[CIG-MC] ConMan issues report

Scott King sdk at vt.edu
Thu Aug 18 10:57:42 PDT 2016

Yup.    And I remember you putting the direct solver in after our class tests.  Thanks!   

> On Aug 18, 2016, at 1:54 PM, Wolfgang Bangerth <bangerth at tamu.edu> wrote:
> On 08/18/2016 11:46 AM, John Naliboff wrote:
>> I’ll see how this compares to the iterative solver for the 2-D tests I’m
>> running.
> My rule of thumb has always been that direct solvers are really hard to beat for everything with less than 100,000 unknowns. That limit may actually be 200-300,000 today. That's good enough for most 2d problems.
> In 3d, the complexity is different because the size of the front direct solvers have to work through is no longer the N^{1/2} from 2d (in essence, the number of degrees of freedom that are located on a line that sweeps the domain), but N^{2/3} (the number of DoFs that are located on a surface that sweeps the domain). This means far more memory consumption, and far more computations. So in 3d, direct solvers are often not competitive already for much smaller problems.
> Best
> Wolfgang
> -- 
> ------------------------------------------------------------------------
> Wolfgang Bangerth          email:                 bangerth at colostate.edu
>                           www: http://www.math.colostate.edu/~bangerth/
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