RE: [Libmesh-users] infinite elements & complex fields

[KIRK, B. (JSC-E. (NASA) <ben...@na...>]

While configuring PETSc and all its dependencies it not exactly
straightforward, once it is functional it should be trivial to use libMesh
with it.  Laspack, at least for real numbers, should be pretty safe too, but
it does not do as much error-checking as PETSc.  The complex support in
laspack was added by Daniel a couple of years ago and hasn't received as
much testing.

-Ben



-----Original Message-----
From: lib...@li...
[mailto:lib...@li...] On Behalf Of Rolf Mueller
Sent: Saturday, March 26, 2005 2:17 PM
To: Steffen Petersen; lib...@li...
Subject: Re: [Libmesh-users] infinite elements & complex fields


Dear Steffen,

thank you so much again for your kind help.

On Thu, Mar 24, 2005 at 06:46:39PM +0100, Steffen Petersen wrote:
 
> The problem is somehow related to laspack. When using PETSc everything 
> works fine and I get reasonable results.

OK, what an irony: I had chosen laspack, because I had - wrongly - assumed
that it would be the least error-prone. Now I am using PETSc (configuration
"--enable-petsc --enable-complex --enable-mpi") and I think it works: The
spherical symmetry of the solution looks very good in general and was
perfect where I tested it (along the x-axis).

Here are some example results for the real part of the solution along the
x-axis:

    x         ex6       cos(x)/(4*pi*x)
         0    6.5665       Inf
    0.0667    0.6505    1.1910
    0.1333    0.6000    0.5915
    0.2000    0.3743    0.3900
    0.2667    0.2840    0.2879
    0.3333    0.2231    0.2256
    0.4000    0.1818    0.1832
    0.4667    0.1514    0.1523
    0.5333    0.1278    0.1285
    0.6000    0.1090    0.1095
    0.6667    0.0934    0.0938
    0.7333    0.0803    0.0806
    0.8000    0.0691    0.0693
    0.8667    0.0592    0.0594
    0.9333    0.0506    0.0507
    1.0000    0.0214    0.0430

So it seems that - away from the singularity - the accuracy of the solution
is pretty good, but it deteriorates at the node which is shared with the
infinite element (at x=1). - Is that a necessity, BTW?

Thank you once more.

Happy Easter,
Rolf


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