Re: [eigen] Comparing notes on work by Igleberger et al. 2012 |

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*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] Comparing notes on work by Igleberger et al. 2012*From*: Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>*Date*: Tue, 28 Aug 2012 17:14:48 +0200

On 28.08.2012 16:39, Gael Guennebaud wrote:

On Tue, Aug 28, 2012 at 4:24 PM, Rhys Ulerich <rhys.ulerich@xxxxxxxxx> wrote:[...]Partly. Blaze is also able to exploit AVX instruction (so a theoretical x2 compared to SSE), however Blaze suffers from a HUGE shortcoming: data are assumed to be perfectly aligned, including inside a matrix. For instance, a row-major matrix is padded with empty space such that each row is aligned. The extra space *must* be filled with zeros and nothing else because they are exploited during some computations... As a consequence, Blaze does not has any notion of sub-matrices or the like, cannot map external data, etc. One cannot even write a LU decomposition on top of Blaze. In other word, it is not usable at all. This is also unfair regarding the benchmarks because they are comparing Blaze with perfectly aligned matrices to Eigen or MKL with packed and unaligned matrices.

2) Blaze shows faster performance on A*B*v for A and B matrices because they don't honor order of operations and their expression templates treat it as A*(B*v). This is moot as I can simply write A*(B*v) in Eigen.Exactly, though we plane to do the same (and more) once the evaluators finalized.

I wouldn't see how they can do it with methods like (Eigen syntax): void aliastest(VectorXd& res, const VectorXd &x){ res = {some complex expression with x}; } Christoph -- ---------------------------------------------- Dipl.-Inf. Christoph Hertzberg Cartesium 0.049 Universität Bremen Enrique-Schmidt-Straße 5 28359 Bremen Tel: +49 (421) 218-64252 ----------------------------------------------

**Follow-Ups**:**Re: [eigen] Comparing notes on work by Igleberger et al. 2012***From:*Gael Guennebaud

**References**:**[eigen] Comparing notes on work by Igleberger et al. 2012***From:*Rhys Ulerich

**Re: [eigen] Comparing notes on work by Igleberger et al. 2012***From:*Gael Guennebaud

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