Stephen Crowley wrote:

Is it possible to define a matrix that is part of a larger matrix, without having to create temporaries and copy part of the larger?

/----------\ | | | | SM | | |----| LM | | | \----------/

I need to extract a sub-section of a matrix, multiply it, and then copy it back. I am currently using a temporary, but I have a feeling there must be a better way.

I suppose you are using ublas ;o) `template <typename Matrix> class matrix_range' seems to be what you are looking for: ============================================== using namespace boost::numeric::ublas; matrix<double> LM (10, 10); // init LM matrix<double> M1 (4, 4); // init M1 matrix_range SM (LM, range (1, 5), range (2, 6)); LM = prod (M1, LM); =============================================== matrix_range<> gives you a view of a part (a block) of a matrix. Note that class `range' follows `convention' of iterator ranges: `range (1, 5)' is `[1, 5)', i.e. `1, 2, 3, 4'. There is also function `project()', so there's no need to declare matrix_range<>: =============================================== project (M, range (1, 5), range (2, 6)) = prod (M1, project (M, range (1, 5), range (2, 6))); =============================================== More details on: http://64.226.201.52/libs/numeric/ublas/doc/matrix_proxy.htm#matrix_range Hope this help, fres