Re: [eigen] Can I force (or hint) Eigen to not vectorise a particular expression?

[Gael Guennebaud <gael.guennebaud@xxxxxxxxx>]

On Mon, Apr 21, 2014 at 6:10 PM, Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:

* If you have a limited range of block-sizes (known at compile-time),
  you may consider implementing it using a virtual class with
  specializations for each occurring block size.  You'll need some kind
  of non-virtual intermediate class, which will introduce additional
  overhead, so overall it might not be worth the effort.

A much lesser painful trick is to use A.lazyProduct(B) instead of A*B and keep vectorization ON. Of course this will be a little bit less efficient than fixed-size specialization, but that should be enough to see a nice speedup with 2s change.

gael.