[petsc-users] petsc-3.5 quadruple precision mixed with double

[Jed Brown]

Hao Zhang <hbcbh1999 at gmail.com> writes:

> Thanks for the input. I was doing a few tests. I will put quadruple
> precision choice on hold for now. Since the condition number is big at the
> beginning, scale of 10^2, 

That is not large and you don't need quad precision to solve it to
better accuracy than almost any measured physical quantity.

> I will try to smooth the input of the matrix by introducing heaviside
> function.  

Not sure how that is smoothing.

> I do have another question. the incompressible simulation I'm
> simulating is using all reflection(free slip neumann) boundary
> condition, what will be a good preconditioner? Shall I start a new
> thread? so, when other users search, they could use it as a reference

The boundary condition has almost no effect on choice of preconditioner.
There are lots of methods for incompressible flow, many of which can be
implemented at run-time using PCFIELDSPLIT.  Unfortunately, there are
not good black-box solvers, so you'll have to do some reading.
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