Hi Lukasz, thanks for sharing very interesting slide.
Both of you are right, the mortar method starts from continuum argument
then reduce to discrete space by discretizing the Lagrange multiplier.
However, the way to choose the interpolation space has some implication on
the properties of the mort
On Wed, May 3, 2017 at 2:29 AM, Hoang Giang Bui wrote:
> Dear Jed
>
> If I understood you correctly you suggest to avoid penalty by using the
> Lagrange multiplier for the mortar constraint? In this case it leads to the
> use of discrete Lagrange multiplier space.
>
Sorry for being ignorant here
On 3 May 2017, at 08:29, Hoang Giang Bui
mailto:hgbk2...@gmail.com>> wrote:
Dear Jed
If I understood you correctly you suggest to avoid penalty by using the
Lagrange multiplier for the mortar constraint? In this case it leads to the use
of discrete Lagrange multiplier space. Do you or anyone
On Wed, 3 May 2017 at 09:29, Hoang Giang Bui wrote:
> Dear Jed
>
> If I understood you correctly you suggest to avoid penalty by using the
> Lagrange multiplier for the mortar constraint? In this case it leads to the
> use of discrete Lagrange multiplier space. Do you or anyone already have
> exp
Dear Jed
If I understood you correctly you suggest to avoid penalty by using the
Lagrange multiplier for the mortar constraint? In this case it leads to the
use of discrete Lagrange multiplier space. Do you or anyone already have
experience using discrete Lagrange multiplier space with Petsc?
The
Thanks Barry
Running with that option gives the output for the first solve:
BoomerAMG SETUP PARAMETERS:
Max levels = 25
Num levels = 7
Strength Threshold = 0.10
Interpolation Truncation Factor = 0.00
Maximum Row Sum Threshold for Dependency Weakening = 0.90
Coarsening Type =
> On Apr 29, 2017, at 8:34 AM, Jed Brown wrote:
>
> Hoang Giang Bui writes:
>
>> Hi Barry
>>
>> The first block is from a standard solid mechanics discretization based on
>> balance of momentum equation. There is some material involved but in
>> principal it's well-posed elasticity equation w
Hoang Giang Bui writes:
> Hi Barry
>
> The first block is from a standard solid mechanics discretization based on
> balance of momentum equation. There is some material involved but in
> principal it's well-posed elasticity equation with positive definite
> tangent operator. The "gluing business"
Hi Barry
The first block is from a standard solid mechanics discretization based on
balance of momentum equation. There is some material involved but in
principal it's well-posed elasticity equation with positive definite
tangent operator. The "gluing business" uses the mortar method to keep the
c
Ok, so boomerAMG algebraic multigrid is not good for the first block. You
mentioned the first block has two things glued together? AMG is fantastic for
certain problems but doesn't work for everything.
Tell us more about the first block, what PDE it comes from, what
discretization, and wh
It's in fact quite good
Residual norms for fieldsplit_u_ solve.
0 KSP Residual norm 4.014715925568e+00
1 KSP Residual norm 2.160497019264e-10
Residual norms for fieldsplit_wp_ solve.
0 KSP Residual norm 0.e+00
0 KSP preconditioned resid norm 4.014715925568e+00 tru
Run again using LU on both blocks to see what happens.
> On Apr 27, 2017, at 2:14 AM, Hoang Giang Bui wrote:
>
> I have changed the way to tie the nonconforming mesh. It seems the matrix now
> is better
>
> with -pc_type lu the output is
> 0 KSP preconditioned resid norm 3.308678584240e
I have changed the way to tie the nonconforming mesh. It seems the matrix
now is better
with -pc_type lu the output is
0 KSP preconditioned resid norm 3.308678584240e-01 true resid norm
9.006493082896e+06 ||r(i)||/||b|| 1.e+00
1 KSP preconditioned resid norm 2.004313395301e-12 tru
This can happen in the matrix is singular or nearly singular or if the
factorization generates small pivots, which can occur for even nonsingular
problems if the matrix is poorly scaled or just plain nasty.
> On Apr 24, 2017, at 5:10 PM, Hoang Giang Bui wrote:
>
> It took a while, here I
It took a while, here I send you the output
0 KSP preconditioned resid norm 3.129073545457e+05 true resid norm
9.015150492169e+06 ||r(i)||/||b|| 1.e+00
1 KSP preconditioned resid norm 7.442444222843e-01 true resid norm
1.003356247696e+02 ||r(i)||/||b|| 1.112966720375e-05
2 KSP pr
> On Apr 24, 2017, at 12:47 PM, Hoang Giang Bui wrote:
>
> Good catch. I get this for the very first step, maybe at that time the rhs_w
> is zero.
With the multiplicative composition the right hand side of the second solve
is the initial right hand side of the second solve minus A_10*x wh
Good catch. I get this for the very first step, maybe at that time the
rhs_w is zero. In the later step, it shows 2 step convergence
Residual norms for fieldsplit_u_ solve.
0 KSP Residual norm 3.165886479830e+04
1 KSP Residual norm 2.905922877684e-01
Residual norms for fieldsplit_wp_ s
> On Apr 24, 2017, at 3:16 AM, Hoang Giang Bui wrote:
>
> Thanks Barry, trying with -fieldsplit_u_type lu gives better convergence. I
> still used 4 procs though, probably with 1 proc it should also be the same.
>
> The u block used a Nitsche-type operator to connect two non-matching domains.
Thanks Barry, trying with -fieldsplit_u_type lu gives better convergence. I
still used 4 procs though, probably with 1 proc it should also be the same.
The u block used a Nitsche-type operator to connect two non-matching
domains. I don't think it will leave some rigid body motion leads to not
suff
> On Apr 23, 2017, at 2:42 PM, Hoang Giang Bui wrote:
>
> Dear Matt/Barry
>
> With your options, it results in
>
> 0 KSP preconditioned resid norm 1.106709687386e+31 true resid norm
> 9.015150491938e+06 ||r(i)||/||b|| 1.e+00
> Residual norms for fieldsplit_u_ solve.
> 0
Dear Matt/Barry
With your options, it results in
0 KSP preconditioned resid norm 1.106709687386e+31 true resid norm
9.015150491938e+06 ||r(i)||/||b|| 1.e+00
Residual norms for fieldsplit_u_ solve.
0 KSP Residual norm 2.407308987203e+36
1 KSP Residual norm 5.797185652683e
Huge preconditioned norms but normal unpreconditioned norms almost always
come from a very small pivot in an LU or ILU factorization.
The first thing to do is monitor the two sub solves. Run with the additional
options -fieldsplit_u_ksp_type richardson -fieldsplit_u_ksp_monitor
-fieldsp
On Sun, Apr 23, 2017 at 12:22 PM, Hoang Giang Bui
wrote:
> Hello
>
> I encountered a strange convergence behavior that I have trouble to
> understand
>
> KSPSetFromOptions completed
> 0 KSP preconditioned resid norm 1.106709687386e+31 true resid norm
> 9.015150491938e+06 ||r(i)||/||b|| 1.00
Hello
I encountered a strange convergence behavior that I have trouble to
understand
KSPSetFromOptions completed
0 KSP preconditioned resid norm 1.106709687386e+31 true resid norm
9.015150491938e+06 ||r(i)||/||b|| 1.e+00
1 KSP preconditioned resid norm 2.933141742664e+29 true resi
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