Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/8565#discussion_r38515156
--- Diff: mllib/src/main/scala/org/apache/spark/mllib/linalg/Matrices.scala
---
@@ -278,7 +278,8 @@ class DenseMatrix @Since("1.3.0") (
}
override def hashCode: Int = {
- com.google.common.base.Objects.hashCode(numRows : Integer, numCols:
Integer, toArray)
+ val state = Seq(numRows, numCols, Arrays.hashCode(values),
isTransposed.hashCode)
--- End diff --
Crazy, you might ask on the breeze list if you have time, to make sure
we're not missing something, but that seems like a valid test.
We can avoid using either Breeze method in these implementations in order
to write a version that we know is consistent and correct. On the other hand,
it's likely that `==` is correct, and it's just that hash code isn't
implemented. I suppose it should be possible to write a hash code that must be
consistent with the plain meaning of equality for matrices, by making it a
function of all (non-zero) elements and their positions or something. That is,
is your `hashCode` going to be consistent with Breeze `==`? that's the
important thing to guarantee.
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