Hi all,

I am evaluation eigen for future project. One simple question that I cannot figure out is how one can fill a matrix give an array of double (in column/row major order).

Any pointer is appreciated.

Use the Map class to map your existing double* array as a Eigen expression.

http://eigen.tuxfamily.org/dox/classEigen_1_1Map.html

EDIT: hm OK the documentation there isn't too friendly so have a look at the tutorial:
http://eigen.tuxfamily.org/dox/TutorialCore.html
(search for "Map" in that page)

Nice, that helps.

One more follow up question. Suppose that the memory buffer is not cache aligned with the eigen standard, would the vectorisation still be performed?

Thanks.

For dynamic-size expressions (for example Map<MatrixXf>), yes. Eigen will then, at runtime, do the first few scalars separately until the first 16-byte-aligned location, and will continue with SIMD packets from there on.

For fixed-size expressions (for example Map<Matrix4f>), no.

If you happen to know that the pointer is 16-byte aligned, then, with the development branch (not Eigen 2.0) you can tell that to Eigen: Map<Matrix4f, Aligned>.