Re: [eigen] about changeset 6eb14e380 |
[ Thread Index |
Date Index
| More lists.tuxfamily.org/eigen Archives
]
- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] about changeset 6eb14e380
- From: Gael Guennebaud <gael.guennebaud@xxxxxxxxx>
- Date: Fri, 20 Aug 2010 13:52:26 +0200
- Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:mime-version:received:in-reply-to :references:from:date:message-id:subject:to:content-type; bh=EYWnhJq6b9QbheAwfYHq8XqImMSynxb4pSThtddFPUM=; b=E55SPqFIM5AhUubIyH17puEX6iwOHRtfyJTauORwkDvrAbL3VAyN6p+a1SKqf5dl19 n8DcwQQ4192QIfgEpqq3st736abN3QyXzNxVY211Y2THUJnFNpUczH7W5Z/Xexh3VRpJ SNf9dnpdW9SID+vpgjvGIsbATK2OMBJtGPRVw=
- Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type; b=PAsVnjoZuAsqYzeii1pROkzCmq/MLh9G21Ja8Jqp7qeYxkl8OGbKLtoWY9KSsEBTpA 5eAfFM3hoDyM8zYXptR7PXX5HRz8I9MAH/wMmKkO8DcOjxYDTrU8QUbJnTL59Ao/K/Ey uNxzdxF3BdzfOHfwdhFG12wrIXa2JqpSpzibc=
On Thu, Aug 19, 2010 at 6:51 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
> "The alignment requirement of SIMD memory operands is relaxed."
> ---> wowowowow, does anyone know what they mean here? Sounds important!
yes. Most of the instructions can deal with either two registers or
one memory operand and one register. With SSE the memory operand has
to be 16byte aligned. With AVX there is no particular alignment
requirement, but performance should be affected since there are still
two instructions to load data from memory: an unaligned and an aligned
version and the later require either 16 bytes or 32 bytes depending on
whether you load 16 or 32 bytes....
gael