[mesa-users] Simple matrix inversion function?

[Warrick Ball]

Hi again, fellow MESA users,

I'm busy modifying the part of the astero module that computes the 
separation ratios (currently r_010 and r_02) so that it will (a) correctly 
incorporate the covariance matrix and (b) also use r_13.

Once this is up and running, I'll post again, but for now, can someone 
tell me how to use the existing MESA subroutines to invert a matrix? 
I've computed the covariance matrix but I need it's inverse to compute the 
chi^2.

I've had a look around the mtx module but, though I can find routines to 
solve matrix equations like A*x=B, I can't seem to find a subroutine to 
invert.  I found the subroutine DGETRI in mtx/lapack_src/dgetri.f and, 
under the impression that this was linked in mtx_lib, I tried adding

   use mtx_lib, only: dgetri

(or DGETRI) in star/astero/src/astero_support.f, but I get a compiler 
error that seems to say that dgetri isn't in mtx_lib.

          use mtx_lib, only: dgetri
                            1
Error: Symbol 'dgetri' referenced at (1) not found in module 'mtx_lib'

I'm pretty sure a relevant routine should be in the MESA or the MESA SDK 
somewhere...

Alternatively, if there's a simple (even if inefficient) way to invert a 
(positive definite) matrix, I can just implement that in the astero 
module.  The inverse only needs to be computed once and only has 
dimensions slightly less than the total number of observed modes (up to 
about 50x50).

Cheers,
Warrick




------------
Warrick Ball
Postdoc, Institut für Astrophysik Göttingen
wball at astro.physik.uni-goettingen.de
+49 (0) 551 39 5069