[Trilinos-Users] a request
dmday at sandia.gov
Tue Nov 4 09:32:43 MST 2008
Dear Jules Gilbert,
Do you mean that you wish to determine a matrix with specified row and
column sums? You don't need Trilinos for that.
Let e denote the m column vector of ones and let apostrophe denote
transposition. One solution is
A = x e' + e y' + a e e'
where x and y are vectors orthogonal to e, and a is a scalar. The
scalar a is the sum of the row sums, or the sum of the column sums
(which must coincide). Just read off x and y from
x = (A- a e e') (e/m), y = (A'- a e e') (e/m)
On Mon, 2008-11-03 at 20:19 -0700, Jules Gilbert wrote:
> Hi; I've been quiet, but subscribed to the Trilinos group for some time.
> Now I have a question. I have an M * M matrix. (Always a matrix,
> never merely rectangular.) I have 2*M values, the sums along the
> length and width of the edges.
> I realize that depending on the size of M, such a system may be
> seriously underdetermined. (Only M=2 is exactly determined.) I want
> to produce code, in C, that I can use to best approximate the values
> of each of the M*M cells.
> Please email me; I am just.stocks at gmail.com
> And thank you.
> Trilinos-Users mailing list
> Trilinos-Users at software.sandia.gov
More information about the Trilinos-Users