeSize in our SparseVector? That would avoid the data copying issue in conversion.

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The test case tests whether fromBreeze can map a BSV created by the builder correctly. But the PR handles the case when index.length > used. To test it, you should create a BSV with index.length > used and verify that fromBreeze works correctly. Try to construct a SparseArray directly and use it to construct a BSV.

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Btw, we don't carry unused data in MLlib because we need to serialize/deserialize the data.

val builder = new BVB[Double](n)
for (i <- 0 until indices.length) {
builder.add(indices(i), values(i))
}
val breeze = builder.toSparseVector
val vec = Vectors.fromBreeze(breeze).asInstanceOf[SparseVector]
assert(vec.size === n)
assert(vec.indices === indices)
assert(vec.values === values)
}
}