Cannot get outer product of a sparse vector and a dense vector

[csnardi]

Attempting to get the outer product of a sparse vector and a dense vector by themselves fails. For instance:

val a = breeze.linalg.DenseVector.zeros[Double](250)
val b = breeze.linalg.SparseVector.zeros[Double](300)
a * b.t
<console>:28: error: could not find implicit value for parameter op: breeze.linalg.operators.OpMulMatrix.Impl2[breeze.linalg.DenseVector[Double],breeze.linalg.Transpose[breeze.linalg.SparseVector[Double]],That]
       a * b.t

However, this works perfectly fine when the sparse vector is converted to a dense vector first:

res14: a * b.toDenseVector.t
breeze.linalg.DenseMatrix[Double] =
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ... (300 total)
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ...
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ...
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ...
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ...
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ...
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ...
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ...
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ...
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ...
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0  ...
0.0  0.0  0...

[bluesheeptoken]

This is probably due to the ambiguity of this operation. Would you expect to have a Dense matrix or a Sparse Matrix ?

@dlwh Any idea on that ? Would it be better to left it unimplemented ? Calculate a Sparse Matrix ? I might have some free time to implement it if there is a decision taken

[dlwh]

i think calculating a sparse matrix is a great idea. If you have cycles that would be amazing

…

On Mon, May 18, 2020 at 5:43 AM Louis FRULEUX ***@***.***> wrote: This is probably due to the ambiguity of this operation. Would you expect to have a Dense matrix or a Sparse Matrix ? @dlwh <https://github.com/dlwh> Any idea on that ? Would it be better to left it unimplemented ? Calculate a Sparse Matrix ? I might have some free time to implement it if there is a decision taken — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#779 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAACLINWGZNJLXVKJNUTLHDRSEUQRANCNFSM4MYGK2LA> .