Re: [ublas] Assignement of a matrix with a pointer to the matrix data !?

From: Gunter Winkler (guwi17_at_[hidden])
Date: 2008-02-04 17:32:55

rustinc schrieb:
> Hi, I'm a new Ublas user.
> I wish to do the following thing: I want to create a new matrix specifying its 
> size (m rows, n columns) and a pointer to the data contained in the matrix.  
> These data naturally fit the UBLAS storage. It is maybe a little bit strange 
> but I necessary need this functionality. 
> I explain why...
> In fact I implement a program in which two processes run in parallel (thanks 
> to pthreads,shared memory or MPI). It exists some common interface between 
> the two processes. In the first process a UBLAS matrix is created and 
> assigned, the interface is created and it contains the matrix data. The other 
> process knows the size of the matrix but I really don't wish to copy the data 
> of the interface in a new matrix. The size of the interface is really big and 
> the update of the quantities at the interface occurs very often. 
> I assume it exists in the vector/matrix class a pointer to the data. If yes 
> what? May I to assigned it? Or is it protected???
> How have I to do?
>
>   
The answer is to use array adaptors. (Look for 'array adaptor' in the 
archive). If you only need read only access, you can use my read only 
adaptor.

http://guwi17.de/ublas/examples/

uBlas additionally supports carray_adaptor and shallow_array_adaptor.

see http://www.boost.org/libs/numeric/ublas/doc/array_adaptor.htm

However, I suggest to read the comments in storage.hpp and on this list 
before you try to modify matrices based on adaptors.

mfg
Gunter