That's not quite what I'm looking for.  Let me provide an example. =  I have a rowmatrix A that is nxm and I have two local matrices b and = c.  b is mx1 and c is nx1.  In my spark job I wish to perform the= following two computations

A*b

and

A^T*c

I don't think this is possible without being able to transpose a rowmatr= ix.  Am I correct?

Thanks,

Alex

Sent: Monday, January 12, 2015 1:58 PM
To: Alex Minnaar
Cc: user@spark.incubator.apache.org
Subject: Re: RowMatrix multiplication

As you mentioned, you can perform A * b, where A is a rowm= atrix and b is a local matrix.

From your email, I figure you want to compute b * A^T. To do this, you= can compute C =3D A b^T, whose result is the transpose of what you were lo= oking for, i.e. C^T =3D b * A^T. To undo the transpose, you would have tran= spose C manually yourself. Be careful though, because the result might not have each Row fit in memory on a sing= le machine, which is what RowMatrix requires. This danger is why we didn't = provide a transpose operation in RowMatrix natively.

To address this and more, there is an effort to provide more comprehen= sive linear algebra through block matrices, which will likely make it to 1.= 3:

Best,
Reza

On Mon, Jan 12, 2015 at 6:33 AM, Alex Minnaar <aminnaa= r@verticalscope.com> wrote:

I have a rowMatrix on which I want to perform two multiplications. = The first is a right multiplication with a local matrix which is fine.&nbs= p; But after that I also wish to right multiply the transpose of = my rowMatrix with a different local matrix.  I understand that there is no functionality to transpose a rowMatrix at this time but I= was wondering if anyone could suggest a any kind of work-around for this.&= nbsp; I had thought that I might be able to initially create two rowMatrice= s - a normal version and a transposed version - and use either when appropriate.  Can anyone think of anoth= er alternative?

Thanks,

Alex

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