[petsc-users] Using SNES Shell to create a new solution scheme

[Barry Smith]

   I think the "correct" solution is to introduce a new variable z = a + b; which introduces new equations to that satisfy a + b - z = 0 and then apply bound constraint on z.

    Barry

On Jul 16, 2013, at 7:52 PM, subramanya sadasiva <potaman at outlook.com> wrote:

> Hi, 
> In addition to simple a > 0 and b > 0 constraints at every point in th e domain, I need to apply an additional a + b  < 1 constraint over the domain. The first two , I understand are pretty easy to do using SNES_VI. To apply the third using the approach used in the reduced space approach, I'd need to modify the bounds function to have the linesearch direction available.
> The strategies that seem feasible to me are as follows:
> 1. Program a solver using SNES Shell that does it. 
> 2. Program a linesearch and use SNES Linesearch Shell to solve the problem with a standard SNES VI solver. 
> 3. Modify SNES VI in a local installation.
> 
> To me. it seems that no.2 is the simplest approach. Are any other approaches feasible?
> Thanks, 
> Subramanya