[petsc-users] J^T J p calculation

[Isaac, Tobin G]

I don't understand, why don't you just take the dot product of w with itself?

Toby Isaac, Assistant Professor, GTCSE

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From: petsc-users <petsc-users-bounces at mcs.anl.gov> on behalf of Park, Heeho via petsc-users <petsc-users at mcs.anl.gov>
Sent: Thursday, April 9, 2020 3:39:19 PM
To: petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov>
Subject: [petsc-users] J^T J p calculation


Hi PETSc developers,


I am trying to formulate


p^T J^T J p


where p is a solution vector length n, J is Jacobian n-by-n matrix.


Ref: https://en.wikipedia.org/wiki/Gauss%E2%80%93Newton_algorithm under Large-scale optimization


It is known that for parallel computations, the best way to perform this computation (with csr matrix) is


J^T J p = SUM_i [ c_i ( c_i dot p) ] which results in a vector.


In PFLOTRAN, we use mpibaij matrix. I could not find a PETSc command to perform this with one command.

Is there one I couldn't find? if not, is using MATGETROW with C for-loop a good way to do this?

​

I currently use, MatMult(J,p,w); MatMultTranspose(J,w,w2); VecDotRealPart(p,w2);


Best,


Heeho Daniel Park

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Sandia National Laboratories
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