Re: [eigen] Eigen rocks |

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*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] Eigen rocks*From*: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>*Date*: Fri, 27 Feb 2009 17:26:55 +0100*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type :content-transfer-encoding; bh=54hZSBMjHmHKL69m2GfL2/iTKoi8HctNjxCs5v+OOiI=; b=DRoiqVQs0LKNQIDut9MidxsgS1SFMPf+7pWHYxiLVEK+zt5WoOi+tRQ22K2wjtostR 5qsBjjBYv/EB/nGQmP+0MrYZqbqpT36mMEPv1mEj0BFlVJdueKHyHr/W/km6OyTCUgK+ CG8u887CFiyYj+jbXCto/6DKOaZ+T/UoTfwBg=*Domainkey-signature*: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; b=liPSFHvLZRWUQb0vpyPyIrLHcSnS1piTZzTWYV4pnmoeJj9HfDmm+ixGs6Ray5vsaE VDFZeAnO4MPBKutpcWoqkH52F/HokrW0ZIrQqHZVUPRkJNCVeznQDp6iDrL8uoTt/+Rz Tf0NkYjXErFJnE9R40XUaaqfotXY1nc1KEA4k=

Yes that's what you want for 4). For 3) if you want to access the memory, the data() method returns the pointer to the array of coefficients. For 1), Eigen itself doesn't do any multithreading, but on the plus side, Eigen is stateless so completely (trivially) thread-safe. For 2), that's because these operations are inherently hard to vectorize using standard SIMD instructions, they do not easily split into basic operations such as addition, dot product, etc. I guess a SIMD guru would be able to do something, contributions welcome, but that's not easy at all. Cheers, Benoit 2009/2/27 Ricard Marxer Piñón <email@xxxxxxxxxxxxxxxx>: > I don't know for 1) and 2). I know > > but for 3) and 4) you want the Map class that Eigen provides: > > Search for Map in the tutorial: > http://eigen.tuxfamily.org/dox/TutorialCore.html#TutorialCoreSpecialTopics > > Look at the Map class: > http://eigen.tuxfamily.org/dox/classEigen_1_1Map.html > > or the Map() static functions from the Matrix class: > http://eigen.tuxfamily.org/dox/classEigen_1_1Matrix.html > > > On Fri, Feb 27, 2009 at 5:07 PM, Rohit Garg <rpg.314@xxxxxxxxx> wrote: >> >> Hi all, >> >> To devs and contributors, >> >> EIGEN ROCKS >> >> On a more sober note, >> >> 1) Is eigen multithreaded? I think not because there is no >> documentation on how to decide the number of threads. >> >> 2) Quaternion rotations only take Vector4f, then why are they not >> vectorized? Or is it on the informal todo list. It isn't on the formal >> one. >> >> 3) How do I access the memory hidden behind the class interface of the >> Matrix/Vectors. People may need it to perform some other stuff using >> some other libraries. Eigen is great but doesn't solve all the world's >> problems yet. >> >> 4) And yes it's converse. I wish to set the elements of a >> matrix/vector from a given pointer. Can that be done? >> >> I am pretty sure that 1) and 2) will be done, butt what about 3) and 4). >> >> Regards, >> >> -- >> >> Rohit Garg >> >> http://rpg-314.blogspot.com/ >> >> Senior Undergraduate >> Department of Physics >> Indian Institute of Technology >> Bombay >> >> > > > > -- > ricard > http://www.ricardmarxer.com > http://www.caligraft.com >

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**Re: [eigen] Eigen rocks***From:*Ricard Marxer Piñón

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