OK. Let's look at entry 3,3 in the matrix (ie the last nonzero entry - what matlab would call the 4,4 entry).

Note that the last two entries in mu_bar are zero.

This means that the only nonzero integral in the calculation of this entry is:

\int_{cell 3} 2/dt * phi_3(x) * phi_3(x) * (mu_bar[2] * phi_2(x)) dx

changing coordinates to local we have:

int_0^1 1/det(J) * 2/dt * X * X * (1-X) * mu_bar[2] dX

det(J) = 0.25

dt = L/(Nx*2*pi*sqrt(g*H0)) = 0.04017220189012352

int_0^1 X*X*(1-X) dX = int_0^1 X^2 -X^4 dX = 1/12

1/12 * 2 / dt * 0.25 * mu_bar[2] = 0.20775215537495284

Note that this is the same as the Firedrake result and not the same as the Matlab code. I therefore claim that the problem is in the Matlab code, and not a bug in Firedrake

Regards,

David

On Wed, 8 Jun 2016 at 14:44 Anna Kalogirou <a.kalogirou@leeds.ac.uk> wrote:

Yes, it is correct. In that code I define a very small mesh just to inspect the values of the matrix. The same variables in Matlab are:

mu_bar =

   0.346930948820870
   0.283267933530252
   0.200300676691942
                   0
                   0

B_mu =

   (1,1)      1.377548049348976
   (2,1)      0.655870455292249
   (1,2)      0.655870455292249
   (2,2)      2.344153409095711
   (3,2)      0.506503005236205
   (2,3)      0.506503005236205
   (3,3)      1.641943147430029
   (4,3)      0.280003094180926
   (3,4)      0.280003094180926
   (4,4)      0.405861612962805

You can see that even though mu_bar is the same as the one obtained from firedrake, the matrix entries are different. I don't understand why.. The rest of the matrices, i.e. M, A and C_lam, have the same entries as in firedrake.

Thanks,

Anna.
On 08/06/16 14:38, Fabio Luporini wrote:
Hello Anna,

under the Inequality constraint folder, I'm running "python buoy-swe.py" and, besides the TSFC/COFFEE prints, I'm obtaining:

mu_bar

------

[ 0.34693095 0.28326793 0.20030068 0. -0. ]

Matrix b_mu

-----------

[[ 1.37331778 0.6536432 0. 0. 0. ]

[ 0.6536432 2.33042494 0.50155807 0. 0.]

[ 0. 0.50155807 1.54031885 0.20775216 0.]

[ 0. 0. 0.20775216 0.20775216 0. ]

[ 0. 0. 0. 0. 0. ]]

What values do you expect for b_mu ? Am I running the right thing?

I tried switching off some optimisations but I still get the same output.

Thanks!

-- Fabio
2016-06-08 15:16 GMT+02:00 Anna Kalogirou <a.kalogirou@leeds.ac.uk>:
Hi Fabio,

Sorry for that. It should be public now.

Anna.

On 08/06/16 13:56, Fabio Luporini wrote:
Hello Anna,

the code is not accessible as it appears to be in a private repository. Could you fix this? Thanks

-- Fabio
2016-06-08 14:10 GMT+02:00 Anna Kalogirou <a.kalogirou@leeds.ac.uk>:
Dear all,

I have a simple question regarding a matrix assembly in Firedrake which I believe is not computed correctly.

The relevant code can be found here and the issue is with the B_mu matrix in solvers.py, line 51. I compare the result with my own Matlab code and the two don't agree. Also, the rest of the matrices M, A, C_lam agree in both sets of code.

Can someone help with what the problem might be?

Thanks,

Anna.

-- Dr Anna Kalogirou Research Fellow School of Mathematics University of Leeds http://www1.maths.leeds.ac.uk/~matak/
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