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

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*To*: eigen <eigen@xxxxxxxxxxxxxxxxxxx>*Subject*: Re: [eigen] Can I force (or hint) Eigen to not vectorise a particular expression?*From*: Gael Guennebaud <gael.guennebaud@xxxxxxxxx>*Date*: Tue, 22 Apr 2014 10:36:13 +0200*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type; bh=3qTQhK+raKjE2c5+74oyN4GM2ETjMBTcKTb/+7L0t+k=; b=eURVjwDtmZLpkdBkpUsZie5MewcIhqsczVFNUJug9dOmpnE5Bctj4qTYhHRKmFZ+mj Elstk1XCxnS1MSXiQccwz8d/dI0N7AXgLu9mGixDBY92JP8hOcdrkXg1Dt33n8/I9hmb /Qt1z7QzxTPzfPrTNuvyJqqG5Lv3IoXR8uYEWwD9lC8RDunikALgYNHeV6cIT5eiGxeN Xgp4NGhONS/lddAe2PZ8KWQthA9NemL0dEn+4T4Rd3DZw4WBfZwgbbiaBck8/Z9RrfLS SvypmgavoGowXUNCOPnYq6QCLk9hIJZYTBMRKsnxhs/nkx5xozbJyUH9//BLXlnAX/DP smFA==

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.

**References**:**[eigen] Can I force (or hint) Eigen to not vectorise a particular expression?***From:*Daniel.Vollmer

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

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