Jed,

On Nov 21, 2012, at 12:09 PM, Jed Brown wrote:

> On Wed, Nov 21, 2012 at 9:03 PM, Gautam Bisht <gbisht at lbl.gov> wrote:
> I need to compute an inverse of M, a small matrix (3x3), and am coding in 
> Fortran 90. Following the suggestion under FAQ on the website, I'm trying to 
> use MatMatSolve to obtain the inverse of matrix. I did the following:
> 
> - Created three sequential dense matrices: M, I, Minv
> - Filled values in M and I using MatSetValues
> - Tried factoring Matrix M before calling MatMatSolve(M,I,Minv,ierr)
> 
> I'm not sure what arguments needs to be passed as arguments in MatLUFactor() 
> corresponding to IS row, IS col, and MatFactorInfo. I noticed the following 
> note on website that states "Developer Note: fortran interface is not 
> autogenerated as the f90 interface defintion cannot be generated correctly 
> [due to MatFactorInfo]".
> Is there a Fortran90 example demonstrating the use of MatMatSolve()?
> 
> For a 3x3 matrix, you should just use the explicit formula for the inverse. 
> Going through the PETSc interface doesn't make sense at all.

The 3x3 matrix is being generated using MatMult of 3xN and Nx3 matrices. I 
wanted to give MatMatSolve a try, but could not figure how to use it via 
Fortran. I will now code up the explicit formula.

>  
> 
> Additionally, I have been trying to update my copy of petsc-dev, and am 
> getting timed out from the server. 
> 
> The server died so it has moved to https://bitbucket.org/petsc/petsc-dev.


-Gautam.
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