About packed storage matrix multiplication

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About packed storage matrix multiplication

Postby chxyike » Thu Nov 11, 2010 2:47 am

Hello all,

I would like to ask, if there is any subroutine to compute such as CP = AP * BP, where all three matrices are in packed storage. If there is no such subroutine, whether there is such C = AP * B, where AP is in packed storage, B and C are general matrices.

I know there is a subroutine named DPPSV, but it can only be used for solving AP * X = B to obtain the X matrix.

Best regards to you all,
Weiyong ( chxyike@gmail.com )
chxyike
 
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Re: About packed storage matrix multiplication

Postby Julien Langou » Thu Nov 11, 2010 1:22 pm

Such a subroutine would be part of the BLAS but there is no such subroutine in the BLAS. ( The reason is that it is not possible to perform this operation efficiently due to the storage format of the matrix A ("AP"). )

May I advise you to have a look at xPFSV ( as opposed to xPPSV) ??

If you have your matrix store in packed format (so that you would use xPPSV) then you can first convert it to xTPTTF then call xPFSV.
You can try to store your matrix directly in PF format as well.

Then for the matrix matrix multiply, you will need to think some but you can do it with two DSYMM and two DGEMM ...

--julien.
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Re: About packed storage matrix multiplication

Postby chxyike » Fri Nov 12, 2010 8:25 am

OK, let me try. Thank you, Julien. :)
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