[eigen] Block CG(p=1) vs CG Classic

[Pedro Torres <torres.pedrozpk@xxxxxxxxx>]

Dear EIGEN Team and Users,

I'm new here and I have a newbie question. I have implemented a version of Block Conjugate Gradient, to resolve AX=B where A(nxn), X(nxp) and B(nxp).. Then, I compare the walltime of this block version (using p=1) agains Classics CG using just VectorXd. Result: the block version took more time.

Specifically I see that the operation A*V, with V defined as MatrixXd V(n,1) took more time than the operations A*v, with  v defined as VectorXd v(n). Is this an expected result?. Can I do something to get approximately more closer results?.

I attached some snapshot from VTune comparing this runs.

Thanks in advance.

Best Regards

Pedro Torres

Block CG

CG Classic

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Pedro Torres