sum and inversion of matrix

[smile23]

hello!
is there a intrinsic function for the sum of arrays?..and for the inversion of a matrix?
thanks

 

[FJacq]

For the sum : simply +

For the inversion, you need a dedicated library like LAPACK which provides many methods depending on your matrix.

 

[xwb]

You could use sum to sum the elements of a matrix/array.

Question: why do you need the inverse? Is it to solve simultaneous equations? If it is, it would be faster to use Choleski LU decomposition than matrix inversion.

 

[GerritGroot]

I agree with xwb that LU is faster. There are many many methods to do this job, upto Gauss-Seidel.

A good explanation with fortran 77 codes included can be found at the numerical recipes page.

http://www.nrbook.com/a/bookfpdf.php

Reading chapter 2, you can judge for yourself about the best method and code it (the given codes are short and handy and don't need any library, I used to translate that given codes to F90 when needed).

P.S.: As far as I remember, Cholesky is a restrictive form of LU for symmetric matrices only