[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Mark a matrix "upper" in a oct-file

From: Marco Caliari
Subject: Re: Mark a matrix "upper" in a oct-file
Date: Mon, 8 Sep 2014 12:26:52 +0200 (CEST)
User-agent: Alpine 2.10 (DEB 1266 2009-07-14)

On Fri, 5 Sep 2014, David Bateman wrote:

Le 5 sept. 2014 à 13:56, Marco Caliari <address@hidden> a écrit :

Dear all,

I have to take the upper triangular part of a matrix in a oct-file. Later, I 
have to perform RowVector-Matrix products with it. This is my code

// given Matrix F(m,m)
// take the upper triangular part
for (octave_idx_type j = 0; j < m; j++)
     for (octave_idx_type i = j+1; i < m; i++)
   F(i,j) = 0.0;
 RowVector d = F.row(0);
// make RowVector-matrix products
 for (octave_idx_type i = 0; i < s-1; i++)
   d = d * F;

My question is: if I mark the matrix "upper" (but do not know how to do it), is 
the RowVector-Matrix product faster (for instance BLAS dtrmv is used instead of general 

Look at the matrix_type function for how to mark the matrix as upper. However, 
marking it as such is only useful at this point for the solve function or slash 

Thanks David,

I do not know how to use matrix_type in a oct file, but I understand it is useless to my purpose. It seems that Matlab does not use dtrmv for triangular matrices, too (I see the same cputime). Nevertheless, it could be an interesting new feature in Octave, maybe not so difficult to implement.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]